Wilkinson, A.J., & Yang, L., (2014). Long-term maintenance of inhibition training effects in older adults: 1- and 3-year follow-up. Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, doi:10.1093/geronb/gbu179
Long-Term Maintenance of Inhibition Training Effects in Older Adults: 1- and 3-Year Follow-Up Andrea J. Wilkinson and Lixia Yang Department of Psychology, Ryerson University, Toronto, Ontario, Canada.
Methods. Participants from an original 6-session Stroop training study (Wilkinson & Yang, 2012 [Wilkinson, A. J., & Yang, L. (2012). Plasticity of inhibition in older adults: Retest practice and transfer effects. Psychology and Aging, 27, 606–615. doi:10.1037/a0025926]) were invited to come back to the lab to complete a single session of the Stroop task at 2 different time points. Thirty-three older adults returned for the 1-year follow-up session, and 26 of them returned for the 3-year follow-up session. Results. The results revealed maintenance of the training-induced inhibition gains at both follow-up sessions. Furthermore, performance at the 2 follow-up sessions was better (i.e., reduced Stroop ratio interference score) than baseline level. Discussion. The findings demonstrate the durability of inhibition training gains in older adults for up to a 3-year period. These results further extend the literature on long-term maintenance of cognitive training benefits in older adults by examining the durability of training effects in inhibition, an important executive function, and by covering a substantial maintenance period (i.e., up to 3 years). Key Words: Aging—Durability—Executive function—Inhibition—Long-term maintenance.
Background The evaluation of long-term maintenance following cognitive training is important because it demonstrates endurance of the learning induced by the initial training. Previous literature has shown that older adults are able to maintain cognitive training effects for long periods of time, ranging from several months (e.g., Borella, Carretti, Riboldi, & De Beni, 2010; Brehmer, Westerberg, & Bäckman, 2012; Dahlin, Nyberg, Bäckman, & Neely, 2008; Günther, Schäfer, Holzner, & Kemmler, 2003; Kramer, Hahn, & Gopher, 1999; Li et al., 2008; Yang & Krampe, 2009) all the way up to several years (Ball et al., 2002; Rebok et al., 2014; Stigsdotter Neely & Bäckman, 1993; Willis & Nesselroade, 1990; Willis et al., 2006). For example, in the Advanced Cognitive Training for Independent and Vital Elderly study, training gains in reasoning and speed of processing, but not memory, were demonstrated to be maintained at or above baseline level 10 years after original training, with the inclusion of booster sessions at, approximately, 1 and 3 years (Rebok et al., 2014). In a recent systematic review and meta-analysis (Kelly et al., 2014), it was suggested that booster sessions (as well as an adaptive training protocol) could enhance the maintenance of training effects. However, not all cognitive training follow-up studies include booster sessions (e.g., Borella et al., 2010; Brehmer et al., 2012; Dahlin et al., 2008; Li et al., 2008; Stigsdotter Neely & Bäckman, 1993). For example, following memory
training, older adults were able to maintain the performance gain over baseline level for 3.5 years—in the absence of any booster training sessions (Stigsdotter Neely & Bäckman, 1993). So, the benefit of booster sessions is still debated in the literature. In this study, we examined the longitudinal benefits of inhibition training without any booster sessions. The durability of training gains in older adults has been demonstrated in a variety of cognitive domains, including memory, reasoning, perceptual-motor speed, and visual attention (Günther et al., 2003; Rebok et al., 2014; Stigsdotter Neely & Bäckman, 1993; Willis & Nesselroade, 1990; Willis et al., 2006; Yang & Krampe, 2009). It has also been shown in training with executive functions, such as updating (Dahlin et al., 2008; Li et al., 2008). However, to our knowledge, little has been done to examine the longterm maintenance of training gains in inhibition, one type of executive function, among older adults. This study serves to fill this gap. Examining the durability of executive function training is important, especially among older adults, because executive functions have been identified as critical for the effective completion of activities of daily living (Gross, Rebok, Unverzagt, Willis, & Brandt, 2011). Inhibition, in particular, is an executive ability that functions to regulate attention and keep cognitive processing in line with task goals (Harnishfeger, 1995; Hasher, Zacks, & May, 1999; Logan, 1994). A considerable amount of literature has
© The Author 2015. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: [email protected]. Received May 12, 2014; Accepted December 3, 2014 Decision Editor: Myra Fernandes, PhD
Page 1 of 8
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
Objectives. The aim of this study is to examine the long-term maintenance of training benefits in inhibition, as measured with the Stroop task, in older adults over 1- and 3-year periods.
Page 2 of 8
WILKINSON AND YANG
the remaining received individualized and adaptive feedback based on their performance on previous trials at the end of each trial (for additional details, see Wilkinson & Yang, 2012). Finally, the standard Block 4 followed the same trial procedure, but without any feedback in order to provide a fair comparison across the feedback groups in the analysis of training benefits. The results demonstrated improvements in inhibition, as indexed by reduced Stroop interference scores (i.e., difference scores calculated between incongruent and neutral trials), across the six training sessions. Interestingly, this effect was equivalent across all three feedback groups, suggesting that the type and amount of externally generated feedback did not modulate the magnitude of training-induced improvements in inhibition. As a long-term maintenance follow-up, this study tested returning participants from the original study by Wilkinson and Yang (2012) at 1 and 3 years following the original training. In an effort to control for general slowing with aging in the Stroop interference effect, we followed the approach used in some recent meta-analyses (Schwartz & Verhaeghen, 2008; Verhaeghen, 2011) and calculated a Stroop ratio interference score by dividing the RT of incongruent trials by that of the neutral trials (incongruent RT/neutral RT). The ratio score indexes the cost of responding to the executive control (incongruent) condition as a proportion of baseline speed in color naming (neutral condition). This score controls for agerelated changes in general processing speed (Schwartz & Verhaeghen, 2008; Verhaeghen, 2011), and thus provides a more accurate measure of inhibitory efficiency relative to a simple difference score (incongruent RT – neutral RT). In this study, we first used the ratio score to re-examine the original training effects in Wilkinson and Yang (2012), then we used it to evaluate maintenance of the training gains over 1- and 3-year periods. This allowed us to assess training-induced performance changes that were specific to interference, while taking fluctuations in response speed across sessions into consideration. In light of previous long-term maintenance training studies that cover comparable duration periods (e.g., 18 months in Dahlin et al., 2008; and 3.5 years in Stigsdotter Neely & Bäckman, 1993), we expect that the original training gain will be maintained at both follow-up sessions, where performance will continue to exceed baseline performance level. Method Participants The original training sample in Wilkinson and Yang (2012) consisted of 42 older adults (28 women, age range = 60–84 years; mean [M] = 70.98, standard deviation [SD] = 6.42) recruited from the internal Ryerson Senior Participant Pool. Given the lack of feedback
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
consistently shown age-related deficits in inhibition (Biss, Campbell, & Hasher, 2013; Bojko, Kramer, & Peterson, 2004; Butler & Zacks, 2006; Gazzaley, Cooney, Rissman, & D’Esposito, 2005; Hamm & Hasher, 1992; Hasher et al., 1999; Hasher, Lustig, & Zacks, 2007; Nieuwenhuis, Ridderinkhof, de Jong, Kok, & van der Molen, 2000; Rowe, Valderrama, Hasher, & Lenartowicz, 2006; Yang & Hasher, 2007). In literature, one commonly used inhibition measure is the Stroop task. In a typical Stroop task, participants are instructed to name the ink color in which a color word is printed (e.g., RED printed in blue ink, respond blue). There are three types of Stroop stimuli: congruent (e.g., “GREEN” in green ink, respond green), incongruent (e.g., “GREEN” in blue ink, respond blue), and neutral (e.g., “XXXXX” in green ink, respond green; Wilkinson & Yang, 2012—adapted from Stroop [1935]). On incongruent trials, there is a conflict between the color word and ink color of the stimulus; therefore, participants must suppress the automatic word reading response in order to correctly identify the ink color of the stimulus. Encouragingly, some previous work has demonstrated plasticity, defined as training-induced improvement (Baltes & Lindenberger, 1988), of inhibition among older adults using the Stroop task within a single session or across two sessions (e.g., Davidson, Zacks, & Williams, 2003; Dulaney & Rogers, 1994). Going beyond the literature, Wilkinson and Yang (2012) demonstrated sizable plasticity of inhibition, after controlling for item-specific effects, across six training sessions among older adults. This study serves as a follow up to Wilkinson and Yang (2012), aiming to assess the long-term maintenance of the inhibition training effects across 1- and 3-year periods. In the original work by Wilkinson and Yang (2012), 42 healthy older adults (aged 60–84), evenly divided into three feedback groups, completed a 2-week training program on the Stroop task. Each week involved three training sessions. At each session, participants completed four blocks of Stroop task trials (i.e., key-color acquisition, practice, training, and standard). The purpose of the keycolor acquisition block was to familiarize participants with the mapping scheme between the response keys and colors. During this block, participants received accuracy feedback after each trial. The purpose of practice Block 2 was to familiarize participants with the trial procedure of the upcoming training Block 3. In this way, only those participants in the individualized and adaptive feedback group received the corresponding feedback, whereas other participants did not receive any feedback at all. The training Block 3 followed the same procedure as practice Block 2 except that participants received the full manipulation of feedback, such that some participants did not receive any feedback (i.e., no-feedback control), some others received summary feedback on the average reaction time (RT) and accuracy at the end of the block, and
Page 3 of 8
LONG-TERM MAINTENANCE OF INHIBITION TRAINING
all other participants (98.5%) at the 3-year follow-up session. Therefore, this participant was included in the final analyses. Materials and Procedure At each follow-up session, a similar trial procedure as the one implemented in Wilkinson and Yang (2012) was adopted; however, participants were not trained (i.e., they did not receive any feedback on performance in any of the blocks). In particular, participants completed four blocks of the Stroop task: key-color acquisition (Block 1: 40 trials); practice (Block 2: 24 trials); training (Block 3: 216 trials); and standard (Block 4: 144 trials). Blocks 1 and 2 followed the same trial procedure, except that accuracy feedback was provided in Block 1, but not in Block 2. The training Block 3 and standard Block 4 were named as such for consistency with the terminology used in the original study by Wilkinson and Yang (2012). Critically, and different from the original study in which feedback was manipulated during the training Block 3, no feedback was provided for any of the participants in this block at the two follow-up sessions. As a result, Blocks 3 and 4 followed the same trial procedure, both without feedback, at the two follow-up sessions. In the original study, there were two counterbalance conditions in which the set of colors used for the Stroop task varied across sessions. This was done to minimize item-specific effects (for additional details, see Wilkinson & Yang, 2012). At both follow-up sessions, participants completed
Table 1. Returned Versus Not Returned Participant Demographic Characteristics and Baseline Cognitive Performance Assessed at Pretest 1-Year follow-up Characteristic Age (years) Gender (women, n)a Education (years) Health Visual acuity Short blessed test BAI Shipley Go-No Go Digit symbol Letter series ANT Alerting Orienting Exec control Task-switching task
3-Year follow-up
Returned (n = 33)
Not returned (n = 9)
d
Returned (n = 26)
Not returned (n = 15)
71.12 (6.52) 21 16.27 (3.44) 8.48 (0.97) 31.52 (8.61) 1.06 (1.62) 6.88 (6.39) 36.70 (3.27) 6.52 (3.81) 61.52 (12.85) 9.67 (4.42)
70.44 (6.39) 7 15.11 (4.76) 8.61 (1.11) 36.11 (15.16) .44 (1.33) 7.11 (5.95) 34.67 (5.41) 7.11 (6.41) 54.56 (11.84) 8.44 (4.28)
.78 .43 .42 .74 .24 .30 .92 .16 .72 .15 .46
p Value
0.11 — 0.28 0.12 0.37 0.42 0.04 0.45 0.11 0.56 0.28
69.81 (5.91) 16 16.34 (3.52) 8.58 (0.95) 31.35 (9.33) .96 (1.46) 7.31 (6.72) 36.31 (3.40) 5.85 (3.26) 62.15 (11.28) 10.12 (4.35)
72.60 (7.10) 11 15.40 (4.22) 8.50 (1.05) 34.67 (12.17) .93 (1.83) 6.53 (5.60) 36.00 (4.69) 8.07 (5.87) 55.53 (14.64) 8.27 (4.43)
.18 .44 .45 .81 .33 .96 .71 .81 .13 .11 .20
p Value
0.43 — 0.24 0.08 0.31 0.02 0.13 0.08 0.47 0.51 0.42
28.32 (42.41) 81.53 (42.60) 114.66 (50.68) 16.76 (236.86)
31.97 (30.70) 55.02 (27.71) 95.91 (71.21) 39.93 (115.14)
.81 .08 .37 .78
0.10 0.74 0.30 0.12
34.07 (38.61) 86.47 (41.78) 111.80 (48.13) 38.56 (179.63)
26.78 (36.13) 54.19 (28.92) 99.72 (58.37) .18 (276.59)
.56 .01* .48 .59
0.19 0.90 0.23 0.16
d
Notes. BAI = Beck’s Anxiety Inventory; Shipley = Shipley Vocabulary Test; ANT = Attention Network Test (alerting, orienting, exec control = executive control). Mean scores with standard deviations presented in parentheses for each cell (except for gender). Education was indexed by the average number of years of formal education; health was indexed by a self-report score out of 10; visual acuity was indexed by the near visual acuity score from the Rosenbaum Visual Acuity Pocket Screener (score 20/—); digit symbol, letter series, and Shipley were scored by the average number of correct solutions; average scores were displayed for BAI and short blessed test; Go-No Go was scored by the average number of false alarms; ANT (alerting, orienting, and executive control) and the task-switching task were scored by a difference reaction time score in milliseconds. — = not applicable; d = Cohen’s d effect size calculation for between subjects. p Values are from independent t tests comparing “Returned” to “Not returned” at each follow-up session. a Denotes the use of chi-square statistics. *p < .05.
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
effects in the original training study, as well as the small sample size per feedback group at each follow-up session, the data presented were collapsed across feedback conditions. The 1-year follow-up sample.—Thirty-three of the 42 participants from the original sample returned for the 1-year follow-up session (21 women, age range = 60–84 years, M = 71.12, SD = 6.52). Table 1 displays details of the demographic information and baseline cognitive performance collected at the pretest session of the original training study. The detailed analysis and results on the attrition effects are presented in the Results section. The 3-year follow-up sample.—One participant was accidentally tested 2 years after the original training. This individual was excluded from the final analyses reported below. Twenty-six of the 33 participants who were tested at the 1-year follow-up session returned for the 3-year follow-up session (16 women, age range = 60–80 years, M = 69.81, SD = 5.91). The attrition effects were analyzed in the same way as for the 1-year follow-up sample (see the Results section for details). At the 3-year follow-up session, color blindness was assessed using the Dvorine Pseudo-Isochromatic Plates (Dvorine 1953). One participant was suspected for possible color blindness, as indicated by difficulty in answering five items on the Dvorine Pseudo-Isochromatic Plates test. This individual, however, showed a similar and acceptable average accuracy score (90.3%) on the Stroop task, compared with
Page 4 of 8
WILKINSON AND YANG
Results All statistical analyses were conducted using SPSS 20. Attrition Effects To determine the selective attrition effects, we compared participants who returned for the follow-up sessions and those who opted not to return on baseline cognitive measures and demographic variables using independent t tests (see Table 1). The following outcome variables were involved in these analyses: age, gender, years of education, self-reported health rating, visual acuity (as measured with the Rosenbaum Pocket Vision Screener; Rosenbaum, 1976), cognitive impairment (as assessed with the Short Blessed Test; Katzman et al., 1983), anxiety (as measured with the Beck Anxiety Inventory; Beck, Epstein, Brown, & Steer, 1988), vocabulary (as measured
with the Shipley Vocabulary Test; Shipley, 1940), inhibition performance on the Go-No Go task (Donders, 1969), three components of attention: alerting, orienting, and executive control (as measured by the Attention Network Test [ANT]; Fan, McCandliss, Sommer, Raz, & Posner, 2002), and a taskswitching task (Kumada et al., 2005). For both the 1- and 3-year follow-up samples, there were minimal attrition effects, because the sample of participants who returned for the follow-up sessions (n = 33 at 1 year and n = 26 at 3 years) and those who opted not to return (n = 9 at 1 year and n = 15 at 3 years) did not differ in performance on most baseline cognitive measures or demographic variable data. The only significant difference was found in the 3-year follow-up sample. In particular, those who returned for the 3-year follow-up session scored significantly higher (suggesting better performance) on the orienting scale of the ANT (Fan et al., 2002) relative to those who opted not to return (see Table 1 for p value). Importantly, the ANT orienting score did not correlate with any Stroop ratio interference scores from any of the training sessions or the two follow-up sessions in the 3-year followup sample (Pearson’s r correlations ranged from −.232 to .292, ps > .14). This suggests that the orienting component of attention was not likely contributing to performance on the Stoop task. This baseline cognitive variable was thus not considered further in the final analyses. Training Gains and Maintenance The Stroop ratio interference score was calculated using the RT data from the standard block (Block 4, consistent with Wilkinson & Yang, 2012) at each session. Only RTs for correct responses were included. Following the same procedure as in Wilkinson and Yang (2012), RTs were trimmed such that any RT beyond 2.5 SDs from the mean for each trial type, at each follow-up session, and for each participant was excluded from the final analyses. As a result, 2.34% of the RTs were deleted. The original training gains and longterm maintenance of Stroop inhibition training benefits were examined using a Stroop RT ratio interference score (i.e., incongruent RT/neutral RT). Table 2 displays the raw RTs for each trial type separately for each follow-up sample across
Table 2. Mean Reaction Time (RT) for Each Trial Type Across All Training and Follow-Up Sessions Separately for the 1- and 3-Year Follow-Up Samples 1-Year follow-up (n = 33) Session 1 2 3 4 5 6 1-Year follow-up 3-Year follow-up
3-Year follow-up (n = 26)
Congruent
Incongruent
Neutral
Congruent
Incongruent
Neutral
888.20 (182.74) 840.35 (240.55) 843.41 (215.54) 801.07 (190.79) 795.97 (180.04) 786.31(212.08) 854.56 (214.89) —
1090.77 (331.23) 1009.48 (285.61) 988.17 (249.76) 947.77 (295.47) 899.70 (236.36) 931.95 (309.28) 977.61 (270.19) —
901.03 (188.94) 856.98 (197.11) 825.58 (174.74) 824.67 (241.93) 804.62 (175.09) 786.09 (197.01) 853.19 (208.44) —
873.97 (170.90) 815.59 (194.48) 815.26 (149.87) 776.58 (142.39) 771.51 (147.28) 760.59 (156.78) 829.77 (177.70) 836.28 (152.84)
1032.78 (241.28) 974.01 (248.02) 949.52 (171.26) 900.04 (230.05) 867.75 (208.26) 889.46 (258.59) 928.57 (189.13) 973.13 (199.00)
878.80 (175.40) 828.23 (159.76) 800.39 (120.66) 789.60 (148.56) 779.58 (135.85) 763.29 (146.34) 818.56 (148.07) 853.59 (138.14)
Note. Mean reaction times (in milliseconds) with standard deviations presented in parentheses. — = not applicable.
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
a single session of the Stroop task that was identical to the one administered at Session 1 of the original training study, except for the absence of the feedback manipulation at the two follow-up sessions. The specific follow-up version of the Stroop task involved one of the following two sets of colors: blue, orange, green, and pink (Set A), or pink, yellow, blue, and green (Set B). To minimize any item-specific effects, participants were assigned to the opposite color set at the 1-year follow-up session and the same color set at the 3-year follow-up session as the one designated at the original training Session 1. For example, if a participant completed color Set A (blue, orange, green, and pink) at the original training Session 1, they would be assigned to color Set B (pink, yellow, blue, and green) at the 1-year follow-up session and color Set A (blue, orange, green, and pink) at the 3-year follow-up session. The 1- and 3-year follow-up sessions were completed approximately 1 and 3 years after the original final training Session 6, with an average delay of 12.12 and 36.08 months, respectively. A 2-month time window was allowed for each follow-up session to accommodate any scheduling conflicts. All participants were compensated $10 for each hour of participation and debriefed at the end of each follow-up session.
LONG-TERM MAINTENANCE OF INHIBITION TRAINING
Page 5 of 8
Specifically, the long-term maintenance of Stroop inhibition training was evaluated by comparing performance at the two follow-up sessions to the final performance at Week 2 of the original training. No significant difference supports the presence of maintenance. In addition, we compared performance at the two follow-up sessions to baseline performance at Week 1 to assess whether performance at the two follow-up sessions was still above baseline level. The 1-year follow-up.—To evaluate the maintenance of the training benefits 1 year following the original training, the Stroop RT ratio interference scores for the 1-year followup sample (n = 33) were submitted to a repeated-measures ANOVA involving three sessions (Week 1, Week 2, and 1-year follow-up). The analysis revealed a significant session effect, F(2, 64) = 5.41, p = .007, η2 = .15 (see Figure 2). Planned paired t tests were conducted to compare performance at the 1-year follow-up with the final (Week 2) and baseline performance (Week 1) of original training. The 1-year follow-up performance (M = 1.14, SD = 0.09) did not significantly differ from Week 2 (M = 1.15, SD = 0.09), p = .97, d = 0.11. This supports the maintenance of the original training gains over a 1-year period. Furthermore, performance at the 1-year followup session was significantly better (i.e., smaller Stroop ratio interference) than Week 1 (M = 1.19, SD = 0.07), p = .012, d = 0.62, suggesting that inhibitory ability did not return back to baseline level 1 year after the original training. The 3-year follow-up.—For the 3-year follow-up sample (n = 26), the Stroop RT ratio interference scores were submitted to a repeated-measures ANOVA involving four sessions (Week 1, Week 2, 1-year follow-up, and 3-year follow-up). The session effect was marginally significant, F(3, 75) = 2.57, p = .060, η2 = .093 (see Figure 2). Planned t tests were conducted to compare performance at the two follow-up sessions (1 and 3 years) with the final (Week 2) and baseline performance (Week 1) of the original training. We also compared the ratio interference scores at the two follow-up sessions. Performance at both follow-up sessions (1 year: M = 1.13, SD = 0.08; 3 years: M = 1.14, SD = 0.10) did not significantly differ from Week 2 (M = 1.13, SD = 0.09), ps > .78
Figure 1. Mean reaction time (RT) Stroop ratio interference score (in milliseconds) separately for those who completed the 1-year follow-up session (n = 33) and those who completed the 3-year follow-up session (n = 26) across the original six training sessions. Error bars represent standard errors.
Figure 2. Mean reaction time (RT) Stroop interference ratio score (in milliseconds) in Week 1 and Week 2 of the original training and the two followup sessions separately for those who completed the 1-year follow-up session (n = 33) and those who completed the 3-year follow-up session (n = 26). Error bars represent standard errors.
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
all sessions. In addition, effect sizes (using Cohen’s d) were calculated based on a between-participants calculation (i.e., Cohen’s d = M1 − M2/SDpooled, where SDpooled = SQRT(SD12 + SD22)/2). This is a conservative approach for calculating effect size for within-group variables, because the high correlation between repeated-measures is not used to reduce the error term (Dunlap, Cortina, Vaslow, & Burke, 1996). Original training gain.—In order to re-examine the original training effects for both follow-up samples, Stroop RT ratio interference scores were submitted to a six-way (session) repeated-measures analysis of variance (ANOVA) separately for the 1-year follow-up sample (n = 33) and the 3-year follow-up sample (n = 26). We were specifically interested in the linear (suggesting incremental learning) and quadratic contrasts (suggesting saturation of learning) of the session effect for both groups. Critically, the linear, but not quadratic, session effect was significant for both the 1-year follow-up sample (n = 33), F(1, 32) = 6.02, p = .020, η2 = .16, and the 3-year follow-up sample (n = 26), F(1, 25) = 5.06, p = .034, η2 = .17 (see Figure 1). This confirms that both follow-up samples showed significant original training benefits. Visual inspection of the original training performance of the two follow-up samples (Figure 1) indicated that peak performance occurred at Session 5 (not the final Session 6). Additional analyses showed similar performance across the first 3 sessions (Week 1), by revealing no session effect for either the 1- or 3-year follow-up samples (ps > .19). Furthermore, the last three sessions (Week 2) showed consistently better performance than the average performance of Week 1 (ps = .001 for both samples). Therefore, to simplify the results and best capture the reliable training and maintenance effects, we calculated average performance across original training sessions 1–3 (Week 1) to index baseline performance and sessions 4–6 (Week 2) to index the final level of performance following original training. Long-term maintenance.—Given the sample size difference between the two follow-up sessions, the longterm maintenance of the training benefits were analyzed separately for the 1- and 3-year follow-up occasions.
Page 6 of 8
WILKINSON AND YANG
(ds ≤ 0.11). This replicates the finding of maintained training gains at the 1-year follow-up and further extends the maintenance to 3 years. In addition, performance at the two followup sessions was significantly better than baseline (Week 1; M = 1.18, SD = 0.09). This was evident at both the 1-year (p = .043, d = 0.59) and 3-year follow-up sessions (p = .047, d = 0.42). Finally, the comparison between the two follow-up sessions revealed equivalent performance, p = .90 (d = 0.11).
Funding This work was supported by grants from the Faculty of Arts Scholarly, Research and Creative Activity research fund of Ryerson University and the Natural Sciences and Engineering Research Council of Canada Discovery Grant (371762–2009) awarded to L. Yang. Acknowledgments The authors wish to thank all of the research assistants involved in recruitment and data collection. Conflict of Interest This work is based, in part, on the research conducted for the PhD dissertation of the first author, A. J. Wilkinson. A. J. Wilkinson is currently a postdoctoral fellow at the Bridgepoint Collaboratory for Research and Innovation in Toronto, Canada.
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
Discussion Long-term maintenance of training benefits in inhibition was assessed in healthy older adults at 1- and 3-year follow-up time points after a 2-week (3 sessions per week) Stroop training program. The current data support the maintenance of training gains at both follow-up sessions. In other words, the reduction in Stroop ratio interference (indexing better inhibition) achieved during the second week of a 2-week Stroop training program was well maintained at both the 1- and 3-year follow-up sessions. Furthermore, it was found that performance at the two follow-up sessions did not differ from each other, and both were better than baseline. Taken together, these results suggest that the original training-induced performance gains in inhibition are durable and can be maintained for 1 year and even 3 years in older adults. In addition, performance at the two follow-up sessions is maintained at a level beyond baseline performance. The current results demonstrate that older adults are able to maintain small-to-medium inhibition training gains (ds = 0.42–0.62) over 1- and 3-year periods (using Cohen’s index of effect size; Cohen, 1988, 1992). In line with previous research (e.g., Dahlin et al., 2008; Stigsdotter Neely & Bäckman, 1993), the current findings support the durability of training gains across a comparable follow-up period. In the existing body of literature, the durability of executive function training gains has been demonstrated for a shorter period of time—ranging from 3 months (e.g., Li et al., 2008) up to 18 months (e.g., Dahlin et al., 2008). This study adds to the literature by extending the maintenance of executive function training (using a Stroop task training program) to 3 years. Going beyond previous findings, the results of this study indicate that performance is well maintained and still above baseline level even over a period of 3 years following the original training. Our results, however, do not support the conclusions drawn by Kelly and colleagues (2014) based on a review of the cognitive training literature, which suggest that booster sessions (as well as adaptive training) may be required to show durability of training effects. In contrast, the current findings demonstrate effective maintenance even in the absence of booster sessions or an original adaptive training program. Future research would benefit from empirically testing these hypotheses. Although this follow-up study makes substantial contributions to the literature, three limitations should be noted.
First, due to the small sample size, it is possible that significant attrition effects may have gone undetected. However, it has been demonstrated in a recent study (Salthouse, 2014) that selection attrition does not necessarily predict differential magnitude of longitudinal change. Based on this finding, despite the possibility of insufficient power to detect selective attrition effects on certain variables in this study, we argue that the magnitude of long-term maintenance of the training effect on Stroop task performance is unlikely to change even if there had been no attrition (i.e., assuming all participants returned for both follow-up sessions). Second, the sample size at the 3-year follow-up session—in particular—was small (n = 26); however, we were restricted to the number of participants who were willing to return for testing. Nevertheless, the sample size of the 3-year follow-up group still reflects a return rate of 61.9% from the original training group (n = 42). This retention rate is comparable with that of a follow-up study of similar duration (i.e., 3.5 years; Stigsdotter Neely & Bäckman, 1993). The third limitation is with respect to the generalizability of results. The study sample consisted of a group of healthy, well-educated, and high functioning older adults, which may not be representative of the typical older adult population. Given this, generalizability of the current findings may be limited. Regardless of these limitations, this study makes novel contributions to the literature by demonstrating that healthy older adults are able to maintain inhibition training gains for up to 3 years following the original training. Benefits in inhibitory processing, such as withholding an automatic but inappropriate response, can help to improve the daily lives of older adults. For example, if a doctor suddenly advises an individual to stop taking a certain medication that was previously taken regularly (e.g., every morning), efficient inhibition could help to minimize accidental ingestion, which may impact overall health and well-being. In conclusion, the current follow-up study adds to the literature by demonstrating long-term maintenance of training effects in inhibition above baseline levels 1 and 3 years following original training. Remarkably, this effect was shown using a single session of the Stroop task at each follow-up and without any booster sessions before the follow-up testing.
LONG-TERM MAINTENANCE OF INHIBITION TRAINING
Correspondence Correspondence should be addressed to Andrea J. Wilkinson, PhD, Department of Psychology, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada. E-mail: [email protected].
Gazzaley, A., Cooney, J. W., Rissman, J., & D’Esposito, M. (2005). Topdown suppression deficit underlies working memory impairment in normal aging. Nature Neuroscience, 8, 1298–1300. doi:10.1038/ nn1543 Gross, A. L., Rebok, G. W., Unverzagt, F. W., Willis, S. L., & Brandt, J. (2011). Cognitive predictors of everyday functioning in older adults: Results from the ACTIVE Cognitive Intervention Trial. The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 66, 557–566. doi:10.1093/geronb/gbr033 Günther, V. K., Schäfer, P., Holzner, B. J., & Kemmler, G. W. (2003). Long-term improvements in cognitive performance through computer-assisted cognitive training: A pilot study in a residential home for older people. Aging & Mental Health, 7, 200–206. doi:10.1080/1360786031000101175 Hamm, V. P., & Hasher, L. (1992). Age and the availability of inferences. Psychology and Aging, 7, 56–64. doi:10.1037/0882-7974.7.1.56 Harnishfeger, K. K. (1995). The development of cognitive inhibition: Theories, definitions, and research evidence. In F. N. Dempster & C. J. Brainerd (Eds.), Interference and inhibition in cognition (pp. 175–204). San Diego, CA: Academic Press. doi:10.1016/ B978-012208930-5/50007-6 Hasher, L., Lustig, C., & Zacks, R. (2007). Inhibitory mechanisms and the control of attention. In A. R. A. Conway, C. Jarrold, M. J., Kane, A. Miyake & J. N. Towse (Eds.), Variation in working memory (pp. 227–249). New York, NY: Oxford University Press. Hasher, L., Zacks, R. T., & May, C. P. (1999). Inhibitory control, circadian arousal, and age. In D. Gopher & A. Koriat (Eds.), Attention and performance XVII: Cognitive regulation of performance: Interaction of theory and application (pp. 653–675). Cambridge, MA: The MIT Press. Katzman, R., Brown, T., Fuld, P., Peck, A., Schechter, R., & Schimmel, H. (1983). Validation of a short Orientation-Memory-Concentration Test of cognitive impairment. The American Journal of Psychiatry, 140, 734–739. Kelly, M. E., Loughrey, D., Lawlor, B. A., Robertson, I. H., Walsh, C., & Brennan, S. (2014). The impact of cognitive training and mental stimulation on cognitive and everyday functioning of healthy older adults: A systematic review and meta-analysis. Ageing Research Reviews, 15, 28–43. doi:10.1016/j.arr.2014.02.004 Kramer, A. F., Hahn, S., & Gopher, D. (1999). Task coordination and aging: Explorations of executive control processes in the task switching paradigm. Acta Psychologica, 101, 339–378. doi:10.1016/ S0001-6918(99)00011-6 Kumada, T., Kitajima, M., Ogi, H., Akamatu, M., Tahira, H., & Yamazaki, H. (2005). The development of cognitive aging test for usability test: Focusing of attention and executive function for older adults [Japanese Abstract]. Proceedings of the Japanese Society for Cognitive Psychology, 3rd Meeting, 24. Kyoto, Japan: Japan Science and Technology Information Aggregator, Electronic (J-STAGE). Li, S. C., Schmiedek, F., Huxhold, O., Röcke, C., Smith, J., & Lindenberger, U. (2008). Working memory plasticity in old age: Practice gain, transfer, and maintenance. Psychology and Aging, 23, 731–742. doi:10.1037/a0014343 Logan, G. D. (1994). On the ability to inhibit thought and action: A user’s guide to the stop signal paradigm. In D. Dagenbach & T. H. Carr (Eds.), Inhibitory processes in attention, memory, and language (pp. 189–239). San Diego, CA: Academic Press, Inc. Nieuwenhuis, S., Ridderinkhof, K. R., de Jong, R., Kok, A., & van der Molen, M. W. (2000). Inhibitory inefficiency and failures of intention activation: Age-related decline in the control of saccadic eye movements. Psychology and Aging, 15, 635–647. doi:10.1037/0882-7974.15.4.635 Rebok, G. W., Ball, K., Guey, L. T., Jones, R. N., Kim, H.-Y., King, J. W., . . ., Willis, S. L. (2014). Ten-year effects of the Advanced Cognitive Training for Independent and Vital Elderly Cognitive Training trial
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
References Ball, K., Berch, D. B., Helmers, K. F., Jobe, J. B., Leveck, M. D., Marsiske, M.,…Willis, S. L. (2002). Effects of cognitive training interventions with older adults: A randomized controlled trial. The Journal of the American Medical Association, 288, 2271–2281. doi:10.1001/ jama.288.18.2271 Baltes, P. B., & Lindenberger, U. (1988). On the range of cognitive plasticity in old age as a function of experience: 15 years of intervention research. Behavior Therapy, 19, 283–300. doi:10.1016/ S0005-7894(88)80003-0 Beck, A. T., Epstein, N., Brown, G., & Steer, R. A. (1988). An inventory for measuring clinical anxiety: Psychometric properties. Journal of Consulting and Clinical Psychology, 56, 893–897. doi:10.1037/0022-006X.56.6.893 Biss, R. K., Campbell, K. L., & Hasher, L. (2013). Interference from previous distraction disrupts older adults’ memory. The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 68, 558–561. doi:10.1093/geronb/gbs074 Bojko, A., Kramer, A. F., & Peterson, M. S. (2004). Age equivalence in switch costs for prosaccade and antisaccade tasks. Psychology and Aging, 19, 226–234. doi:10.1037/0882-7974.19.1.226 Borella, E., Carretti, B., Riboldi, F., & De Beni, R. (2010). Working memory training in older adults: Evidence of transfer and maintenance effects. Psychology and Aging, 25, 767–778. doi:10.1037/a0020683 Brehmer, Y., Westerberg, H., & Bäckman, L. (2012). Working-memory training in younger and older adults: Training gains, transfer, and maintenance. Frontiers in Human Neuroscience, 6, 63. doi:10.3389/ fnhum.2012.00063 Butler, K. M., & Zacks, R. T. (2006). Age deficits in the control of prepotent responses: Evidence for an inhibitory decline. Psychology and Aging, 21, 638–643. doi:10.1037/0882-7974.21.3.638 Cohen, J. (1988). Statistical power analysis for the behavioral sciences (2nd ed.). Hillsdale, NJ: Lawrence Erlbaum Associates, Inc. Cohen, J. (1992). A power primer. Psychological Bulletin, 112, 155–159. doi:10.1037/0033-2909.112.1.155 Dahlin, E., Nyberg, L., Bäckman, L., & Neely, A. S. (2008). Plasticity of executive functioning in young and older adults: Immediate training gains, transfer, and long-term maintenance. Psychology and Aging, 23, 720–730. doi:10.1037/a0014296 Davidson, D. J., Zacks, R. T., & Williams, C. C. (2003). Stroop interference, practice, and aging. Neuropsychology, Development, and Cognition, 10, 85–98. doi:10.1076/anec.10.2.85.14463 Donders, F. C. (1969). On the speed of mental processes. In W. G. Koster (Ed.), Attention and performance II (pp. 412–431). Amsterdam, The Netherlands: North-Holland Publishing Co. (Original work published in 1868). Dulaney, C. L., & Rogers, W. A. (1994). Mechanisms underlying reduction in Stroop interference with practice for young and old adults. Journal of Experimental Psychology, 20, 470–484. doi:10.1037/0278-7393.20.2.470 Dunlap, W. P., Cortina, J. M., Vaslow, J. B., & Burke, M. J. (1996). Meta-analysis of experiments with matched groups or repeated measures designs. Psychological Methods, 1, 170–177. doi:10.1037/1082-989X.1.2.170 Dvorine, I. (1953). Dvorine pseudo-isochromatic plates [Apparatus] (2nd ed.). Baltimore, MD: Harcourt, Brace & World, Inc. Fan, J., McCandliss, B. D., Sommer, T., Raz, A., & Posner, M. I. (2002). Testing the efficiency and independence of attentional networks. Journal of Cognitive Neuroscience, 14, 340–347. doi:10.1162/089892902317361886
Page 7 of 8
Page 8 of 8
WILKINSON AND YANG
Verhaeghen, P. (2011). Aging and executive control: Reports of a demise greatly exaggerated. Current Directions in Psychological Science, 20, 174–180. doi:10.1177/0963721411408772 Wilkinson, A. J., & Yang, L. (2012). Plasticity of inhibition in older adults: Retest practice and transfer effects. Psychology and Aging, 27, 606– 615. doi:10.1037/a0025926 Willis, S. L., & Nesselroade, C. S. (1990). Long-term effects of fluid ability training in old-old age. Developmental Psychology, 26, 905–910. doi:10.1037/0012-1649.26.6.905 Willis, S. L., Tennstedt, S. L., Marsiske, M., Ball, K., Elias, J., Koepke, K. M.,…Wright, E. (2006). Long-term effects of cognitive training on everyday functional outcomes in older adults. Journal of American Medical Association, 296, 2805–2814. doi:10.1001/ jama.296.23.2805 Yang, L., & Hasher, L. (2007). The enhanced effects of pictorial distraction in older adults. The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 62, P230–P233. doi:10.1093/ geronb/62.4.P230 Yang, L., & Krampe, R. T. (2009). Long-term maintenance of retest learning in young old and oldest old adults. The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 64, 608–611. doi:10.1093/geronb/gbp063
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
on cognition and everyday functioning in older adults. Journal of the American Geriatrics Society, 62, 16–24. doi:10.1111/jgs.12607 Rosenbaum, J. G. (1976). Rosenbaum Pocket Vision Screener [Apparatus]. Cleveland, OH: Design courtesy of J. G. Rosenbaum, M. D. Rowe, G., Valderrama, S., Hasher, L., & Lenartowicz, A. (2006). Attentional dysregulation: A benefit for implicit memory. Psychology and Aging, 21, 826–830. doi:10.1037/0882-7974.21.4.826 Salthouse, T. A. (2014). Selectivity of attrition in longitudinal studies of cognitive functioning. The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 69, 567–574. doi:10.1093/geronb/gbt046 Schwartz, K., & Verhaeghen, P. (2008). ADHD and Stroop interference from age 9 to age 41 years: A meta-analysis of developmental effects. Psychological Medicine, 38, 1607–1616. doi:10.1017/S003329170700267X Shipley, W. C. (1940). A self-administering scale for measuring intellectual impairment and deterioration. Journal of Psychology, 9, 371– 377. doi:10.1080/00223980.1940.9917704 Stigsdotter Neely, A. S., & Bäckman, L. (1993). Long-term maintenance of gains from memory training in older adults: Two 3 ½-year follow-up studies. Journal of Gerontology, 48, P233–P237. doi:10.1093/geronj/48.5.P233 Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18, 643–662. doi:10.1037/h0054651
Long-Term Maintenance of Inhibition Training Effects in Older Adults: 1- and 3-Year Follow-Up Andrea J. Wilkinson and Lixia Yang Department of Psychology, Ryerson University, Toronto, Ontario, Canada.
Methods. Participants from an original 6-session Stroop training study (Wilkinson & Yang, 2012 [Wilkinson, A. J., & Yang, L. (2012). Plasticity of inhibition in older adults: Retest practice and transfer effects. Psychology and Aging, 27, 606–615. doi:10.1037/a0025926]) were invited to come back to the lab to complete a single session of the Stroop task at 2 different time points. Thirty-three older adults returned for the 1-year follow-up session, and 26 of them returned for the 3-year follow-up session. Results. The results revealed maintenance of the training-induced inhibition gains at both follow-up sessions. Furthermore, performance at the 2 follow-up sessions was better (i.e., reduced Stroop ratio interference score) than baseline level. Discussion. The findings demonstrate the durability of inhibition training gains in older adults for up to a 3-year period. These results further extend the literature on long-term maintenance of cognitive training benefits in older adults by examining the durability of training effects in inhibition, an important executive function, and by covering a substantial maintenance period (i.e., up to 3 years). Key Words: Aging—Durability—Executive function—Inhibition—Long-term maintenance.
Background The evaluation of long-term maintenance following cognitive training is important because it demonstrates endurance of the learning induced by the initial training. Previous literature has shown that older adults are able to maintain cognitive training effects for long periods of time, ranging from several months (e.g., Borella, Carretti, Riboldi, & De Beni, 2010; Brehmer, Westerberg, & Bäckman, 2012; Dahlin, Nyberg, Bäckman, & Neely, 2008; Günther, Schäfer, Holzner, & Kemmler, 2003; Kramer, Hahn, & Gopher, 1999; Li et al., 2008; Yang & Krampe, 2009) all the way up to several years (Ball et al., 2002; Rebok et al., 2014; Stigsdotter Neely & Bäckman, 1993; Willis & Nesselroade, 1990; Willis et al., 2006). For example, in the Advanced Cognitive Training for Independent and Vital Elderly study, training gains in reasoning and speed of processing, but not memory, were demonstrated to be maintained at or above baseline level 10 years after original training, with the inclusion of booster sessions at, approximately, 1 and 3 years (Rebok et al., 2014). In a recent systematic review and meta-analysis (Kelly et al., 2014), it was suggested that booster sessions (as well as an adaptive training protocol) could enhance the maintenance of training effects. However, not all cognitive training follow-up studies include booster sessions (e.g., Borella et al., 2010; Brehmer et al., 2012; Dahlin et al., 2008; Li et al., 2008; Stigsdotter Neely & Bäckman, 1993). For example, following memory
training, older adults were able to maintain the performance gain over baseline level for 3.5 years—in the absence of any booster training sessions (Stigsdotter Neely & Bäckman, 1993). So, the benefit of booster sessions is still debated in the literature. In this study, we examined the longitudinal benefits of inhibition training without any booster sessions. The durability of training gains in older adults has been demonstrated in a variety of cognitive domains, including memory, reasoning, perceptual-motor speed, and visual attention (Günther et al., 2003; Rebok et al., 2014; Stigsdotter Neely & Bäckman, 1993; Willis & Nesselroade, 1990; Willis et al., 2006; Yang & Krampe, 2009). It has also been shown in training with executive functions, such as updating (Dahlin et al., 2008; Li et al., 2008). However, to our knowledge, little has been done to examine the longterm maintenance of training gains in inhibition, one type of executive function, among older adults. This study serves to fill this gap. Examining the durability of executive function training is important, especially among older adults, because executive functions have been identified as critical for the effective completion of activities of daily living (Gross, Rebok, Unverzagt, Willis, & Brandt, 2011). Inhibition, in particular, is an executive ability that functions to regulate attention and keep cognitive processing in line with task goals (Harnishfeger, 1995; Hasher, Zacks, & May, 1999; Logan, 1994). A considerable amount of literature has
© The Author 2015. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: [email protected]. Received May 12, 2014; Accepted December 3, 2014 Decision Editor: Myra Fernandes, PhD
Page 1 of 8
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
Objectives. The aim of this study is to examine the long-term maintenance of training benefits in inhibition, as measured with the Stroop task, in older adults over 1- and 3-year periods.
Page 2 of 8
WILKINSON AND YANG
the remaining received individualized and adaptive feedback based on their performance on previous trials at the end of each trial (for additional details, see Wilkinson & Yang, 2012). Finally, the standard Block 4 followed the same trial procedure, but without any feedback in order to provide a fair comparison across the feedback groups in the analysis of training benefits. The results demonstrated improvements in inhibition, as indexed by reduced Stroop interference scores (i.e., difference scores calculated between incongruent and neutral trials), across the six training sessions. Interestingly, this effect was equivalent across all three feedback groups, suggesting that the type and amount of externally generated feedback did not modulate the magnitude of training-induced improvements in inhibition. As a long-term maintenance follow-up, this study tested returning participants from the original study by Wilkinson and Yang (2012) at 1 and 3 years following the original training. In an effort to control for general slowing with aging in the Stroop interference effect, we followed the approach used in some recent meta-analyses (Schwartz & Verhaeghen, 2008; Verhaeghen, 2011) and calculated a Stroop ratio interference score by dividing the RT of incongruent trials by that of the neutral trials (incongruent RT/neutral RT). The ratio score indexes the cost of responding to the executive control (incongruent) condition as a proportion of baseline speed in color naming (neutral condition). This score controls for agerelated changes in general processing speed (Schwartz & Verhaeghen, 2008; Verhaeghen, 2011), and thus provides a more accurate measure of inhibitory efficiency relative to a simple difference score (incongruent RT – neutral RT). In this study, we first used the ratio score to re-examine the original training effects in Wilkinson and Yang (2012), then we used it to evaluate maintenance of the training gains over 1- and 3-year periods. This allowed us to assess training-induced performance changes that were specific to interference, while taking fluctuations in response speed across sessions into consideration. In light of previous long-term maintenance training studies that cover comparable duration periods (e.g., 18 months in Dahlin et al., 2008; and 3.5 years in Stigsdotter Neely & Bäckman, 1993), we expect that the original training gain will be maintained at both follow-up sessions, where performance will continue to exceed baseline performance level. Method Participants The original training sample in Wilkinson and Yang (2012) consisted of 42 older adults (28 women, age range = 60–84 years; mean [M] = 70.98, standard deviation [SD] = 6.42) recruited from the internal Ryerson Senior Participant Pool. Given the lack of feedback
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
consistently shown age-related deficits in inhibition (Biss, Campbell, & Hasher, 2013; Bojko, Kramer, & Peterson, 2004; Butler & Zacks, 2006; Gazzaley, Cooney, Rissman, & D’Esposito, 2005; Hamm & Hasher, 1992; Hasher et al., 1999; Hasher, Lustig, & Zacks, 2007; Nieuwenhuis, Ridderinkhof, de Jong, Kok, & van der Molen, 2000; Rowe, Valderrama, Hasher, & Lenartowicz, 2006; Yang & Hasher, 2007). In literature, one commonly used inhibition measure is the Stroop task. In a typical Stroop task, participants are instructed to name the ink color in which a color word is printed (e.g., RED printed in blue ink, respond blue). There are three types of Stroop stimuli: congruent (e.g., “GREEN” in green ink, respond green), incongruent (e.g., “GREEN” in blue ink, respond blue), and neutral (e.g., “XXXXX” in green ink, respond green; Wilkinson & Yang, 2012—adapted from Stroop [1935]). On incongruent trials, there is a conflict between the color word and ink color of the stimulus; therefore, participants must suppress the automatic word reading response in order to correctly identify the ink color of the stimulus. Encouragingly, some previous work has demonstrated plasticity, defined as training-induced improvement (Baltes & Lindenberger, 1988), of inhibition among older adults using the Stroop task within a single session or across two sessions (e.g., Davidson, Zacks, & Williams, 2003; Dulaney & Rogers, 1994). Going beyond the literature, Wilkinson and Yang (2012) demonstrated sizable plasticity of inhibition, after controlling for item-specific effects, across six training sessions among older adults. This study serves as a follow up to Wilkinson and Yang (2012), aiming to assess the long-term maintenance of the inhibition training effects across 1- and 3-year periods. In the original work by Wilkinson and Yang (2012), 42 healthy older adults (aged 60–84), evenly divided into three feedback groups, completed a 2-week training program on the Stroop task. Each week involved three training sessions. At each session, participants completed four blocks of Stroop task trials (i.e., key-color acquisition, practice, training, and standard). The purpose of the keycolor acquisition block was to familiarize participants with the mapping scheme between the response keys and colors. During this block, participants received accuracy feedback after each trial. The purpose of practice Block 2 was to familiarize participants with the trial procedure of the upcoming training Block 3. In this way, only those participants in the individualized and adaptive feedback group received the corresponding feedback, whereas other participants did not receive any feedback at all. The training Block 3 followed the same procedure as practice Block 2 except that participants received the full manipulation of feedback, such that some participants did not receive any feedback (i.e., no-feedback control), some others received summary feedback on the average reaction time (RT) and accuracy at the end of the block, and
Page 3 of 8
LONG-TERM MAINTENANCE OF INHIBITION TRAINING
all other participants (98.5%) at the 3-year follow-up session. Therefore, this participant was included in the final analyses. Materials and Procedure At each follow-up session, a similar trial procedure as the one implemented in Wilkinson and Yang (2012) was adopted; however, participants were not trained (i.e., they did not receive any feedback on performance in any of the blocks). In particular, participants completed four blocks of the Stroop task: key-color acquisition (Block 1: 40 trials); practice (Block 2: 24 trials); training (Block 3: 216 trials); and standard (Block 4: 144 trials). Blocks 1 and 2 followed the same trial procedure, except that accuracy feedback was provided in Block 1, but not in Block 2. The training Block 3 and standard Block 4 were named as such for consistency with the terminology used in the original study by Wilkinson and Yang (2012). Critically, and different from the original study in which feedback was manipulated during the training Block 3, no feedback was provided for any of the participants in this block at the two follow-up sessions. As a result, Blocks 3 and 4 followed the same trial procedure, both without feedback, at the two follow-up sessions. In the original study, there were two counterbalance conditions in which the set of colors used for the Stroop task varied across sessions. This was done to minimize item-specific effects (for additional details, see Wilkinson & Yang, 2012). At both follow-up sessions, participants completed
Table 1. Returned Versus Not Returned Participant Demographic Characteristics and Baseline Cognitive Performance Assessed at Pretest 1-Year follow-up Characteristic Age (years) Gender (women, n)a Education (years) Health Visual acuity Short blessed test BAI Shipley Go-No Go Digit symbol Letter series ANT Alerting Orienting Exec control Task-switching task
3-Year follow-up
Returned (n = 33)
Not returned (n = 9)
d
Returned (n = 26)
Not returned (n = 15)
71.12 (6.52) 21 16.27 (3.44) 8.48 (0.97) 31.52 (8.61) 1.06 (1.62) 6.88 (6.39) 36.70 (3.27) 6.52 (3.81) 61.52 (12.85) 9.67 (4.42)
70.44 (6.39) 7 15.11 (4.76) 8.61 (1.11) 36.11 (15.16) .44 (1.33) 7.11 (5.95) 34.67 (5.41) 7.11 (6.41) 54.56 (11.84) 8.44 (4.28)
.78 .43 .42 .74 .24 .30 .92 .16 .72 .15 .46
p Value
0.11 — 0.28 0.12 0.37 0.42 0.04 0.45 0.11 0.56 0.28
69.81 (5.91) 16 16.34 (3.52) 8.58 (0.95) 31.35 (9.33) .96 (1.46) 7.31 (6.72) 36.31 (3.40) 5.85 (3.26) 62.15 (11.28) 10.12 (4.35)
72.60 (7.10) 11 15.40 (4.22) 8.50 (1.05) 34.67 (12.17) .93 (1.83) 6.53 (5.60) 36.00 (4.69) 8.07 (5.87) 55.53 (14.64) 8.27 (4.43)
.18 .44 .45 .81 .33 .96 .71 .81 .13 .11 .20
p Value
0.43 — 0.24 0.08 0.31 0.02 0.13 0.08 0.47 0.51 0.42
28.32 (42.41) 81.53 (42.60) 114.66 (50.68) 16.76 (236.86)
31.97 (30.70) 55.02 (27.71) 95.91 (71.21) 39.93 (115.14)
.81 .08 .37 .78
0.10 0.74 0.30 0.12
34.07 (38.61) 86.47 (41.78) 111.80 (48.13) 38.56 (179.63)
26.78 (36.13) 54.19 (28.92) 99.72 (58.37) .18 (276.59)
.56 .01* .48 .59
0.19 0.90 0.23 0.16
d
Notes. BAI = Beck’s Anxiety Inventory; Shipley = Shipley Vocabulary Test; ANT = Attention Network Test (alerting, orienting, exec control = executive control). Mean scores with standard deviations presented in parentheses for each cell (except for gender). Education was indexed by the average number of years of formal education; health was indexed by a self-report score out of 10; visual acuity was indexed by the near visual acuity score from the Rosenbaum Visual Acuity Pocket Screener (score 20/—); digit symbol, letter series, and Shipley were scored by the average number of correct solutions; average scores were displayed for BAI and short blessed test; Go-No Go was scored by the average number of false alarms; ANT (alerting, orienting, and executive control) and the task-switching task were scored by a difference reaction time score in milliseconds. — = not applicable; d = Cohen’s d effect size calculation for between subjects. p Values are from independent t tests comparing “Returned” to “Not returned” at each follow-up session. a Denotes the use of chi-square statistics. *p < .05.
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
effects in the original training study, as well as the small sample size per feedback group at each follow-up session, the data presented were collapsed across feedback conditions. The 1-year follow-up sample.—Thirty-three of the 42 participants from the original sample returned for the 1-year follow-up session (21 women, age range = 60–84 years, M = 71.12, SD = 6.52). Table 1 displays details of the demographic information and baseline cognitive performance collected at the pretest session of the original training study. The detailed analysis and results on the attrition effects are presented in the Results section. The 3-year follow-up sample.—One participant was accidentally tested 2 years after the original training. This individual was excluded from the final analyses reported below. Twenty-six of the 33 participants who were tested at the 1-year follow-up session returned for the 3-year follow-up session (16 women, age range = 60–80 years, M = 69.81, SD = 5.91). The attrition effects were analyzed in the same way as for the 1-year follow-up sample (see the Results section for details). At the 3-year follow-up session, color blindness was assessed using the Dvorine Pseudo-Isochromatic Plates (Dvorine 1953). One participant was suspected for possible color blindness, as indicated by difficulty in answering five items on the Dvorine Pseudo-Isochromatic Plates test. This individual, however, showed a similar and acceptable average accuracy score (90.3%) on the Stroop task, compared with
Page 4 of 8
WILKINSON AND YANG
Results All statistical analyses were conducted using SPSS 20. Attrition Effects To determine the selective attrition effects, we compared participants who returned for the follow-up sessions and those who opted not to return on baseline cognitive measures and demographic variables using independent t tests (see Table 1). The following outcome variables were involved in these analyses: age, gender, years of education, self-reported health rating, visual acuity (as measured with the Rosenbaum Pocket Vision Screener; Rosenbaum, 1976), cognitive impairment (as assessed with the Short Blessed Test; Katzman et al., 1983), anxiety (as measured with the Beck Anxiety Inventory; Beck, Epstein, Brown, & Steer, 1988), vocabulary (as measured
with the Shipley Vocabulary Test; Shipley, 1940), inhibition performance on the Go-No Go task (Donders, 1969), three components of attention: alerting, orienting, and executive control (as measured by the Attention Network Test [ANT]; Fan, McCandliss, Sommer, Raz, & Posner, 2002), and a taskswitching task (Kumada et al., 2005). For both the 1- and 3-year follow-up samples, there were minimal attrition effects, because the sample of participants who returned for the follow-up sessions (n = 33 at 1 year and n = 26 at 3 years) and those who opted not to return (n = 9 at 1 year and n = 15 at 3 years) did not differ in performance on most baseline cognitive measures or demographic variable data. The only significant difference was found in the 3-year follow-up sample. In particular, those who returned for the 3-year follow-up session scored significantly higher (suggesting better performance) on the orienting scale of the ANT (Fan et al., 2002) relative to those who opted not to return (see Table 1 for p value). Importantly, the ANT orienting score did not correlate with any Stroop ratio interference scores from any of the training sessions or the two follow-up sessions in the 3-year followup sample (Pearson’s r correlations ranged from −.232 to .292, ps > .14). This suggests that the orienting component of attention was not likely contributing to performance on the Stoop task. This baseline cognitive variable was thus not considered further in the final analyses. Training Gains and Maintenance The Stroop ratio interference score was calculated using the RT data from the standard block (Block 4, consistent with Wilkinson & Yang, 2012) at each session. Only RTs for correct responses were included. Following the same procedure as in Wilkinson and Yang (2012), RTs were trimmed such that any RT beyond 2.5 SDs from the mean for each trial type, at each follow-up session, and for each participant was excluded from the final analyses. As a result, 2.34% of the RTs were deleted. The original training gains and longterm maintenance of Stroop inhibition training benefits were examined using a Stroop RT ratio interference score (i.e., incongruent RT/neutral RT). Table 2 displays the raw RTs for each trial type separately for each follow-up sample across
Table 2. Mean Reaction Time (RT) for Each Trial Type Across All Training and Follow-Up Sessions Separately for the 1- and 3-Year Follow-Up Samples 1-Year follow-up (n = 33) Session 1 2 3 4 5 6 1-Year follow-up 3-Year follow-up
3-Year follow-up (n = 26)
Congruent
Incongruent
Neutral
Congruent
Incongruent
Neutral
888.20 (182.74) 840.35 (240.55) 843.41 (215.54) 801.07 (190.79) 795.97 (180.04) 786.31(212.08) 854.56 (214.89) —
1090.77 (331.23) 1009.48 (285.61) 988.17 (249.76) 947.77 (295.47) 899.70 (236.36) 931.95 (309.28) 977.61 (270.19) —
901.03 (188.94) 856.98 (197.11) 825.58 (174.74) 824.67 (241.93) 804.62 (175.09) 786.09 (197.01) 853.19 (208.44) —
873.97 (170.90) 815.59 (194.48) 815.26 (149.87) 776.58 (142.39) 771.51 (147.28) 760.59 (156.78) 829.77 (177.70) 836.28 (152.84)
1032.78 (241.28) 974.01 (248.02) 949.52 (171.26) 900.04 (230.05) 867.75 (208.26) 889.46 (258.59) 928.57 (189.13) 973.13 (199.00)
878.80 (175.40) 828.23 (159.76) 800.39 (120.66) 789.60 (148.56) 779.58 (135.85) 763.29 (146.34) 818.56 (148.07) 853.59 (138.14)
Note. Mean reaction times (in milliseconds) with standard deviations presented in parentheses. — = not applicable.
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
a single session of the Stroop task that was identical to the one administered at Session 1 of the original training study, except for the absence of the feedback manipulation at the two follow-up sessions. The specific follow-up version of the Stroop task involved one of the following two sets of colors: blue, orange, green, and pink (Set A), or pink, yellow, blue, and green (Set B). To minimize any item-specific effects, participants were assigned to the opposite color set at the 1-year follow-up session and the same color set at the 3-year follow-up session as the one designated at the original training Session 1. For example, if a participant completed color Set A (blue, orange, green, and pink) at the original training Session 1, they would be assigned to color Set B (pink, yellow, blue, and green) at the 1-year follow-up session and color Set A (blue, orange, green, and pink) at the 3-year follow-up session. The 1- and 3-year follow-up sessions were completed approximately 1 and 3 years after the original final training Session 6, with an average delay of 12.12 and 36.08 months, respectively. A 2-month time window was allowed for each follow-up session to accommodate any scheduling conflicts. All participants were compensated $10 for each hour of participation and debriefed at the end of each follow-up session.
LONG-TERM MAINTENANCE OF INHIBITION TRAINING
Page 5 of 8
Specifically, the long-term maintenance of Stroop inhibition training was evaluated by comparing performance at the two follow-up sessions to the final performance at Week 2 of the original training. No significant difference supports the presence of maintenance. In addition, we compared performance at the two follow-up sessions to baseline performance at Week 1 to assess whether performance at the two follow-up sessions was still above baseline level. The 1-year follow-up.—To evaluate the maintenance of the training benefits 1 year following the original training, the Stroop RT ratio interference scores for the 1-year followup sample (n = 33) were submitted to a repeated-measures ANOVA involving three sessions (Week 1, Week 2, and 1-year follow-up). The analysis revealed a significant session effect, F(2, 64) = 5.41, p = .007, η2 = .15 (see Figure 2). Planned paired t tests were conducted to compare performance at the 1-year follow-up with the final (Week 2) and baseline performance (Week 1) of original training. The 1-year follow-up performance (M = 1.14, SD = 0.09) did not significantly differ from Week 2 (M = 1.15, SD = 0.09), p = .97, d = 0.11. This supports the maintenance of the original training gains over a 1-year period. Furthermore, performance at the 1-year followup session was significantly better (i.e., smaller Stroop ratio interference) than Week 1 (M = 1.19, SD = 0.07), p = .012, d = 0.62, suggesting that inhibitory ability did not return back to baseline level 1 year after the original training. The 3-year follow-up.—For the 3-year follow-up sample (n = 26), the Stroop RT ratio interference scores were submitted to a repeated-measures ANOVA involving four sessions (Week 1, Week 2, 1-year follow-up, and 3-year follow-up). The session effect was marginally significant, F(3, 75) = 2.57, p = .060, η2 = .093 (see Figure 2). Planned t tests were conducted to compare performance at the two follow-up sessions (1 and 3 years) with the final (Week 2) and baseline performance (Week 1) of the original training. We also compared the ratio interference scores at the two follow-up sessions. Performance at both follow-up sessions (1 year: M = 1.13, SD = 0.08; 3 years: M = 1.14, SD = 0.10) did not significantly differ from Week 2 (M = 1.13, SD = 0.09), ps > .78
Figure 1. Mean reaction time (RT) Stroop ratio interference score (in milliseconds) separately for those who completed the 1-year follow-up session (n = 33) and those who completed the 3-year follow-up session (n = 26) across the original six training sessions. Error bars represent standard errors.
Figure 2. Mean reaction time (RT) Stroop interference ratio score (in milliseconds) in Week 1 and Week 2 of the original training and the two followup sessions separately for those who completed the 1-year follow-up session (n = 33) and those who completed the 3-year follow-up session (n = 26). Error bars represent standard errors.
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
all sessions. In addition, effect sizes (using Cohen’s d) were calculated based on a between-participants calculation (i.e., Cohen’s d = M1 − M2/SDpooled, where SDpooled = SQRT(SD12 + SD22)/2). This is a conservative approach for calculating effect size for within-group variables, because the high correlation between repeated-measures is not used to reduce the error term (Dunlap, Cortina, Vaslow, & Burke, 1996). Original training gain.—In order to re-examine the original training effects for both follow-up samples, Stroop RT ratio interference scores were submitted to a six-way (session) repeated-measures analysis of variance (ANOVA) separately for the 1-year follow-up sample (n = 33) and the 3-year follow-up sample (n = 26). We were specifically interested in the linear (suggesting incremental learning) and quadratic contrasts (suggesting saturation of learning) of the session effect for both groups. Critically, the linear, but not quadratic, session effect was significant for both the 1-year follow-up sample (n = 33), F(1, 32) = 6.02, p = .020, η2 = .16, and the 3-year follow-up sample (n = 26), F(1, 25) = 5.06, p = .034, η2 = .17 (see Figure 1). This confirms that both follow-up samples showed significant original training benefits. Visual inspection of the original training performance of the two follow-up samples (Figure 1) indicated that peak performance occurred at Session 5 (not the final Session 6). Additional analyses showed similar performance across the first 3 sessions (Week 1), by revealing no session effect for either the 1- or 3-year follow-up samples (ps > .19). Furthermore, the last three sessions (Week 2) showed consistently better performance than the average performance of Week 1 (ps = .001 for both samples). Therefore, to simplify the results and best capture the reliable training and maintenance effects, we calculated average performance across original training sessions 1–3 (Week 1) to index baseline performance and sessions 4–6 (Week 2) to index the final level of performance following original training. Long-term maintenance.—Given the sample size difference between the two follow-up sessions, the longterm maintenance of the training benefits were analyzed separately for the 1- and 3-year follow-up occasions.
Page 6 of 8
WILKINSON AND YANG
(ds ≤ 0.11). This replicates the finding of maintained training gains at the 1-year follow-up and further extends the maintenance to 3 years. In addition, performance at the two followup sessions was significantly better than baseline (Week 1; M = 1.18, SD = 0.09). This was evident at both the 1-year (p = .043, d = 0.59) and 3-year follow-up sessions (p = .047, d = 0.42). Finally, the comparison between the two follow-up sessions revealed equivalent performance, p = .90 (d = 0.11).
Funding This work was supported by grants from the Faculty of Arts Scholarly, Research and Creative Activity research fund of Ryerson University and the Natural Sciences and Engineering Research Council of Canada Discovery Grant (371762–2009) awarded to L. Yang. Acknowledgments The authors wish to thank all of the research assistants involved in recruitment and data collection. Conflict of Interest This work is based, in part, on the research conducted for the PhD dissertation of the first author, A. J. Wilkinson. A. J. Wilkinson is currently a postdoctoral fellow at the Bridgepoint Collaboratory for Research and Innovation in Toronto, Canada.
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
Discussion Long-term maintenance of training benefits in inhibition was assessed in healthy older adults at 1- and 3-year follow-up time points after a 2-week (3 sessions per week) Stroop training program. The current data support the maintenance of training gains at both follow-up sessions. In other words, the reduction in Stroop ratio interference (indexing better inhibition) achieved during the second week of a 2-week Stroop training program was well maintained at both the 1- and 3-year follow-up sessions. Furthermore, it was found that performance at the two follow-up sessions did not differ from each other, and both were better than baseline. Taken together, these results suggest that the original training-induced performance gains in inhibition are durable and can be maintained for 1 year and even 3 years in older adults. In addition, performance at the two follow-up sessions is maintained at a level beyond baseline performance. The current results demonstrate that older adults are able to maintain small-to-medium inhibition training gains (ds = 0.42–0.62) over 1- and 3-year periods (using Cohen’s index of effect size; Cohen, 1988, 1992). In line with previous research (e.g., Dahlin et al., 2008; Stigsdotter Neely & Bäckman, 1993), the current findings support the durability of training gains across a comparable follow-up period. In the existing body of literature, the durability of executive function training gains has been demonstrated for a shorter period of time—ranging from 3 months (e.g., Li et al., 2008) up to 18 months (e.g., Dahlin et al., 2008). This study adds to the literature by extending the maintenance of executive function training (using a Stroop task training program) to 3 years. Going beyond previous findings, the results of this study indicate that performance is well maintained and still above baseline level even over a period of 3 years following the original training. Our results, however, do not support the conclusions drawn by Kelly and colleagues (2014) based on a review of the cognitive training literature, which suggest that booster sessions (as well as adaptive training) may be required to show durability of training effects. In contrast, the current findings demonstrate effective maintenance even in the absence of booster sessions or an original adaptive training program. Future research would benefit from empirically testing these hypotheses. Although this follow-up study makes substantial contributions to the literature, three limitations should be noted.
First, due to the small sample size, it is possible that significant attrition effects may have gone undetected. However, it has been demonstrated in a recent study (Salthouse, 2014) that selection attrition does not necessarily predict differential magnitude of longitudinal change. Based on this finding, despite the possibility of insufficient power to detect selective attrition effects on certain variables in this study, we argue that the magnitude of long-term maintenance of the training effect on Stroop task performance is unlikely to change even if there had been no attrition (i.e., assuming all participants returned for both follow-up sessions). Second, the sample size at the 3-year follow-up session—in particular—was small (n = 26); however, we were restricted to the number of participants who were willing to return for testing. Nevertheless, the sample size of the 3-year follow-up group still reflects a return rate of 61.9% from the original training group (n = 42). This retention rate is comparable with that of a follow-up study of similar duration (i.e., 3.5 years; Stigsdotter Neely & Bäckman, 1993). The third limitation is with respect to the generalizability of results. The study sample consisted of a group of healthy, well-educated, and high functioning older adults, which may not be representative of the typical older adult population. Given this, generalizability of the current findings may be limited. Regardless of these limitations, this study makes novel contributions to the literature by demonstrating that healthy older adults are able to maintain inhibition training gains for up to 3 years following the original training. Benefits in inhibitory processing, such as withholding an automatic but inappropriate response, can help to improve the daily lives of older adults. For example, if a doctor suddenly advises an individual to stop taking a certain medication that was previously taken regularly (e.g., every morning), efficient inhibition could help to minimize accidental ingestion, which may impact overall health and well-being. In conclusion, the current follow-up study adds to the literature by demonstrating long-term maintenance of training effects in inhibition above baseline levels 1 and 3 years following original training. Remarkably, this effect was shown using a single session of the Stroop task at each follow-up and without any booster sessions before the follow-up testing.
LONG-TERM MAINTENANCE OF INHIBITION TRAINING
Correspondence Correspondence should be addressed to Andrea J. Wilkinson, PhD, Department of Psychology, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada. E-mail: [email protected].
Gazzaley, A., Cooney, J. W., Rissman, J., & D’Esposito, M. (2005). Topdown suppression deficit underlies working memory impairment in normal aging. Nature Neuroscience, 8, 1298–1300. doi:10.1038/ nn1543 Gross, A. L., Rebok, G. W., Unverzagt, F. W., Willis, S. L., & Brandt, J. (2011). Cognitive predictors of everyday functioning in older adults: Results from the ACTIVE Cognitive Intervention Trial. The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 66, 557–566. doi:10.1093/geronb/gbr033 Günther, V. K., Schäfer, P., Holzner, B. J., & Kemmler, G. W. (2003). Long-term improvements in cognitive performance through computer-assisted cognitive training: A pilot study in a residential home for older people. Aging & Mental Health, 7, 200–206. doi:10.1080/1360786031000101175 Hamm, V. P., & Hasher, L. (1992). Age and the availability of inferences. Psychology and Aging, 7, 56–64. doi:10.1037/0882-7974.7.1.56 Harnishfeger, K. K. (1995). The development of cognitive inhibition: Theories, definitions, and research evidence. In F. N. Dempster & C. J. Brainerd (Eds.), Interference and inhibition in cognition (pp. 175–204). San Diego, CA: Academic Press. doi:10.1016/ B978-012208930-5/50007-6 Hasher, L., Lustig, C., & Zacks, R. (2007). Inhibitory mechanisms and the control of attention. In A. R. A. Conway, C. Jarrold, M. J., Kane, A. Miyake & J. N. Towse (Eds.), Variation in working memory (pp. 227–249). New York, NY: Oxford University Press. Hasher, L., Zacks, R. T., & May, C. P. (1999). Inhibitory control, circadian arousal, and age. In D. Gopher & A. Koriat (Eds.), Attention and performance XVII: Cognitive regulation of performance: Interaction of theory and application (pp. 653–675). Cambridge, MA: The MIT Press. Katzman, R., Brown, T., Fuld, P., Peck, A., Schechter, R., & Schimmel, H. (1983). Validation of a short Orientation-Memory-Concentration Test of cognitive impairment. The American Journal of Psychiatry, 140, 734–739. Kelly, M. E., Loughrey, D., Lawlor, B. A., Robertson, I. H., Walsh, C., & Brennan, S. (2014). The impact of cognitive training and mental stimulation on cognitive and everyday functioning of healthy older adults: A systematic review and meta-analysis. Ageing Research Reviews, 15, 28–43. doi:10.1016/j.arr.2014.02.004 Kramer, A. F., Hahn, S., & Gopher, D. (1999). Task coordination and aging: Explorations of executive control processes in the task switching paradigm. Acta Psychologica, 101, 339–378. doi:10.1016/ S0001-6918(99)00011-6 Kumada, T., Kitajima, M., Ogi, H., Akamatu, M., Tahira, H., & Yamazaki, H. (2005). The development of cognitive aging test for usability test: Focusing of attention and executive function for older adults [Japanese Abstract]. Proceedings of the Japanese Society for Cognitive Psychology, 3rd Meeting, 24. Kyoto, Japan: Japan Science and Technology Information Aggregator, Electronic (J-STAGE). Li, S. C., Schmiedek, F., Huxhold, O., Röcke, C., Smith, J., & Lindenberger, U. (2008). Working memory plasticity in old age: Practice gain, transfer, and maintenance. Psychology and Aging, 23, 731–742. doi:10.1037/a0014343 Logan, G. D. (1994). On the ability to inhibit thought and action: A user’s guide to the stop signal paradigm. In D. Dagenbach & T. H. Carr (Eds.), Inhibitory processes in attention, memory, and language (pp. 189–239). San Diego, CA: Academic Press, Inc. Nieuwenhuis, S., Ridderinkhof, K. R., de Jong, R., Kok, A., & van der Molen, M. W. (2000). Inhibitory inefficiency and failures of intention activation: Age-related decline in the control of saccadic eye movements. Psychology and Aging, 15, 635–647. doi:10.1037/0882-7974.15.4.635 Rebok, G. W., Ball, K., Guey, L. T., Jones, R. N., Kim, H.-Y., King, J. W., . . ., Willis, S. L. (2014). Ten-year effects of the Advanced Cognitive Training for Independent and Vital Elderly Cognitive Training trial
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
References Ball, K., Berch, D. B., Helmers, K. F., Jobe, J. B., Leveck, M. D., Marsiske, M.,…Willis, S. L. (2002). Effects of cognitive training interventions with older adults: A randomized controlled trial. The Journal of the American Medical Association, 288, 2271–2281. doi:10.1001/ jama.288.18.2271 Baltes, P. B., & Lindenberger, U. (1988). On the range of cognitive plasticity in old age as a function of experience: 15 years of intervention research. Behavior Therapy, 19, 283–300. doi:10.1016/ S0005-7894(88)80003-0 Beck, A. T., Epstein, N., Brown, G., & Steer, R. A. (1988). An inventory for measuring clinical anxiety: Psychometric properties. Journal of Consulting and Clinical Psychology, 56, 893–897. doi:10.1037/0022-006X.56.6.893 Biss, R. K., Campbell, K. L., & Hasher, L. (2013). Interference from previous distraction disrupts older adults’ memory. The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 68, 558–561. doi:10.1093/geronb/gbs074 Bojko, A., Kramer, A. F., & Peterson, M. S. (2004). Age equivalence in switch costs for prosaccade and antisaccade tasks. Psychology and Aging, 19, 226–234. doi:10.1037/0882-7974.19.1.226 Borella, E., Carretti, B., Riboldi, F., & De Beni, R. (2010). Working memory training in older adults: Evidence of transfer and maintenance effects. Psychology and Aging, 25, 767–778. doi:10.1037/a0020683 Brehmer, Y., Westerberg, H., & Bäckman, L. (2012). Working-memory training in younger and older adults: Training gains, transfer, and maintenance. Frontiers in Human Neuroscience, 6, 63. doi:10.3389/ fnhum.2012.00063 Butler, K. M., & Zacks, R. T. (2006). Age deficits in the control of prepotent responses: Evidence for an inhibitory decline. Psychology and Aging, 21, 638–643. doi:10.1037/0882-7974.21.3.638 Cohen, J. (1988). Statistical power analysis for the behavioral sciences (2nd ed.). Hillsdale, NJ: Lawrence Erlbaum Associates, Inc. Cohen, J. (1992). A power primer. Psychological Bulletin, 112, 155–159. doi:10.1037/0033-2909.112.1.155 Dahlin, E., Nyberg, L., Bäckman, L., & Neely, A. S. (2008). Plasticity of executive functioning in young and older adults: Immediate training gains, transfer, and long-term maintenance. Psychology and Aging, 23, 720–730. doi:10.1037/a0014296 Davidson, D. J., Zacks, R. T., & Williams, C. C. (2003). Stroop interference, practice, and aging. Neuropsychology, Development, and Cognition, 10, 85–98. doi:10.1076/anec.10.2.85.14463 Donders, F. C. (1969). On the speed of mental processes. In W. G. Koster (Ed.), Attention and performance II (pp. 412–431). Amsterdam, The Netherlands: North-Holland Publishing Co. (Original work published in 1868). Dulaney, C. L., & Rogers, W. A. (1994). Mechanisms underlying reduction in Stroop interference with practice for young and old adults. Journal of Experimental Psychology, 20, 470–484. doi:10.1037/0278-7393.20.2.470 Dunlap, W. P., Cortina, J. M., Vaslow, J. B., & Burke, M. J. (1996). Meta-analysis of experiments with matched groups or repeated measures designs. Psychological Methods, 1, 170–177. doi:10.1037/1082-989X.1.2.170 Dvorine, I. (1953). Dvorine pseudo-isochromatic plates [Apparatus] (2nd ed.). Baltimore, MD: Harcourt, Brace & World, Inc. Fan, J., McCandliss, B. D., Sommer, T., Raz, A., & Posner, M. I. (2002). Testing the efficiency and independence of attentional networks. Journal of Cognitive Neuroscience, 14, 340–347. doi:10.1162/089892902317361886
Page 7 of 8
Page 8 of 8
WILKINSON AND YANG
Verhaeghen, P. (2011). Aging and executive control: Reports of a demise greatly exaggerated. Current Directions in Psychological Science, 20, 174–180. doi:10.1177/0963721411408772 Wilkinson, A. J., & Yang, L. (2012). Plasticity of inhibition in older adults: Retest practice and transfer effects. Psychology and Aging, 27, 606– 615. doi:10.1037/a0025926 Willis, S. L., & Nesselroade, C. S. (1990). Long-term effects of fluid ability training in old-old age. Developmental Psychology, 26, 905–910. doi:10.1037/0012-1649.26.6.905 Willis, S. L., Tennstedt, S. L., Marsiske, M., Ball, K., Elias, J., Koepke, K. M.,…Wright, E. (2006). Long-term effects of cognitive training on everyday functional outcomes in older adults. Journal of American Medical Association, 296, 2805–2814. doi:10.1001/ jama.296.23.2805 Yang, L., & Hasher, L. (2007). The enhanced effects of pictorial distraction in older adults. The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 62, P230–P233. doi:10.1093/ geronb/62.4.P230 Yang, L., & Krampe, R. T. (2009). Long-term maintenance of retest learning in young old and oldest old adults. The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 64, 608–611. doi:10.1093/geronb/gbp063
Downloaded from http://psychsocgerontology.oxfordjournals.org/ at Main Library of Gazi University on May 2, 2015
on cognition and everyday functioning in older adults. Journal of the American Geriatrics Society, 62, 16–24. doi:10.1111/jgs.12607 Rosenbaum, J. G. (1976). Rosenbaum Pocket Vision Screener [Apparatus]. Cleveland, OH: Design courtesy of J. G. Rosenbaum, M. D. Rowe, G., Valderrama, S., Hasher, L., & Lenartowicz, A. (2006). Attentional dysregulation: A benefit for implicit memory. Psychology and Aging, 21, 826–830. doi:10.1037/0882-7974.21.4.826 Salthouse, T. A. (2014). Selectivity of attrition in longitudinal studies of cognitive functioning. The Journals of Gerontology, Series B: Psychological Sciences and Social Sciences, 69, 567–574. doi:10.1093/geronb/gbt046 Schwartz, K., & Verhaeghen, P. (2008). ADHD and Stroop interference from age 9 to age 41 years: A meta-analysis of developmental effects. Psychological Medicine, 38, 1607–1616. doi:10.1017/S003329170700267X Shipley, W. C. (1940). A self-administering scale for measuring intellectual impairment and deterioration. Journal of Psychology, 9, 371– 377. doi:10.1080/00223980.1940.9917704 Stigsdotter Neely, A. S., & Bäckman, L. (1993). Long-term maintenance of gains from memory training in older adults: Two 3 ½-year follow-up studies. Journal of Gerontology, 48, P233–P237. doi:10.1093/geronj/48.5.P233 Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18, 643–662. doi:10.1037/h0054651
