International Journal of Psychology, 2016 Vol. 51, No. 2, 117–122, DOI: 10.1002/ijop.12117
Are attentional resources a mediator for sex differences in memory? ˘ Ilmiye Seçer and Yüksel Yılmazogulları Department of Psychology, Eastern Mediterranean University, Famagusta, North Cyprus
T
he divided attention paradigm was used to investigate sex differences in encoding and retrieval processes of memory. Participants performed a memory and reaction time (RT) task under full attention and two divided attention conditions, that is, at encoding and retrieval. Results revealed that females recalled significantly more words than males under the full attention and divided attention at encoding conditions. Results further showed that secondary task costs were larger for males than females during divided attention at retrieval. Furthermore, regardless of sex, recall was best under full attention and worst under divided attention at encoding conditions. In relation to the RT task, RTs were shorter under full attention and longer under the divided attention at retrieval condition. Overall, these results show that females recall more words than males possibly due to a more severe effect of reduced attention during encoding than retrieval for males. The current findings thus suggest that a reduction in attentional resources may mediate sex-related decreases in word recall.
Keywords: Encoding and retrieval processes; Divided attention paradigm; Attentional resources; Reaction time task; Sex differences.
Sex differences in memory are well documented by experimental studies. Robust findings (Herlitz & Rehnman, 2008; Herlitz & Yonker, 2002; Larsson, Lovden, & Nilsson, 2003) reveal enhanced verbal abilities for females such as improved recall for living categories (e.g. animals, fruits) (Laws, 2004) and episodic memory tasks that are attention demanding (e.g. recall tasks) (Nyberg, Habib, & Herlitz, 2000). Emerging research illustrates that sex differences in recall arise from differences in the encoding of new information rather than problems related to the ability to retrieve information (Herlitz, Nilsson, & Backman, 1997; Krueger & Salthouse, 2010). In particular, females in comparison to males have been found to perform greater semantic processing (Guillem & Mograss, 2005; Meyers-Levy & Maheswaran, 1991) which leads to superior recall. According to the Attentional Resource Theory (Craik, 1983; Craik & Byrd, 1982), attentional resources are required to encode and retrieve information effectively. Under certain circumstances (e.g. old age) when attentional resources decrease, the ability to encode and retrieve information becomes hindered. In light of this, it may be possible that reductions in attention may mediate reduced ability to encode and retrieve information among the sexes. One possible method to examine for this is to divide attention at the time of encoding and retrieval by
performing a secondary task and assess memory. The divided attention paradigm has been used to examine encoding and retrieval processes of memory (Anderson, Craik, & Naveh-Benjamin, 1998; Park, Smith, Dudley, & Lafronza, 1989). Past research has shown that when attention is diverted away from the memory task at the time of encoding, performance is affected by up to 48% (Craik, Govoni, Naveh-Benjamin, & Anderson, 1996). This is because fewer attentional resources are allocated to encoding, thereby preventing elaborative rehearsal and in turn affecting recall. On the other hand, divided attention at the time of retrieval only slightly affects memory performance (approximately 16%) (Craik et al., 1996; Naveh-Benjamin, Kilb, & Fisher, 2006). Decrements in secondary task performance however reflect the attentional demands of retrieval processes (Craik et al., 1996). Past findings have shown larger secondary task costs (i.e. increased RTs during divided attention conditions in comparison to full attention conditions) at both encoding and retrieval for older adults than younger adults that reflect a reduction in their attentional resources (Craik et al., 1996). To date, three studies (Herlitz et al., 1997; Loven, Herlitz, & Rehnman, 2011; Palmer, Brewer, & Horry, 2013) have examined sex differences in memory under full attention and divided attention conditions. For example,
Correspondence should be addressed to Ilmiye Seçer, Department of Psychology, Eastern Mediterranean University, Famagusta, North Cyprus, Mersin 10, Turkey. (E-mail: [email protected]).
© 2014 International Union of Psychological Science
118
˘ SEÇER AND YILMAZOGULLARI
Herlitz et al. (1997) assessed memory performance using a word recall task while the secondary task consisted of a card-sorting task. Results from Herlitz et al.’s (1997) study showed that women recalled more words than men under all conditions, that is, full attention and divided attention at encoding and retrieval conditions. Likewise Palmer et al. (2013) found that females’ improved ability to recognise female faces as opposed to male faces reduced after dividing attention at encoding. Such results were interpreted to reflect the importance of attention in enabling effortful processing of female faces. Loven et al. (2011) however found that own-gender bias in face recognition memory was not reduced under divided attention conditions. Instead females’ improved ability to recognise female faces compared to male faces was due to greater perceptual expertise rather than the effortful processing of female faces. The mixed findings regarding the role of attention in meditating females’ enhanced ability to recognise and recall information warrants further research. In light of previous research (e.g. Herlitz et al., 1997; Krueger & Salthouse, 2010; Palmer et al., 2013), it is plausible to assert that females have enhanced ability to selectively attend to and encode information relative to males and this facilitates their memory performance. Palmer et al. (2013) did not assess sex differences in memory under divided attention at retrieval conditions. The absence of such information precludes any discussion regarding the attentional demands of retrieval processes for males and females. If reductions in attention account for sex-related differences in word recall such information would clarify whether males’ decreased word recall is due to difficulties in performing controlled processes during encoding (e.g. elaborative encoding) or retrieval (e.g. controlled search of long-term memory). Furthermore, based on these findings (i.e. Herlitz et al., 1997; Palmer et al., 2013), it is difficult to determine whether sex-related differences in memory are mediated by reductions in attention. This is because Herlitz et al. (1997) used a card-sorting task that restricted the analysis of secondary task costs, that is, performance decrements on the secondary task in divided attention conditions relative to full attention conditions. Similarly, although Palmer et al. (2013) used a secondary tone-monitoring task, secondary task costs were not analysed. According to Anderson (1999), secondary task costs are important because they reveal reductions in the pool of available attentional resources utilised for deep semantic encodings and retrieval operations such as cue search. To examine such costs a reaction time (RT) task as the secondary task is sufficient. This study therefore adopted the divided attention paradigm to assess memory performance among males and females under reduced attention conditions. This
paradigm required participants to perform a verbal memory task presented in an auditory mode while concurrently performing a visual-spatial RT task under different attentional conditions. Expectations of this study included higher levels of word recall for females than males under conditions of full attention, divided attention at encoding and divided attention at retrieval. Furthermore, it was expected that if sex differences in word recall are due to reductions in attentional resources, males would have larger secondary task costs at encoding and retrieval than females. METHOD Participants One hundred and forty-three participants (74 male, 69 female) aged between 18 and 28 years (M = 22.31, SD = 1.78) were recruited from Eastern Mediterranean University. Participants were Turkish and Turkish-Cypriot undergraduate university students who were all right handed, had normal hearing and either normal or corrected vision. Experimental tasks Word lists for the memory task Fifty-five discrete, highly frequent Turkish words that were two to three syllables in length were derived for the memory task from the word lists used in picture naming in a Turkish population (Raman, 2011; Raman & Weekes, 2005). No word was repeated in any of the lists, such that practice effects did not interfere with recall. A total of four word lists were prepared including three for the experimental and one for the practice trials. The experimental word lists consisted of 15 words, whereas the practice list included 10 words (fewer words were included in the practice list to reduce boredom and fatigue). Distraction task: Arithmetic filler task To eliminate the recency effect, a distractor task was employed. Participants performed an arithmetic filler task between the presentation of the word lists and the testing of recall. Participants were presented with 10 numbers randomly selected between 1 and 50 at a presentation rate of one number per second and asked to add three to each digit and report the sum orally. Marks were not lost for incorrect calculations or gained for accurately reporting the calculations. RT task The RT task was used as the secondary task in the measurement of the faculty of divided attention. The RT © 2014 International Union of Psychological Science
SEX DIFFERENCES IN MEMORY
from the onset of to the completion of each trial was recorded by a computer program with millisecond accuracy. For the RT task, four large boxes were displayed on the computer screen and in one of the boxes an asterisks randomly appeared. Each box corresponded to a different key on the keyboard and participants’ task was to press the correct corresponding key on the keyboard to the box in which the asterisks was appearing. Participants were instructed to perform this task as accurately and quickly as possible. Procedure Ethical approval was obtained from Eastern Mediterranean University, Department of Psychology, Research and Ethics Committee and all participants provided informed consent. Thereafter, participants practiced on all tasks including the memory task, distraction task and RT task under full attention, divided attention at encoding and divided at retrieval conditions (performed respectively only for the practice sessions). Following the practice session, the experimental session began. The total duration of testing for each participant was approximately 30 minutes, including the practice session and all testing was carried out in the afternoon. At the completion of the study, participants were thanked for their participation. The memory task was performed under three different attention conditions at encoding and retrieval, which included full attention, divided attention at encoding and divided attention at retrieval, respectively. The order of the conditions was counterbalanced across participants. To obtain participants’ baseline RT, the RT task was performed under full attention conditions at the beginning of each experimental session. Experimental sessions For all three experimental conditions (i.e. full attention, divided attention at encoding and divided attention at retrieval), the memory task began when the experimenter read aloud a list of 15 words at a rate of 4 seconds per word (encoding phase), followed by the performance of the distractor task. Thereafter, during the retrieval phase, participants verbally recalled as many of the words from the list in any order. For the full attention condition, participants performed the memory task without performing the secondary RT task. The RT task was performed for exactly 1 minute under full attention conditions prior to the completion of the memory task. For the divided attention at encoding condition, participants performed the RT task only during the encoding phase, whereas for the divided attention at retrieval condition the RT task was performed only during the retrieval phase. Participants were instructed to place equal emphasis on the RT and © 2014 International Union of Psychological Science
119
memory task and had approximately 2 minutes to verbally recall the words. The experiment ceased when the participant indicated that they could not remember any more words or when 2 minutes elapsed. RESULTS Performance on both the memory task (i.e. words recalled) and the secondary task (i.e. RTs) was measured under full attention and divided attention conditions and compared amongst the sexes. Therefore, any differences in the memory task and secondary task under the different attention conditions were the dependent variables with sex as the fixed factor. To determine the impact of reduced attention on the ability to encode and retrieve information, Cohen’s d effects sizes are further reported for males and females memory task performance during divided attention at encoding and retrieval. To assess secondary task costs, Cohen’s d is reported for sex-related differences in RT task performance during divided attention conditions compared to full attention conditions. Positive effect sizes indicate larger costs (i.e. greater decrement in RT task performance during divided attention conditions in comparison to the full attention condition) for males than females; negative effect sizes indicate the reverse. An alpha level of .05 was used for all the statistical inferential tests. A 2 (sex: male, female) × 3 (attention condition: full attention, divided attention at encoding and divided attention at retrieval) mixed design univariate analysis of variance (ANOVA) was run for both the recall task and RT task. Reaction time (RT) The 2 × 3 ANOVA results revealed a significant main effect for attention condition, F(1, 142) = 304.34, p < .001, ηp2 = .683, such that RTs were significantly shorter under the full attention condition (M = 743.37, SD = 118.54) than the divided attention at encoding (M = 1033.01, SD = 263.21) and divided attention at retrieval condition (M = 1243.67, SD = 292.75), p < .001. RTs were also significantly shorter under the divided attention at encoding than the divided attention at retrieval condition (p < .001). Furthermore, there was a significant main effect for sex, F(1, 142) = 7.34, p = .008, ηp2 = .050, indicating that overall females (M = 962.86, SD = 186.50) had faster RTs than males (M = 1047.54, SD = 186.62). The interaction between sex and attention condition was also significant, F(1, 142) = 3.32, p = .037, ηp2 = .023 for RT task performance. The interaction indicated that the sex differences in full attention RTs (d = 0.41) were more pronounced during the divided attention at retrieval condition (d = 0.51) than the divided attention at encoding condition (d = 0.23).
120
˘ SEÇER AND YILMAZOGULLARI
TABLE 1 Word recall (#correct) and reaction time (RTs; ms) in males and females under full attention and divided attention at encoding and retrieval. Means (SD)
Sex
Males M (SD)
Full attention Word recall 6.56 (1.88)* Secondary task RT 766.49 (136.88)* Divided attention at encoding Word recall 4.01 (1.59)* Secondary task RT 1062.71 (290.04) Divided attention at retrieval Word recall 4.90 (1.68) Secondary task RT 1313.43 (337.86)*
Females M (SD) 7.31 (1.98)* 718.57 (89.57)* 5.01 (1.77)* 1001.17 (228.86) 5.05 (1.75) 1168.85 (213.17)*
*p < .05.
Word recall The 2 × 3 ANOVA results revealed a significant main effect for sex, F(1, 142) = 8.21, p = .005, ηp2 = .055, indicating that overall females (M = 5.79, SD = 1.2) recalled more words than males (M = 5.16, SD = 1.29). Furthermore, a significant main effect for attention condition was found, F(1, 142) = 110.85, p < .001, ηp2 = .440, indicating that participants significantly recalled a greater number of words under the full attention condition (M = 6.94, SD = 1.91) than the divided attention at encoding (M = 4.51, SD = 1.67), p < .001, and the divided attention at retrieval condition (M = 4.98, SD = 0.1.67), p < .001. Word recall was also significantly higher in the divided attention at retrieval condition than the divided attention at encoding condition (p = .008). Furthermore, there was a significant interaction between sex and attention condition, F(1, 142) = 3.14, p = .043, ηp2 = .022. Females significantly recalled a greater number of words than males under the full attention (d = 0.38) and the divided attention at encoding condition (d = 0.59) but not the divided attention at retrieval condition (d = 0.09; see Table 1). This differential impact of divided attention on the sex differences in recall appears to be due to a larger negative impact of divided attention during encoding for males than females relative to the full attention condition. Specifically, males’ recall was significantly worse during divided attention at encoding (d = 1.46) than at retrieval (d = 0.93), whereas females’ reduction in performance was more similar between divided attention at encoding (d = 1.22) and at retrieval (d = 1.20). DISCUSSION This study examined sex differences in memory in light of the attentional resources framework (Craik & Byrd, 1982). It was expected that females would have a higher level of word recall under the following conditions: full attention, divided attention at encoding and
divided attention at retrieval. It was further expected that if sex differences in word recall reflect reductions in the available pool of attentional resources, then males would have larger secondary task costs at encoding and retrieval than females (i.e. longer RT performance in the divided attention conditions compared to the full attention condition). These expectations were partially supported. Findings of this study showed that females recalled a greater number of words in the full attention condition compared to males. Although both males and females experienced a decrease in word recall during divided attention conditions compared to full attention, females still recalled a greater number of words than males under divided attention at encoding but not divided attention at retrieval. That is, males’ drop in recall during divided attention at encoding was more severe than their drop in recall at retrieval compared to full attention, whereas females’ drop in recall during divided attention at encoding and retrieval compared to full attention was comparable. Such findings suggest that the sex differences in recall may be due to a greater effect of reduced attention during encoding than retrieval for males. With regard to the secondary RT task, females had shorter RTs than males during full attention. Females also had shorter RTs than males during divided at retrieval but not encoding when compared to full attention. Males, therefore, had larger secondary task costs (i.e. longer RTs) than females during divided attention at retrieval but not encoding. The current pattern of results suggests that males and females may differentially manage the performance of two concurrent tasks (i.e. the memory and secondary RT task). Research shows that concurrent tasks compete for a limited resource: attention (Barrouillet, Bernardin, & Camos, 2004; Barrouillet & Camos, 2012). When attention is switched away from a particular task (e.g. memory task) a decline in performance for that task begins (e.g. memory traces decline), yet can be refreshed before being completely lost by refocusing attention on that task (Barrouillet et al., 2004). As a consequence, attention is switched between tasks and can lead to a tradeoff between the two activities. Although participants in this study were requested to place equal emphasis on both tasks, it may be that participants did not confirm to this request. Therefore, males attended more to the secondary task during divided attention at encoding thereby improving their RT performance compared to females but reducing their ability to attend to the words resulting in worse recall. During divided attention at retrieval, however, males compensate for their relatively poor attention during encoding (reflected in their lower rates of word recall in the divided attention at encoding condition) by spending more time conducting a controlled search of memory that improved their recall, but at the expense of the secondary task (thereby resulting in longer RTs than females). Such findings indicate that © 2014 International Union of Psychological Science
SEX DIFFERENCES IN MEMORY
males and females may differentially manage the tradeoff between the memory and secondary RT task. Future research using a task emphasis manipulation is warranted to confirm this proposition. With regard to sex differences in word recall, the current findings are in line with past studies that show that females compared to males have superior word recall because they encode information more effectively (Guillem & Mograss, 2005; Krueger & Salthouse, 2010; Meyers-Levy & Maheswaran, 1991). To extend research in this area, this study aimed to determine whether males’ reduced ability to encode words effectively could be accounted for by a reduction in their attentional resources compared to females. In line with past research (Anderson, 1999), this study expected larger secondary task costs (i.e. longer RTs during divided attention conditions compared to full attention) at encoding and retrieval for males than females. This study indicated larger secondary task costs (i.e. longer RTs) for males than females during divided attention at retrieval but not at encoding. Therefore, expectations regarding secondary task costs were partially supported. Such findings suggest that reductions in attention may account for sex differences in word recall. Males compared to females’ may have a reduction in their pool of attentional resources, which may yield difficulties for males to perform controlled processes mainly during encoding (e.g. elaborative encoding). However, the larger secondary task costs at retrieval for males may simply be associated with increased response production costs rather than a reduction in attention (Craik et al., 1996). This therefore warrants the need for further research. According to the environmental support theory (Craik, 1983), memory tasks that provide environmental cues (e.g. recognition tasks) are easier to perform since they require less self-initiated processes that are resource demanding, as in free recall and cued recall tasks. As a result, any recall differences due to reductions in attention should be compensated by recognition tasks. Findings of Herlitz et al. (1997), however, showed that females recalled more words than males when tested with a free recall task, cued recall task and a recognition task. To clarify whether increased secondary task costs reflect production costs or a reduction in attention, future studies could employ a response conflict task. If males’ RTs during this task are slower or do not differ from their RTs in the full attention condition then increased RTs during retrieval are less likely to be accounted for by response production costs (Craik et al., 1996).This would strengthen the argument that sex-related differences in attention do exist. Future research is therefore needed to examine sex-related differences in attentional resources. The current results further reveal that both word recall was greater and RT scores were slower when attention was divided at retrieval than encoding. A possible limitation could be that the time allowed to perform the RT task © 2014 International Union of Psychological Science
121
across the conditions (i.e. 1 minute for the full attention and divided attention at encoding, and 2 minutes for the divided attention at retrieval) was not equivalent. However, past studies (e.g. Craik et al., 1996; Naveh-Benjamin et al., 2006) indicate that divided attention more negatively impacts recall when implemented during encoding rather than retrieval. Therefore, a decrease in attentional resources at the time of encoding affects word recall. Although word recall is spared when attention is divided at retrieval reductions in attention are manifested by an increase in secondary task performance. In line with this, results of this study also show that for both sexes word recall was best under full attention conditions and worst under divided attention at encoding and RTs were faster under full attention conditions and slowest under the divided attention at retrieval condition, replicating those of past research (i.e. Anderson, 1999; Craik et al., 1996) that show a differential effect of divided attention on encoding and retrieval processes. Such explanations also account for the current findings showing no sex differences in word recall during divided attention at retrieval. Furthermore, it is important to note that the power to detect sex-related differences in RT costs when attention was divided at encoding was low (.07). This could account for the non-significant secondary task cost findings during divided attention at encoding. A larger sample size may reveal sex-related differences in attentional resources. Overall, the current findings show that females outperformed males in the number of words that were remembered under both full attention and divided attention at encoding conditions. Females also had shorter RTs than males when attention was divided at retrieval but not encoding. These findings suggest that males and females may differentially manage the tradeoff between the memory and secondary RT task. Furthermore, secondary task costs were larger for males than females when attention was divided at retrieval. This finding suggests that there may be a reduction in the pool of attentional resources retained by males. Future research is however needed to verify these findings. Further research is also required to determine whether sex-related differences in word recall could be accounted for by sex-related differences in the cognitive control of attention. This could be examined by employing the divided attention paradigm and varying task emphasis for the primary and secondary task under three conditions, that is, primary task emphasis, secondary task emphasis, equal emphasis between the primary and secondary task (Craik et al., 1996). Any sex-related differences in RT costs under task emphasis conditions during encoding would suggest sex differences in the ability to allocate necessary attentional resources to memory tasks effectively. Manuscript received December 2013 Revised manuscript accepted October 2014 First published online November 2014
122
˘ SEÇER AND YILMAZOGULLARI
REFERENCES Anderson, N. D. (1999). The attentional demands of encoding and retrieval in younger and older adults: 2 Evidence from secondary task reaction time distributions. Psychology and Aging, 14(4), 645–655. Anderson, N. D., Craik, F. I. M., & Naveh-Benjamin, M. (1998). The attentional demands of encoding and retrieval in younger and older adults: 1. Evidence from divided attention costs. Psychology and Aging, 13(3), 405–423. Barrouillet, P., Bernardin, S., & Camos, V. (2004). Time constraints and resource sharing in adults’ working memory spans. Journal of Experimental Psychology: General, 133(1), 83–100. Barrouillet, P., & Camos, V. (2012). As time goes by: Temporal constraints in working memory. Current Directions in Psychological Science, 21(6), 413–419. Craik, F. I. M. (1983). On the transfer of information from temporary to permanent memory. Philosophical Transactions of the Royal Society of London, Series B, 302, 341–359. Craik, F. I. M., & Byrd, M. (1982). Aging and cognitive deficits: The role of attentional resources. In F. I. M. Craik & S. Trehub (Eds.), Aging and cognitive processes (pp. 191–211). New York, NY: Plenum. Craik, F. I. M., Govoni, R., Naveh-Benjamin, M., & Anderson, N. D. (1996). The effect of divided attention on encoding and retrieval processes in human memory. Journal of Experimental Psychology: General, 125(2), 159–180. Guillem, F., & Mograss, M. (2005). Gender differences in memory processing: Evidence from event-relate potential to faces. Brain and Cognition, 57, 84–92. Herlitz, A., Nilsson, L., & Backman, L. (1997). Gender differences in episodic memory. Memory and Cognition, 25(6), 801–811. Herlitz, A., & Rehnman, J. (2008). Sex differences in episodic memory. Current Directions in Psychological Science, 17(1), 52–56. Herlitz, A., & Yonker, J. E. (2002). Sex differences in episodic memory: The influence of intelligence. Journal of Clinical and Experimental Neuropsychology, 24(1), 107–114.
Krueger, L. E., & Salthouse, T. A. (2010). Differences in acquisition, not retention, largely contribute to sex difference in multitrial word recall performance. Personality and Individual Differences, 49, 768–772. Larsson, M., Lovden, M., & Nilsson, L. (2003). Sex differences in recollective experience for olfactory and verbal information. Acta Psychologica, 112, 89–103. Laws, K. R. (2004). Sex differences in lexical size across semantic categories. Personality and Individual Differences, 36, 23–32. Loven, J., Herlitz, A., & Rehnman, J. (2011). Women’s own-gender bias in face recognition memory: The role of attention at encoding. Experimental Psychology, 58(4), 333–340. Meyers-Levy, J., & Maheswaran, D. (1991). Exploring differences in males and females processing strategies. Journal of Consumer Research, 18, 63–70. Naveh-Benjamin, M., Kilb, A., & Fisher, T. (2006). Concurrent task effects on memory encoding and retrieval: Further support for an asymmetry. Memory and Cognition, 34(1), 90–101. Nyberg, L., Habib, R., & Herlitz, A. (2000). Brain activation during episodic memory retrieval: Sex differences. Acta Psychologica, 105, 181–194. Palmer, M. A., Brewer, A., & Horry, R. (2013). Understanding gender bias in face recognition: Effects of divided attention at encoding. Acta Psychologica, 142, 362–369. Park, D. C., Smith, A. D., Dudley, W. N., & Lafronza, V. N. (1989). Effects of age and a divided attention task presented during encoding and retrieval on memory. Journal of Experimental Psychology: Learning, Memory and Cognition, 15(6), 1185–1191. Raman, I. (2011). The role of age of acquisition in picture and word naming in dyslexic adults. British Journal of Psychology, 102, 328–339. Raman, I., & Weekes, B. S. (2005). Acquired dyslexia in a Turkish-English speaker. Annals of Dyslexia, 55(1), 79–104.
© 2014 International Union of Psychological Science
Are attentional resources a mediator for sex differences in memory? ˘ Ilmiye Seçer and Yüksel Yılmazogulları Department of Psychology, Eastern Mediterranean University, Famagusta, North Cyprus
T
he divided attention paradigm was used to investigate sex differences in encoding and retrieval processes of memory. Participants performed a memory and reaction time (RT) task under full attention and two divided attention conditions, that is, at encoding and retrieval. Results revealed that females recalled significantly more words than males under the full attention and divided attention at encoding conditions. Results further showed that secondary task costs were larger for males than females during divided attention at retrieval. Furthermore, regardless of sex, recall was best under full attention and worst under divided attention at encoding conditions. In relation to the RT task, RTs were shorter under full attention and longer under the divided attention at retrieval condition. Overall, these results show that females recall more words than males possibly due to a more severe effect of reduced attention during encoding than retrieval for males. The current findings thus suggest that a reduction in attentional resources may mediate sex-related decreases in word recall.
Keywords: Encoding and retrieval processes; Divided attention paradigm; Attentional resources; Reaction time task; Sex differences.
Sex differences in memory are well documented by experimental studies. Robust findings (Herlitz & Rehnman, 2008; Herlitz & Yonker, 2002; Larsson, Lovden, & Nilsson, 2003) reveal enhanced verbal abilities for females such as improved recall for living categories (e.g. animals, fruits) (Laws, 2004) and episodic memory tasks that are attention demanding (e.g. recall tasks) (Nyberg, Habib, & Herlitz, 2000). Emerging research illustrates that sex differences in recall arise from differences in the encoding of new information rather than problems related to the ability to retrieve information (Herlitz, Nilsson, & Backman, 1997; Krueger & Salthouse, 2010). In particular, females in comparison to males have been found to perform greater semantic processing (Guillem & Mograss, 2005; Meyers-Levy & Maheswaran, 1991) which leads to superior recall. According to the Attentional Resource Theory (Craik, 1983; Craik & Byrd, 1982), attentional resources are required to encode and retrieve information effectively. Under certain circumstances (e.g. old age) when attentional resources decrease, the ability to encode and retrieve information becomes hindered. In light of this, it may be possible that reductions in attention may mediate reduced ability to encode and retrieve information among the sexes. One possible method to examine for this is to divide attention at the time of encoding and retrieval by
performing a secondary task and assess memory. The divided attention paradigm has been used to examine encoding and retrieval processes of memory (Anderson, Craik, & Naveh-Benjamin, 1998; Park, Smith, Dudley, & Lafronza, 1989). Past research has shown that when attention is diverted away from the memory task at the time of encoding, performance is affected by up to 48% (Craik, Govoni, Naveh-Benjamin, & Anderson, 1996). This is because fewer attentional resources are allocated to encoding, thereby preventing elaborative rehearsal and in turn affecting recall. On the other hand, divided attention at the time of retrieval only slightly affects memory performance (approximately 16%) (Craik et al., 1996; Naveh-Benjamin, Kilb, & Fisher, 2006). Decrements in secondary task performance however reflect the attentional demands of retrieval processes (Craik et al., 1996). Past findings have shown larger secondary task costs (i.e. increased RTs during divided attention conditions in comparison to full attention conditions) at both encoding and retrieval for older adults than younger adults that reflect a reduction in their attentional resources (Craik et al., 1996). To date, three studies (Herlitz et al., 1997; Loven, Herlitz, & Rehnman, 2011; Palmer, Brewer, & Horry, 2013) have examined sex differences in memory under full attention and divided attention conditions. For example,
Correspondence should be addressed to Ilmiye Seçer, Department of Psychology, Eastern Mediterranean University, Famagusta, North Cyprus, Mersin 10, Turkey. (E-mail: [email protected]).
© 2014 International Union of Psychological Science
118
˘ SEÇER AND YILMAZOGULLARI
Herlitz et al. (1997) assessed memory performance using a word recall task while the secondary task consisted of a card-sorting task. Results from Herlitz et al.’s (1997) study showed that women recalled more words than men under all conditions, that is, full attention and divided attention at encoding and retrieval conditions. Likewise Palmer et al. (2013) found that females’ improved ability to recognise female faces as opposed to male faces reduced after dividing attention at encoding. Such results were interpreted to reflect the importance of attention in enabling effortful processing of female faces. Loven et al. (2011) however found that own-gender bias in face recognition memory was not reduced under divided attention conditions. Instead females’ improved ability to recognise female faces compared to male faces was due to greater perceptual expertise rather than the effortful processing of female faces. The mixed findings regarding the role of attention in meditating females’ enhanced ability to recognise and recall information warrants further research. In light of previous research (e.g. Herlitz et al., 1997; Krueger & Salthouse, 2010; Palmer et al., 2013), it is plausible to assert that females have enhanced ability to selectively attend to and encode information relative to males and this facilitates their memory performance. Palmer et al. (2013) did not assess sex differences in memory under divided attention at retrieval conditions. The absence of such information precludes any discussion regarding the attentional demands of retrieval processes for males and females. If reductions in attention account for sex-related differences in word recall such information would clarify whether males’ decreased word recall is due to difficulties in performing controlled processes during encoding (e.g. elaborative encoding) or retrieval (e.g. controlled search of long-term memory). Furthermore, based on these findings (i.e. Herlitz et al., 1997; Palmer et al., 2013), it is difficult to determine whether sex-related differences in memory are mediated by reductions in attention. This is because Herlitz et al. (1997) used a card-sorting task that restricted the analysis of secondary task costs, that is, performance decrements on the secondary task in divided attention conditions relative to full attention conditions. Similarly, although Palmer et al. (2013) used a secondary tone-monitoring task, secondary task costs were not analysed. According to Anderson (1999), secondary task costs are important because they reveal reductions in the pool of available attentional resources utilised for deep semantic encodings and retrieval operations such as cue search. To examine such costs a reaction time (RT) task as the secondary task is sufficient. This study therefore adopted the divided attention paradigm to assess memory performance among males and females under reduced attention conditions. This
paradigm required participants to perform a verbal memory task presented in an auditory mode while concurrently performing a visual-spatial RT task under different attentional conditions. Expectations of this study included higher levels of word recall for females than males under conditions of full attention, divided attention at encoding and divided attention at retrieval. Furthermore, it was expected that if sex differences in word recall are due to reductions in attentional resources, males would have larger secondary task costs at encoding and retrieval than females. METHOD Participants One hundred and forty-three participants (74 male, 69 female) aged between 18 and 28 years (M = 22.31, SD = 1.78) were recruited from Eastern Mediterranean University. Participants were Turkish and Turkish-Cypriot undergraduate university students who were all right handed, had normal hearing and either normal or corrected vision. Experimental tasks Word lists for the memory task Fifty-five discrete, highly frequent Turkish words that were two to three syllables in length were derived for the memory task from the word lists used in picture naming in a Turkish population (Raman, 2011; Raman & Weekes, 2005). No word was repeated in any of the lists, such that practice effects did not interfere with recall. A total of four word lists were prepared including three for the experimental and one for the practice trials. The experimental word lists consisted of 15 words, whereas the practice list included 10 words (fewer words were included in the practice list to reduce boredom and fatigue). Distraction task: Arithmetic filler task To eliminate the recency effect, a distractor task was employed. Participants performed an arithmetic filler task between the presentation of the word lists and the testing of recall. Participants were presented with 10 numbers randomly selected between 1 and 50 at a presentation rate of one number per second and asked to add three to each digit and report the sum orally. Marks were not lost for incorrect calculations or gained for accurately reporting the calculations. RT task The RT task was used as the secondary task in the measurement of the faculty of divided attention. The RT © 2014 International Union of Psychological Science
SEX DIFFERENCES IN MEMORY
from the onset of to the completion of each trial was recorded by a computer program with millisecond accuracy. For the RT task, four large boxes were displayed on the computer screen and in one of the boxes an asterisks randomly appeared. Each box corresponded to a different key on the keyboard and participants’ task was to press the correct corresponding key on the keyboard to the box in which the asterisks was appearing. Participants were instructed to perform this task as accurately and quickly as possible. Procedure Ethical approval was obtained from Eastern Mediterranean University, Department of Psychology, Research and Ethics Committee and all participants provided informed consent. Thereafter, participants practiced on all tasks including the memory task, distraction task and RT task under full attention, divided attention at encoding and divided at retrieval conditions (performed respectively only for the practice sessions). Following the practice session, the experimental session began. The total duration of testing for each participant was approximately 30 minutes, including the practice session and all testing was carried out in the afternoon. At the completion of the study, participants were thanked for their participation. The memory task was performed under three different attention conditions at encoding and retrieval, which included full attention, divided attention at encoding and divided attention at retrieval, respectively. The order of the conditions was counterbalanced across participants. To obtain participants’ baseline RT, the RT task was performed under full attention conditions at the beginning of each experimental session. Experimental sessions For all three experimental conditions (i.e. full attention, divided attention at encoding and divided attention at retrieval), the memory task began when the experimenter read aloud a list of 15 words at a rate of 4 seconds per word (encoding phase), followed by the performance of the distractor task. Thereafter, during the retrieval phase, participants verbally recalled as many of the words from the list in any order. For the full attention condition, participants performed the memory task without performing the secondary RT task. The RT task was performed for exactly 1 minute under full attention conditions prior to the completion of the memory task. For the divided attention at encoding condition, participants performed the RT task only during the encoding phase, whereas for the divided attention at retrieval condition the RT task was performed only during the retrieval phase. Participants were instructed to place equal emphasis on the RT and © 2014 International Union of Psychological Science
119
memory task and had approximately 2 minutes to verbally recall the words. The experiment ceased when the participant indicated that they could not remember any more words or when 2 minutes elapsed. RESULTS Performance on both the memory task (i.e. words recalled) and the secondary task (i.e. RTs) was measured under full attention and divided attention conditions and compared amongst the sexes. Therefore, any differences in the memory task and secondary task under the different attention conditions were the dependent variables with sex as the fixed factor. To determine the impact of reduced attention on the ability to encode and retrieve information, Cohen’s d effects sizes are further reported for males and females memory task performance during divided attention at encoding and retrieval. To assess secondary task costs, Cohen’s d is reported for sex-related differences in RT task performance during divided attention conditions compared to full attention conditions. Positive effect sizes indicate larger costs (i.e. greater decrement in RT task performance during divided attention conditions in comparison to the full attention condition) for males than females; negative effect sizes indicate the reverse. An alpha level of .05 was used for all the statistical inferential tests. A 2 (sex: male, female) × 3 (attention condition: full attention, divided attention at encoding and divided attention at retrieval) mixed design univariate analysis of variance (ANOVA) was run for both the recall task and RT task. Reaction time (RT) The 2 × 3 ANOVA results revealed a significant main effect for attention condition, F(1, 142) = 304.34, p < .001, ηp2 = .683, such that RTs were significantly shorter under the full attention condition (M = 743.37, SD = 118.54) than the divided attention at encoding (M = 1033.01, SD = 263.21) and divided attention at retrieval condition (M = 1243.67, SD = 292.75), p < .001. RTs were also significantly shorter under the divided attention at encoding than the divided attention at retrieval condition (p < .001). Furthermore, there was a significant main effect for sex, F(1, 142) = 7.34, p = .008, ηp2 = .050, indicating that overall females (M = 962.86, SD = 186.50) had faster RTs than males (M = 1047.54, SD = 186.62). The interaction between sex and attention condition was also significant, F(1, 142) = 3.32, p = .037, ηp2 = .023 for RT task performance. The interaction indicated that the sex differences in full attention RTs (d = 0.41) were more pronounced during the divided attention at retrieval condition (d = 0.51) than the divided attention at encoding condition (d = 0.23).
120
˘ SEÇER AND YILMAZOGULLARI
TABLE 1 Word recall (#correct) and reaction time (RTs; ms) in males and females under full attention and divided attention at encoding and retrieval. Means (SD)
Sex
Males M (SD)
Full attention Word recall 6.56 (1.88)* Secondary task RT 766.49 (136.88)* Divided attention at encoding Word recall 4.01 (1.59)* Secondary task RT 1062.71 (290.04) Divided attention at retrieval Word recall 4.90 (1.68) Secondary task RT 1313.43 (337.86)*
Females M (SD) 7.31 (1.98)* 718.57 (89.57)* 5.01 (1.77)* 1001.17 (228.86) 5.05 (1.75) 1168.85 (213.17)*
*p < .05.
Word recall The 2 × 3 ANOVA results revealed a significant main effect for sex, F(1, 142) = 8.21, p = .005, ηp2 = .055, indicating that overall females (M = 5.79, SD = 1.2) recalled more words than males (M = 5.16, SD = 1.29). Furthermore, a significant main effect for attention condition was found, F(1, 142) = 110.85, p < .001, ηp2 = .440, indicating that participants significantly recalled a greater number of words under the full attention condition (M = 6.94, SD = 1.91) than the divided attention at encoding (M = 4.51, SD = 1.67), p < .001, and the divided attention at retrieval condition (M = 4.98, SD = 0.1.67), p < .001. Word recall was also significantly higher in the divided attention at retrieval condition than the divided attention at encoding condition (p = .008). Furthermore, there was a significant interaction between sex and attention condition, F(1, 142) = 3.14, p = .043, ηp2 = .022. Females significantly recalled a greater number of words than males under the full attention (d = 0.38) and the divided attention at encoding condition (d = 0.59) but not the divided attention at retrieval condition (d = 0.09; see Table 1). This differential impact of divided attention on the sex differences in recall appears to be due to a larger negative impact of divided attention during encoding for males than females relative to the full attention condition. Specifically, males’ recall was significantly worse during divided attention at encoding (d = 1.46) than at retrieval (d = 0.93), whereas females’ reduction in performance was more similar between divided attention at encoding (d = 1.22) and at retrieval (d = 1.20). DISCUSSION This study examined sex differences in memory in light of the attentional resources framework (Craik & Byrd, 1982). It was expected that females would have a higher level of word recall under the following conditions: full attention, divided attention at encoding and
divided attention at retrieval. It was further expected that if sex differences in word recall reflect reductions in the available pool of attentional resources, then males would have larger secondary task costs at encoding and retrieval than females (i.e. longer RT performance in the divided attention conditions compared to the full attention condition). These expectations were partially supported. Findings of this study showed that females recalled a greater number of words in the full attention condition compared to males. Although both males and females experienced a decrease in word recall during divided attention conditions compared to full attention, females still recalled a greater number of words than males under divided attention at encoding but not divided attention at retrieval. That is, males’ drop in recall during divided attention at encoding was more severe than their drop in recall at retrieval compared to full attention, whereas females’ drop in recall during divided attention at encoding and retrieval compared to full attention was comparable. Such findings suggest that the sex differences in recall may be due to a greater effect of reduced attention during encoding than retrieval for males. With regard to the secondary RT task, females had shorter RTs than males during full attention. Females also had shorter RTs than males during divided at retrieval but not encoding when compared to full attention. Males, therefore, had larger secondary task costs (i.e. longer RTs) than females during divided attention at retrieval but not encoding. The current pattern of results suggests that males and females may differentially manage the performance of two concurrent tasks (i.e. the memory and secondary RT task). Research shows that concurrent tasks compete for a limited resource: attention (Barrouillet, Bernardin, & Camos, 2004; Barrouillet & Camos, 2012). When attention is switched away from a particular task (e.g. memory task) a decline in performance for that task begins (e.g. memory traces decline), yet can be refreshed before being completely lost by refocusing attention on that task (Barrouillet et al., 2004). As a consequence, attention is switched between tasks and can lead to a tradeoff between the two activities. Although participants in this study were requested to place equal emphasis on both tasks, it may be that participants did not confirm to this request. Therefore, males attended more to the secondary task during divided attention at encoding thereby improving their RT performance compared to females but reducing their ability to attend to the words resulting in worse recall. During divided attention at retrieval, however, males compensate for their relatively poor attention during encoding (reflected in their lower rates of word recall in the divided attention at encoding condition) by spending more time conducting a controlled search of memory that improved their recall, but at the expense of the secondary task (thereby resulting in longer RTs than females). Such findings indicate that © 2014 International Union of Psychological Science
SEX DIFFERENCES IN MEMORY
males and females may differentially manage the tradeoff between the memory and secondary RT task. Future research using a task emphasis manipulation is warranted to confirm this proposition. With regard to sex differences in word recall, the current findings are in line with past studies that show that females compared to males have superior word recall because they encode information more effectively (Guillem & Mograss, 2005; Krueger & Salthouse, 2010; Meyers-Levy & Maheswaran, 1991). To extend research in this area, this study aimed to determine whether males’ reduced ability to encode words effectively could be accounted for by a reduction in their attentional resources compared to females. In line with past research (Anderson, 1999), this study expected larger secondary task costs (i.e. longer RTs during divided attention conditions compared to full attention) at encoding and retrieval for males than females. This study indicated larger secondary task costs (i.e. longer RTs) for males than females during divided attention at retrieval but not at encoding. Therefore, expectations regarding secondary task costs were partially supported. Such findings suggest that reductions in attention may account for sex differences in word recall. Males compared to females’ may have a reduction in their pool of attentional resources, which may yield difficulties for males to perform controlled processes mainly during encoding (e.g. elaborative encoding). However, the larger secondary task costs at retrieval for males may simply be associated with increased response production costs rather than a reduction in attention (Craik et al., 1996). This therefore warrants the need for further research. According to the environmental support theory (Craik, 1983), memory tasks that provide environmental cues (e.g. recognition tasks) are easier to perform since they require less self-initiated processes that are resource demanding, as in free recall and cued recall tasks. As a result, any recall differences due to reductions in attention should be compensated by recognition tasks. Findings of Herlitz et al. (1997), however, showed that females recalled more words than males when tested with a free recall task, cued recall task and a recognition task. To clarify whether increased secondary task costs reflect production costs or a reduction in attention, future studies could employ a response conflict task. If males’ RTs during this task are slower or do not differ from their RTs in the full attention condition then increased RTs during retrieval are less likely to be accounted for by response production costs (Craik et al., 1996).This would strengthen the argument that sex-related differences in attention do exist. Future research is therefore needed to examine sex-related differences in attentional resources. The current results further reveal that both word recall was greater and RT scores were slower when attention was divided at retrieval than encoding. A possible limitation could be that the time allowed to perform the RT task © 2014 International Union of Psychological Science
121
across the conditions (i.e. 1 minute for the full attention and divided attention at encoding, and 2 minutes for the divided attention at retrieval) was not equivalent. However, past studies (e.g. Craik et al., 1996; Naveh-Benjamin et al., 2006) indicate that divided attention more negatively impacts recall when implemented during encoding rather than retrieval. Therefore, a decrease in attentional resources at the time of encoding affects word recall. Although word recall is spared when attention is divided at retrieval reductions in attention are manifested by an increase in secondary task performance. In line with this, results of this study also show that for both sexes word recall was best under full attention conditions and worst under divided attention at encoding and RTs were faster under full attention conditions and slowest under the divided attention at retrieval condition, replicating those of past research (i.e. Anderson, 1999; Craik et al., 1996) that show a differential effect of divided attention on encoding and retrieval processes. Such explanations also account for the current findings showing no sex differences in word recall during divided attention at retrieval. Furthermore, it is important to note that the power to detect sex-related differences in RT costs when attention was divided at encoding was low (.07). This could account for the non-significant secondary task cost findings during divided attention at encoding. A larger sample size may reveal sex-related differences in attentional resources. Overall, the current findings show that females outperformed males in the number of words that were remembered under both full attention and divided attention at encoding conditions. Females also had shorter RTs than males when attention was divided at retrieval but not encoding. These findings suggest that males and females may differentially manage the tradeoff between the memory and secondary RT task. Furthermore, secondary task costs were larger for males than females when attention was divided at retrieval. This finding suggests that there may be a reduction in the pool of attentional resources retained by males. Future research is however needed to verify these findings. Further research is also required to determine whether sex-related differences in word recall could be accounted for by sex-related differences in the cognitive control of attention. This could be examined by employing the divided attention paradigm and varying task emphasis for the primary and secondary task under three conditions, that is, primary task emphasis, secondary task emphasis, equal emphasis between the primary and secondary task (Craik et al., 1996). Any sex-related differences in RT costs under task emphasis conditions during encoding would suggest sex differences in the ability to allocate necessary attentional resources to memory tasks effectively. Manuscript received December 2013 Revised manuscript accepted October 2014 First published online November 2014
122
˘ SEÇER AND YILMAZOGULLARI
REFERENCES Anderson, N. D. (1999). The attentional demands of encoding and retrieval in younger and older adults: 2 Evidence from secondary task reaction time distributions. Psychology and Aging, 14(4), 645–655. Anderson, N. D., Craik, F. I. M., & Naveh-Benjamin, M. (1998). The attentional demands of encoding and retrieval in younger and older adults: 1. Evidence from divided attention costs. Psychology and Aging, 13(3), 405–423. Barrouillet, P., Bernardin, S., & Camos, V. (2004). Time constraints and resource sharing in adults’ working memory spans. Journal of Experimental Psychology: General, 133(1), 83–100. Barrouillet, P., & Camos, V. (2012). As time goes by: Temporal constraints in working memory. Current Directions in Psychological Science, 21(6), 413–419. Craik, F. I. M. (1983). On the transfer of information from temporary to permanent memory. Philosophical Transactions of the Royal Society of London, Series B, 302, 341–359. Craik, F. I. M., & Byrd, M. (1982). Aging and cognitive deficits: The role of attentional resources. In F. I. M. Craik & S. Trehub (Eds.), Aging and cognitive processes (pp. 191–211). New York, NY: Plenum. Craik, F. I. M., Govoni, R., Naveh-Benjamin, M., & Anderson, N. D. (1996). The effect of divided attention on encoding and retrieval processes in human memory. Journal of Experimental Psychology: General, 125(2), 159–180. Guillem, F., & Mograss, M. (2005). Gender differences in memory processing: Evidence from event-relate potential to faces. Brain and Cognition, 57, 84–92. Herlitz, A., Nilsson, L., & Backman, L. (1997). Gender differences in episodic memory. Memory and Cognition, 25(6), 801–811. Herlitz, A., & Rehnman, J. (2008). Sex differences in episodic memory. Current Directions in Psychological Science, 17(1), 52–56. Herlitz, A., & Yonker, J. E. (2002). Sex differences in episodic memory: The influence of intelligence. Journal of Clinical and Experimental Neuropsychology, 24(1), 107–114.
Krueger, L. E., & Salthouse, T. A. (2010). Differences in acquisition, not retention, largely contribute to sex difference in multitrial word recall performance. Personality and Individual Differences, 49, 768–772. Larsson, M., Lovden, M., & Nilsson, L. (2003). Sex differences in recollective experience for olfactory and verbal information. Acta Psychologica, 112, 89–103. Laws, K. R. (2004). Sex differences in lexical size across semantic categories. Personality and Individual Differences, 36, 23–32. Loven, J., Herlitz, A., & Rehnman, J. (2011). Women’s own-gender bias in face recognition memory: The role of attention at encoding. Experimental Psychology, 58(4), 333–340. Meyers-Levy, J., & Maheswaran, D. (1991). Exploring differences in males and females processing strategies. Journal of Consumer Research, 18, 63–70. Naveh-Benjamin, M., Kilb, A., & Fisher, T. (2006). Concurrent task effects on memory encoding and retrieval: Further support for an asymmetry. Memory and Cognition, 34(1), 90–101. Nyberg, L., Habib, R., & Herlitz, A. (2000). Brain activation during episodic memory retrieval: Sex differences. Acta Psychologica, 105, 181–194. Palmer, M. A., Brewer, A., & Horry, R. (2013). Understanding gender bias in face recognition: Effects of divided attention at encoding. Acta Psychologica, 142, 362–369. Park, D. C., Smith, A. D., Dudley, W. N., & Lafronza, V. N. (1989). Effects of age and a divided attention task presented during encoding and retrieval on memory. Journal of Experimental Psychology: Learning, Memory and Cognition, 15(6), 1185–1191. Raman, I. (2011). The role of age of acquisition in picture and word naming in dyslexic adults. British Journal of Psychology, 102, 328–339. Raman, I., & Weekes, B. S. (2005). Acquired dyslexia in a Turkish-English speaker. Annals of Dyslexia, 55(1), 79–104.
© 2014 International Union of Psychological Science
