International Journal of Neuroscience
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Time-of-Day-Induced Priming Effects on Verbal and Nonverbal Dichotic Tasks in Male and Female Adult Subjects L. L. Morton, M. J. Wojtowicz, N. H. Williams & J. R. Kershner To cite this article: L. L. Morton, M. J. Wojtowicz, N. H. Williams & J. R. Kershner (1992) Time-of-Day-Induced Priming Effects on Verbal and Nonverbal Dichotic Tasks in Male and Female Adult Subjects, International Journal of Neuroscience, 64:1-4, 83-96, DOI: 10.3109/00207459209000535 To link to this article: http://dx.doi.org/10.3109/00207459209000535
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Intern. J . Neuroscience, 1992, Vol. 64, pp. 83-96 Reprints available directly from the publisher Photocopying permitted by license only
0 1992 Gordon and Breach Science Publishers S . A . Printed in the United States of America
TIME-OF-DAY-INDUCED PRIMING EFFECTS ON VERBAL AND NONVERBAL DICHOTIC TASKS IN MALE AND FEMALE ADULT SUBJECTS L. L. MORTON, M. J. WOJTOWICZ and N. H. WILLIAMS The University of Windsor, Faculty of Education, 401 Sunset Avenue, Windsor, Ontario, Canada N9B 3P4
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J. R. KERSHNER Ontario Institute f o r Studies in Education, University of Toronto (Received August 27, 1991) Normal adults (32 males and 32 females) were tested for time-of-day related shifts in laterality and priming on two dichotic listening tasks using consonant-vowel combinations (CVs) and musical melodies. The predicted time-of-day effect on melodies was due to males showing low report in the morning, but not the afternoon, suggesting increased right hemisphere involvement in the afternoon. A time-ofday-induced priming effect on the laterality index for CVs differentiated males and females. Males tested morning-first were more lateralized than females, who in turn were more lateralized when tested afternoon-first. A time-of-day-induced priming effect on the laterality index for music indicated those tested afternoon-first showed an overall left ear advantage (LEA), whereas those tested morning-first showed an overall right ear advantage (REA). On raw music scores a sex-linked, time-of-day-induced priming effect was due to the prior presentation of CVs-that is, cognitive priming. Other priming effects on music were evident for order of stimulus presentation and order of ear attended. Implications for theory, research and pedagogy are discussed.
Keywords: Time-of-day; circadian rhythms; dichotic listening; music; priming effects; neuropsychology .
In dichotic listening two different messages are presented simultaneously-one to each ear-and subjects typically show a robust right ear advantage (REA) in reporting verbal stimuli (Kimura, 1961, 1967) and a left ear advantage (LEA) for nonverbal stimuli like music (Kimura, 1967). This processing difference is logically linked to the predominantly verbal and musical abilities of the left and right hemispheres, respectively, and structurally linked to the greater number of contralateral neural connections between ears and hemispheres. Thus, the ear advantage reflects the principal involvement of the contralateral hemisphere. Or, the ear advantage may reflect the more engaged hemisphere as a result of contralateral attentional biases (Kinsbourne, 1975). In either model a differential shift in performance reflects differential hemisphere functioning. This makes the dichotic technique valuable for examining shifts in hemisphere function. Folkard (1979) has hypothesized a normal circadian based shift from more involved left hemisphere processing in the morning to more involved right hemisphere processing in the afternoon. Thus, some tasks (i.e., left-hemisphere-linked tasks like verbal processing) could be performed better in the morning while other tasks (i.e., right-hemisphere-linked tasks like music processing) could be performed better in Please address correspondence to: Dr. L. L. Morton, The University of Windsor, Faculty of Education, 401 Sunset Avenue, Windsor, Ontario, Canada, N9B3P4
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the afternoon. This speculation is consistent with studies showing enhanced phonologically-related processing in the morning (Blake, 1967, Baddeley, Hatter, Scott and Snashall, 1970; Folkard, 1979)-presumably more left hemisphere oriented tasks (Beaton, 198S)-and studies showing enhanced visual processing in the afternoon (Lavie, 1980; Mackenberg, Broverman, Vogel and Klaiber, 1974; Morton, 1986; Morton and Kershner, 198S)-presumably more right hemisphere oriented tasks (Beaton, 1985). Such shifts, from more left hemisphere processing in the morning to more right hemisphere processing in the afternoon are potentially detectable on a dichotic task in several ways: (1) a lower right ear report in the afternoon (due to reduced left hemisphere involvement), (2) a greater left ear report in the afternoon (due to greater right hemisphere involvement), (3) a change in laterality as indicated by differences between right ear and left ear report, with a greater REA in the morning for left hemisphere tasks (e.g., verbal tasks) and a greater LEA in the afternoon for right hemisphere tasks (e.g., musical tasks), and (4) a bilateral decline between morning and afternoon testing for tasks purportedly performed by the left hemisphere (e.g., verbal tasks), or, a bilateral increase for tasks purportedly performed by the right hemisphere (e.g., music tasks). However, dichotic performance may also be subject to priming influences (i.e., prior situational factors) which in turn could be affected by time-of-day. Priming in children occurs with such factors as (1) directions to attend left first or right first (Hiscock and Kinsbourne, 1980; Hiscock, Kinsbourne, Caplan and Swanson, 1979; Hiscock and Bergstrom, 1982; Kershner and Morton, 1990) (i.e., an attentional priming effect), and (2) the prior exposure to different stimuli such as music (Morton, Kershner and Siegel, 1990) or CVs and digits (Morton and Siegel, 1991) (i.e., cognitive priming effects). In addition, altering the time of day when testing first occurs influences subsequent performance (Morton and Kershner, in press) (i.e., time-of-daylinked priming effects). To illustrate, Morton and Kershner (in press) noted no differences between reading disabled and control subjects in afternoon testing whereas there were differences in morning testing with the normal-achieving being more proficient. In a second experiment involving normal-achieving children the enhanced performance in the morning was seen to be linked to a priming effect-subjects directed to attend right-ear-first in the morning showed higher overall report for dichotic digits. The opposite pattern was evident in the afternoon. Being directed rightear-first in the morning may preferentially activate the left hemisphere leading to overall better processing. In the afternoon, it seems necessary to activate the right hemisphere (by being directed left-ear-first) in order to obtain the higher results. In view of priming effects and this intriguing link between time-of-day and priming with children (Morton and Kershner, in press) a consideration of order variables would appear to be warranted in dichotic studies, especially when time-of-day effects are a focus. The present study was designed to examine circadian shifts in hemispheric involvement using the dichotic listening technique and tasks linked to the left hemisphere (processing CVs) and the right hemisphere (processing musical melodies). The research design allowed for a consideration of (1) attentional priming (i.e., the effect of being directed to attend left first versus right first), (2) cognitive priming (i.e., the effect of being exposed to the CVs first versus the music first) and (3) time-of-day priming (i.e., the effect of attending in the morning first versus the afternoon first. Incorporating these priming factors in one study allowed for consideration of interesting potential interrelationships. The principal prediction of the study, based on Folkard’s (1979) suggestion of a circadian based shift to more right hemisphere involvement in the afternoon, was
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that subjects would show a laterality shift with relatively more left hemisphere processing in the morning and relatively more right hemisphere processing in the afternoon. Specifically, it was predicted that performance on a left hemisphere task (i.e., phonological processing of CVs) would decline over the course of the day (as measured by a reduced REA, reduced right ear report, or reduced bilateral report) indicative of left hemisphere decline, whereas performance on a right hemisphere task (i.e., processing musical melodies) would improve over the course of the day (as measured by an increased LEA, increased left ear report, or increased bilateral report), indicative of right hemisphere ascendancy. A second more general prediction, based on previous findings with children (Morton and Kershner, in press), was that adult subjects, like children, would show timeof-day linked priming effects, particularly in the morning.
METHOD Subjects
Subjects were university students and recent graduates, in the age range 20-55 years. There were 32 males (27 right-handed, 5 left-handed) and 32 females (26 righthanded, 6 left-handed). The Edinburgh Inventory (Oldfield, 1971) was used to determine subject’s hand preference. Subjects were within the high-average to the aboveaverage range on the WAIS-R vocabulary subtest (scaled score mean = 13.38, SD = 2.79; males, mean = 13.50, SD = 2.79; and females, mean = 13.25, SD = 3.03), and on the WAIS-R block design subtest (scaled score mean = 12.97, SD = 2.23; males, mean = 13.31, SD = 2.16, and females, mean = 12.63, SD = 2.28). Hearing was tested with a Beltone Model 119 Audiometer, set at 25 db, and only subjects with normal hearing, 1000 Hz-8000 Hz range, were selected. Materials and Apparatus
For the dichotic music task, 10 sets of target melodies, 5 seconds in duration, were employed. Two of the melodies were presented, one to each ear, followed, after a four second delay, by four test melodies. These four test melodies were made up of the melody heard in the right ear and the melody heard in the left ear and two extra melodies. Each of these four melodies was separated by a 2 second gap. The CV tape was composed of the six stop consonants paired with a vowel /a/. Each CV was paired once with every other CV for a total of 30 pairs of monosyllables which were presented spaced 7 seconds apart. The tape was produced by Auditec of St. Louis (Rand H-No Delay). The tapes were presented on a Realistic Stereo Dual Cassette Tape Deck SCT-74 connected to a Realistic Digital Synthesized Stereo Receiver STA-2 150. Subjects listened to the tapes with Realistic pro-60 stereo headphones. Digital skin temperature was recorded on a Temp SC201T digital skin temperature monitor. Procedure
For the dichotic tasks an ordered-report, focused-attention paradigm was used. Counterbalancing was implemented for stimulus presented first (CVs first, Music first), for time of first testing (morning first, afternoon first), and for direction attended
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first (directed left first, directed right first). This controlled for practice effects and monitored for various order or priming effects. All subjects were directed to attend to the left earphone. When subjects were directed to attend left, the left earphone would be on the left ear. When subjects were directed to attend right, the left earphone would be on the right ear. This counterbalancing procedure was employed to control for differences in the signal-to-noise ratio between channels. Three warm-up trials were given prior to testing. Continual reminders were given during testing to ensure that subjects were attending as directed. The two listening tasks were heard consecutively, with only a short pause to change tapes and give instructions for the second task. For the CV task, a sheet displaying the CVs (ba, da, ga, ka, pa, and ta) was provided for reference. Subjects were instructed to direct attention to one ear for 30 trials, then switch earphones and direct attention to the other ear for 30 trials. For the dichotic music task the two target melodies were presented followed by four melodies made up of the melody heard in the right ear and the melody heard in the left ear and two extra melodies. The subjects had to identify the target melody by specifying whether it was the first, second, third or fourth melody. These melodies were played in succession with the same set of melodies presented for left ear and right ear trials. Prior to the tasks a Velcro band with an attached temperature probe was affixed to the subject’s left index finger to monitor body temperature during the music tasks. The music task (approximately 20 minutes in duration) provided ample opportunity for the skin temperature to stabilize. The temperature was recorded prior to switching earphones and attending to the other ear. The entire data collection process took a total of 90 minutes per subject. In an attempt to accommodate students’ varied schedules the two test sessions were spaced randomly over a period of several weeks. To ensure that the different test-retest intervals did not influence performance comparisons were made between subjects who had brief test-retest intervals (1-3 days) with those who had longer test-retest intervals (4-21 days) on all dependent variables. There were no differences between the two groups on any of the dependent measures ( p > .OS), and neither did the test-retest interval itself correlate with any of the dependent measures ( p > .05), thus, analyses of variance rather than analyses of covariance were utilized for analysis.
RESULTS Preliminary Analyses Preliminary analyses indicated there were no differences between the two handedness groups. Skin Temperature Digital skin temperature in the afternoon (mean = 32.46 degrees Celsius, SD = 4.46) was significantly higher than the morning (mean = 31.64 degrees Celsius, SD = 4.49), t (63) = 2.95, p < .01, supporting the claim for higher arousal levels in the afternoon (Colquhoun, 1971). Laterulity Indices The results were analyzed using a standard laterality index ((R, - L , / R , + L,) X 100) after Marshall, Caplan, and Holmes (1975). In this index R, = right ear correct report, L, = left ear correct report. Using this index a positive number indicates a REA while a negative number indicates a LEA.
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CV Index A five-way analysis of variance (ANOVA) was computed for the laterality index for CVs with Sex (male, female), Time-Tested-First (morning, afternoon), Ear-Attended-First (left, right), Stimulus-Presented First (CVs, Music) and Time-of-Day (morning, afternoon) as the independent variables. Time-of-Day was the only within-subjects variable and was treated as a repeated measure. There were no main effects, but there was a significant Sex by Time-Tested-First two-way interaction, F(1, 48) = 6.70, p < .025, indicating a time-of-day priming effect (see Figure la). Tests for simple effects (Winer, 1971) indicated males showed higher laterality scores (mean = 22.51) than females (mean = 4.88) when tested moming-first, t(30) = 2.29, p < .05. Females showed higher laterality scores (mean = 15.95) when tested afternoon-first, t(30) = 2.23, p < .05. Means and standard deviations are reported in Table 1. Music Index A similar five-way ANOVA (Sex by Time-Tested-First by Ear-Attended-First by Stimulus-Presented First by Time-of-Day) was computed for the laterality index for music. There were two main effects and one two-way interaction. The main effect for Time-Tested-First, F(1, 48) = 7.53, p < .01, indicated a timeof-day priming effect for both male and female subjects. In effect, there was an overall REA for subjects tested morning-first (mean = 1.44) and a LEA for subjects tested afternoon-first (mean = -4.19). The main effect for Ear-Attended-First, F( 1, 48) = 7.05, p < .025, was due to a REA when directed to attend to the left ear first (mean = 1.35) and a LEA when directed to attend to the right ear first (mean = -4.1). The significant Sex by Stimulus-Presented-First, two-way interaction, F(1, 48) = 6.45, p < .025, indicated a cognitive priming effect (see Figure lb). Tests for simple effects revealed that males showed a LEA (mean = -6.01) when the CVs preceded the music task but a REA when the music task was first (mean = 1.96), t(30) = 2.31, p < .05. Females showed an opposite pattern. Means and standard deviations are reported in Table 2.
Raw Scores The results were subsequently analyzed using the raw scores for the left ear and right ear report for CVs and music in an attempt to explicate the mechanics of the laterality effects. CVs A six-way ANOVA was computed for CVs with Sex (male, female), TimeTested-First (morning, afternoon), Ear-Attended-First (left, right), Stimulus-Presented First (CVs, music) Ear (left, right) and Time-of-Day (morning, afternoon) as the independent variables. Ear and Time-of-Day were within-subjects variables treated as repeated measures. There was a main effect for Ear, F( 1, 48) = 3 1.60, p < .001, which was qualified by a significant Sex by Time-Tested-First by Ear three-way interaction, F( 1, 48) = 8.07, p < .01. Tests for simple effects indicated that males showed depressed left ear scores (mean = 10.1) when tested morning-first compared to females (mean = 13.16), t(30) = 2.14, p < .05, and compared to right ear report (mean = 16.22), t( 15) = 3.49, p < .01. Conversely, females showed enhanced right ear report (mean = 16.81) when tested afternoon-first compared to males (mean = 13.88), t(30) = 2.01, p = .05, and compared to left ear report (mean = 12.19), t(l5) = 4.56, p < .01. Apparently, males show reduced left ear report when primed in the morning which explains the greater laterality score for males tested in the morning first; females show enhanced right ear report when primed in the afternoon which explains
L.L. MORTON rt a / .
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Time-Of-Day Priming Effect On CVs
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5
0 Morning
A
Afternoon
Time-Of-Day Tested First
Cognitive Priming Effect On Music
M U
8
i
-8
B
__
cvs
,
__
Music
Stimulus Tested First
AGURE 1 Laterality index scores for (a) CVs for males and females tested morning-first and afternoon-first showing greater laterality for males tested morning-first and for females tested afternoon-first and (b) music for males and females when CVs are tested first and music is tested first showing the left ear advantage for males when the CVs are presented first and the right ear advantage when the music is first
the greater laterality score for females tested in the afternoon first. Means and standard deviations for the raw scores are reported in Table 3 .
Music A similar six-way ANOVA (Sex by Time-Tested-First by Ear-Attended-First by Stimulus-Presented First by Ear by Time-of-Day) was computed for music stimuli. A main effect along with two-way, three-way and four-way interactions indicated complex effects with respect to musical processing. The main effect for Ear-At-
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TABLE 1 Means and Standard Deviations for the Laterality Index for CVs For Males and Females When Directed To Attend In The Morning First And When Directed to Attend In The Afternoon First Males
Time-Tested-First Morning-First Afternoon-First
Females
Mean
SD
Mean
SD
22.51 10.16
27.11 16.73
4.89 15.95
14.55 13.44
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Note. The laterality index ( ( R , - L,/R, (1975).
+ L,)
X
100) was adopted from Marshall, Caplan and Holmes
tended-First, F(1, 48) = 4.15, p < .05, was qualified by a significant Ear-AttendedFirst by Ear two-way interaction, F( 1, 48) = 12.06, p < .001. This indicates a right hemisphere priming effect which benefits subsequent left hemisphere/right ear performance (see Figure 2a). Tests for simple effects indicated that right ear report for music was depressed (mean = 7.67) (1) when compared to left ear report (mean = 8.16) when subjects were directed to attend to the right ear first, t(3I) = 3.04, p < .01, and (2) when compared to subjects directed to attend to the left ear first (mean TABLE 2 Means and Standard Deviations for the Laterality Index For Music For Males and Females When Tested Using CVs First and When Tested Using Musical Stimuli First Males
Stimuli-Tested-First CVs-First Music-First
Females
Mean
SD
Mean
SD
-6.01 1.96
12.85 5.05
0.50 -1.95
5.67 9.35
Note. The laterality index ((R, - L,/R,
+ L,) X
100) was adopted from Marshall, Caplan and Holmes
( 1975).
TABLE 3 Means and Standard Deviations for the Raw Scores For CVs For Left Ear Report and Right Ear Report For Males and Females When Directed To Attend In The Morning First And When Directed To Attend In The Afternoon First Males
Left Ear Time-Tested-First Morning-First Afternoon-First Right Ear Time-Tested-First Morning-First Afternoon-First
Fenfales
Mean
SD
Mean
SD
10.09 11.59
4.12 4.47
13.16 12.18
3.96 3.01
16.22 13.88
5.74 4.23
14.41 16.81
3.51 4.05
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Right Hemisphere Priming Effects
1
Right First
Left First
1
u
; 8.5 e
r
C
8
0
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r
r e
7.5
C
t 7
Left
A
Right
Ear Attended
Time- Of -Day Effect
Morning
R
Afternoon
Time-Of-Day For Doing The Music Task
FII left first and when directed right first showing tne ennancea nght ear report when directed left first (a right hemisphere priming effect) and (b) males and females in morning and afternoon tests showing the low morning performance for males (a time-of-day effect)
= 8.67), t(62) = 2.71, p < .01, Attending to the left ear first acts as a prime (perhaps a right hemisphere prime) that facilitates subsequent attending to the right ear. The Sex by Time-of-Day interaction, F(1,48) = 4.07, p < .05 indicates a timeof-day effect for males (see Figure 2b). Tests for simple effects indicated that males had reduced report in the morning (mean = 7.67) compared to the afternoon (mean = 8 . 2 3 , t(31) = 2.02, p < .05. Females showed high performance in both morning
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TABLE 4 Left Ear Report Means and Standard Deviations For Music For Males and Females In The Morning And Afternoon For Two Order Variables-Stimulus Presented First and Time-Tested First Males Stimulus First CVs-First Time-Tes ted-First Morning-First
M
SD Afternoon-First
M
SD
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Music-First Morning-First
M
SD Afternoon-First
M
SD
Females
Morning
Afternoon
Morning
Afternoon
6.88 1.46 8.00 1.93
7.87 0.99 7.63 1.85
8.38 1.41 8.88 1.25
8.63 1.19 8.50 1.20
7.13 2.17 9.13 0.99
8.63 1.19 8.75 1.28
7.75 1.98 9.00 0.76
8.75 1.39 8.25 1.39
(mean = 8.5) and afternoon (mean = 8.44) testings. Apparently, males are musically disadvantaged in the morning. A practice effect was evident in the Time-of-Day by Time-Tested-First two-way interaction, F( 1, 48) = 16.68, p < .001. Subjects tested first in the morning (mean = 7.7) showed enhanced performance when subsequently tested in the afternoon (mean = 8.61), r(31) = 3.44, p < .01, and subjects tested first in the afternoon (mean = 8.08) showed enhanced performance when subsequently tested in the morning (mean = 8.47), t(31) = 2.16, p < .05. Thus, a practice effect exists for the music stimuli only, and regardless of time tested first. The two two-way interactions (Sex by Stimulus-Presented-First, F( 1, 48) = 6.32, p < .025, and Time-Tested-First by Ear, F(l, 48) = 12.06, p < .01) and the threeway interaction (Sex by Stimulus-Presented-First by Ear, F(1, 48) = 5.05,p < .05) are qualified by the four-way interaction (Sex by Stimulus-Presented-First by TimeTested-First by Ear, F(1, 48) = 3.90, p < .05). Simple effects tests revealed that in the morning-first condition males showed lower music report than females on the left ear (male mean = 7.38; female mean = 8 . 5 ) , t(14) = 2.22, p < .05, and the right ear (male mean 7.5; female mean = 8.75), t(14) = 2.27, p < .05, but only when the CVs were processed first. Figure 3a, which presents difference scores between males and females (i.e., female score minus male score) tested morning-first, portrays this interaction. The CVs are contributing to a priming bias which interferes with the information processing for musical stimuli of males only. There is a difference favoring females but only when the CVs are first. In the afternoon-first condition males showed the same pattern but only for the right ear report. As may be seen in Figure 3b, females have the advantage on music processing when the CVs are presented first, whereas males have the advantage (represented by the negative score) when the music is first. More specifically, males do better than females on the right ear report for music (male mean = 9.06; female mean = 7.68), t(14) = 2.21, p < .05, but only when there is no prior processing of CVs. When the CVs are processed first in the afternoon-first condition the right ear report of the males is still depressed (mean = 6.8), t(14) = 2.5, p < .05. Means and standard deviations are reported in Tables 4 and 5.
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TABLE 5 Right Ear Report Means and Standard Deviations For Music For Males and Females In The Morning And Afternoon For Two Order Variables-Stimulus Presented First and Time-Tested First Males Stimulus First CVs-First Time-Tested-First Morning-First Afternoon-First
M SD M
SD
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Music-First Morning-First Afternoon-First
M SD M
SD
Females
Morning
Afternoon
Morning
Afternoon
6.88 2.90 6.88 2.70
8. I3 0.99 6.75 2.12
8.50 0.93 8.88 1.36
9.00 0.76 8.25 1.17
7.50 2.00 9.00 1.31
9.13 0.84 9.13 0.99
8.63 1.77 8.00 2.00
8.75 1.39 7.38 1.85
DISCUSSION Right Hemisphere Processing In The Afternoon
On the raw scores for music there was a clear time-of-day effect wherein males showed reduced performance in the morning. Given the right hemisphere involvement in music processing (Gates and Bradshaw, 1977: Kimura, 1967) this effect is consistent with a depressed right hemisphere in the morning and provides support for Folkard’s (1979) contention that there may be a shift to more right hemisphere processing in the afternoon. In the present study the effect is clearly evident for males only. Thus, Folkard’s (1979) hypothesis apparently should be further explored in terms of sex and task variables. The predicted circadian shift in laterality was not directly supported by the laterality indices. Evidence for simple laterality shifts was precluded by the various priming effects which were influencing both CV report and music report. Priming Effects Time-of-day-linked priming influences Based on the performance of male children using a dichotic digits task (Morton and Kershner, in press) it had been predicted that adults would show similar time-linked attentional priming effects using different stimuli (i.e., CVs and melodies). The specific priming effect related to time-of-day and direction-attended-first was not directly evident. However, there were compelling, though complex, time-of-day-induced priming effects for CVs and music. A time-of-day induced priming effect was evident on the CV laterality index. Males were more lateralized than females but only when tested morning-first. It was as if the morning test setting primed the left hemisphere for males, manifested by a strong REA. This is consistent with previous findings with children (Morton and Kershner, in press) in which males were seen to perform better in the morning on a dichotic digits task, but only when the left hemisphere (attending right) was primed first. Moreover, that the effect in the present study continued to exist for subsequent afternoon testing over time intervals ranging from 1 to 21 days is consistent with Hiscock and Bergstrom’s (1982) report of a priming effect existing at least one week later.
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When the CV raw scores were analyzed it was apparent that the morning-first priming effect was caused by lower left ear report for males. Conversely, the afternoon-first priming effect for females was caused by increased right ear report. The reason for this sex difference is not clear. It would seem that males are more vulnerable to right hemisphere (left ear) depression as a result of morning-priming. On the other hand females seem to be more amenable to left hemisphere (right ear) engagement as a result of afternoon-priming. Male and female brains may follow different circadian rhythms for arousal or arousal-related hormones which impact upon hemisphere engagement patterns. These sex differences would warrant closer scrutiny in future time-of-day research. The laterality index for music revealed a clear time-of-day-induced priming effect. When subjects were tested morning-first they showed on overall REA on the music stimuli. However, subjects tested afternoon-first showed a LEA. The LEA is the expected effect for musical stimuli (Kimura, 1967). The fact that the LEA exists for subjects tested afternoon-first suggests that the afternoon testing primes the right hemisphere to process the music and this primed right hemisphere is preferentially engaged for subsequent morning testing also. Conversely, exposure to the music task morning-first appears to be a handicapping condition creating a processing bias to the potentially less preferred hemisphere. It would seem that it is not so much the time-of-testing which is important as the time of priming. These time-of-day-induced priming effects may be important for understanding maladaptive learning. It may be the case that time-locked experiences create persistent and longterm biases either facilitating or hindering subsequent learning. This could be a potentially fruitful area for future research. Finally, there was a time-of-day-induced cognitive priming effect for music. It was clear that the prior processing of CVs depressed performance for males on left ear report and right ear report when they were tested first in the morning (see Figure 3a). Furthermore, males were seen to show increased right ear report when there was no prior processing of CVs when the afternoon testing was first (see Figure 3b). Males seem to have a very effective right ear/left hemisphere ability or transcallosal ability, compared to females, for processing musical stimuli at the right ear if they are tested first in the afternoon, and if they are not exposed to CVs first. At the same time, males are seen to be quite vulnerable to situational priming factors such as time-of-day and cognitive precursors. Other priming influences Although these"other" priming effects were not predicted they are interesting and perhaps directive. On the laterality index for music there was a Sex by Stimulus-Presented-First interaction-a cognitive priming effect. The interaction was due to males showing a LEA on the musical stimuli but only when they processed CVs prior to the music. Females do not show this shift. It is as if the CVs prime the males for a LEA on music. Perhaps, the CV task creates a bias to the right ear (left hemisphere) for linguistic stimuli impeding a focus on the right ear for musical stimuli. In fact, an examination of the raw scores for each ear reveals that the prior processing of CVs depresses left ear report and right ear report in males on musical stimuli and that the right ear report is more depressed than the left ear report. This effect is evidence in the three-way interaction (Sex by Stimulus-Presented-First by Ear). Thus, the prior processing of CVs suggests a linguistic bias in males that interferes with subsequent processing of categorically different stimuli. Males may lack attentional flexibility for cognitively different stimuli or stimuli differentially processed by the left and right hemispheres.
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FIGURE 3 Difference scores (female minus male score) for melodies reported for left and right ear when CVs were presented first and when music was presented first in (a) the morning-first condition showing females did better than males when the CVS preceded the music task and (b) the afternoonfirst condition showing females did better than males on the right ear report (+ 1.7) when CVs preceded the music task, whereas, males did better than females (- I .4) when the music was first
An attentional priming effect was also evident on the raw scores for music. When subjects were directed to attend to the right ear first they showed depressed right ear report on music stimuli (see Figure 2a). When they were directed to attend to the left ear first their subsequent right ear report increased. High left ear report would be predictable given (1) the preferential access the left ear would have to the right hemisphere and (2) the right hemisphere’s lead in music processing. The fact that there is no difference when subjects are directed left first suggests an attentional
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priming effect or right hemisphere priming effect is operative whereby being directed left first activates the right hemisphere which remains activated to process the musical stimuli (1) directly at the left ear and (2) subsequently, ipsilaterally at the right ear, or across the corpus callosum to the left hemisphere and then to the right ear.
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Conclusions The predicted shift to greater right hemisphere processing in the afternoon was partially supported by male performance on the music task. This is an important finding and indicates the need to consider both the sex variable and different types of stimuli in future time-of-day research. Although complex, the time-of-day-induced priming effects are equally important. These priming effects raise important questions about research design, hemispheric functioning and learning sequences. ln terms of research design, neuropsychological researchers need to be aware of the potential influences of priming effects related to time-of-day , cognitive precursors, and attentional practices. As research studies which examine these variables begin to accumulate, patterns may emerge which would shed light on the rhythms of hemispheric functioning-rhythms that may be informationally driven (e.g., cognitive priming) as well as physiologically drive (e.g ., time-of-day-induced priming). Even information processing sequences may prove to be neuropsychologically important. In terms of learning sequences, one could speculate that the order of curriculum presentation could impact neuropsychologically upon subsequent performance. For example, in school, a music task prior to a reading task, or a spelling task prior to a music task-especially at critical times during the day-possibly could affect hemispheric engagement patterns. The present findings suggest this possibility exists. Obviously, it is premature to suggest educational implications but the possibility of short-term and long-term priming effects warrants continued investigation. Theoretically, these priming effects may be linked to the priming of procedural memory systems (Tulving, 1985; Tulving, Schacter and Stark, 1982) rather than the priming of semantic systems (Chiarello, Burgess, Richards and Pollock, 1990) in view of the extended time lag between priming and priming effect. The priming of procedural memory seems to extend quite readily over long time periods (Hiscock and Bergstrom, 1982; Tulving et al., 1982). Thus, these priming effects may reflect an important infrastructure of learning and learning set related to procedural memory systems. However, at this time, additional research is necessary to explicate fully the nature of these intriguing and potentially important priming effects.
REFERENCES Baddeley, A. D . , Hatter, J . E . , Scott, D . , & Snashall, A . (1970). Memory and time of day. Quarterly Journal of Experimental Psychology, 2 2 , 605-609. Beaton, A. (1985). Left side, right side: A review of laterality research. New Haven: Yale University Press. Blake, M. J . F. (1967). Time of day effects on performance in a range of tasks. Psychonomic Science, 9. 349-350. Chiarello, C. Burgess, C . , Richards, L. & Pollock, A . (1990). Semantic and associative priming in the cerebral hemispheres: Some words do, some words don’t . . . sometimes, some places. Brain and Language, 38, 75-104. Colquhoun, W. P. (197 1). Biological rhythms and human pe$ormance. London: Academic Press.
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Folkard, S. (1979). Time of day and level of processing. Memory and Cognirion, 7 , 247-252. Folkard, S. (1982). Circadian rhythms and human memory. In F. Brown and R Graeber (Eds.) Rhythmic aspects of behavior. Hillsdale, New Jersey: Lawrence Erlbaum, pp. 241-272. Gates, A., & Bradshaw, J. L. (1977). The role of the cerebral hemispheres in music. Bruin and Language, 4 , 403-431. Hiscock, M. & Bergstrom, K. J . (1982). The lengthy persistence of priming effects in dichotic listening. Neuropsychologia, 20, 43-53. Hiscock, M. & Kinsbourne, M. (1980). Asymmetries of selective listening and attention switching in children. Developmental Psychology, 16. 70-82. Hiscock, M., Kinsbuurne, M., Caplan, B. & Swanson, J. M. (1979). Auditory attention in hyperactive children: Effects of stimulant medication on dichotic listening performance. Journal of Abnormal Psychology, 88, 27-32. Hiscock, M. & Stewart, C. (1984). The effect of asymmetrically focused attention upon subsequent ear differences in dichotic listening. Neuropsychologia, 25, 507-5 17. Kershner, J. R. & Morton, L. L. (1990). Directed attention dichotic listening in reading disabled children: A test of four models of maladaptive lateralization. Neuropsyrhologia, 28, 181-198. Kimura, D. (1961). Cerebral dominance and the perception of verbal stimuli. Canadian Journal of Psychology, 15, 166-171. Kimura, D. (1967). Functional asymmetry of the brain in dichotic listening. Cortex, 3, 163- 178. Kinsbourne, M. (1975). The mechanism of hemispheric control of the lateral gradient of attention. In M. A. Rabbitt & S. Dornic (Eds.) Attenrion andpegormance V. London: Academic Press. Lavie, P. (1980). The search for cycles in mental performance from Lombard to Kleitman. Chronobiologia. 7 , 247-256. Mackenberg, E. J . , Broverman, D. M . , Vogel, W., & Kleiber, E. L. (1974). Morning-to-afternoon changes in cognitive performances and in the electroencephalogram. Journul of Educational Psychology, 66, 238-246. Morton, L. L. (1986). A single-subject study of the effects of time on task and time of day on productivity and achievement in a dysgraphic student. Canadian Journat for Exceptional Chitdren, 3 , 23-28. Morton, L. L. & Kershner, J . R. (1985). Time-of-day effects upon children's memory and analogical reasoning. The Alberta Journal of Educarional Research. 3 I , 26-34. Morton, L. L. & Kershner, J. R. (in press). Time-of-day effects on neuropsychological behaviors as measured by dichotic listening. International Journal of Neuroscience. Morton, L. L . , Kershner, J . R. & Siegel, L. S. (1990). The potential for therapeutic applications of music on problems related to memory and attention. The Journal of Music Therapy, 27. 195-208. Morton, L. L. & Siegel, L. S. (1991). Left ear dichotic listening performance on consonant-vowel combinations and digits in subtypcs of reading disabled children. Brain and Language, 40, 162180. Tulving, E. (1985). How many memory systems are there'? American Psychologist, 4 0 , 385-398. Tulving, E., Schacter, D. L. & Stark. H. A. (1982). Priming effects in word-fragment completion are independent of recognition memory. Journal of Experimental Psychology: Learning. Memory. and Cognition, 8. 336-342. Winer, B. J. (1971). Sratisrical principles in experimental design. New York: McCraw-Hill.
ISSN: 0020-7454 (Print) 1543-5245 (Online) Journal homepage: http://www.tandfonline.com/loi/ines20
Time-of-Day-Induced Priming Effects on Verbal and Nonverbal Dichotic Tasks in Male and Female Adult Subjects L. L. Morton, M. J. Wojtowicz, N. H. Williams & J. R. Kershner To cite this article: L. L. Morton, M. J. Wojtowicz, N. H. Williams & J. R. Kershner (1992) Time-of-Day-Induced Priming Effects on Verbal and Nonverbal Dichotic Tasks in Male and Female Adult Subjects, International Journal of Neuroscience, 64:1-4, 83-96, DOI: 10.3109/00207459209000535 To link to this article: http://dx.doi.org/10.3109/00207459209000535
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Intern. J . Neuroscience, 1992, Vol. 64, pp. 83-96 Reprints available directly from the publisher Photocopying permitted by license only
0 1992 Gordon and Breach Science Publishers S . A . Printed in the United States of America
TIME-OF-DAY-INDUCED PRIMING EFFECTS ON VERBAL AND NONVERBAL DICHOTIC TASKS IN MALE AND FEMALE ADULT SUBJECTS L. L. MORTON, M. J. WOJTOWICZ and N. H. WILLIAMS The University of Windsor, Faculty of Education, 401 Sunset Avenue, Windsor, Ontario, Canada N9B 3P4
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J. R. KERSHNER Ontario Institute f o r Studies in Education, University of Toronto (Received August 27, 1991) Normal adults (32 males and 32 females) were tested for time-of-day related shifts in laterality and priming on two dichotic listening tasks using consonant-vowel combinations (CVs) and musical melodies. The predicted time-of-day effect on melodies was due to males showing low report in the morning, but not the afternoon, suggesting increased right hemisphere involvement in the afternoon. A time-ofday-induced priming effect on the laterality index for CVs differentiated males and females. Males tested morning-first were more lateralized than females, who in turn were more lateralized when tested afternoon-first. A time-of-day-induced priming effect on the laterality index for music indicated those tested afternoon-first showed an overall left ear advantage (LEA), whereas those tested morning-first showed an overall right ear advantage (REA). On raw music scores a sex-linked, time-of-day-induced priming effect was due to the prior presentation of CVs-that is, cognitive priming. Other priming effects on music were evident for order of stimulus presentation and order of ear attended. Implications for theory, research and pedagogy are discussed.
Keywords: Time-of-day; circadian rhythms; dichotic listening; music; priming effects; neuropsychology .
In dichotic listening two different messages are presented simultaneously-one to each ear-and subjects typically show a robust right ear advantage (REA) in reporting verbal stimuli (Kimura, 1961, 1967) and a left ear advantage (LEA) for nonverbal stimuli like music (Kimura, 1967). This processing difference is logically linked to the predominantly verbal and musical abilities of the left and right hemispheres, respectively, and structurally linked to the greater number of contralateral neural connections between ears and hemispheres. Thus, the ear advantage reflects the principal involvement of the contralateral hemisphere. Or, the ear advantage may reflect the more engaged hemisphere as a result of contralateral attentional biases (Kinsbourne, 1975). In either model a differential shift in performance reflects differential hemisphere functioning. This makes the dichotic technique valuable for examining shifts in hemisphere function. Folkard (1979) has hypothesized a normal circadian based shift from more involved left hemisphere processing in the morning to more involved right hemisphere processing in the afternoon. Thus, some tasks (i.e., left-hemisphere-linked tasks like verbal processing) could be performed better in the morning while other tasks (i.e., right-hemisphere-linked tasks like music processing) could be performed better in Please address correspondence to: Dr. L. L. Morton, The University of Windsor, Faculty of Education, 401 Sunset Avenue, Windsor, Ontario, Canada, N9B3P4
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the afternoon. This speculation is consistent with studies showing enhanced phonologically-related processing in the morning (Blake, 1967, Baddeley, Hatter, Scott and Snashall, 1970; Folkard, 1979)-presumably more left hemisphere oriented tasks (Beaton, 198S)-and studies showing enhanced visual processing in the afternoon (Lavie, 1980; Mackenberg, Broverman, Vogel and Klaiber, 1974; Morton, 1986; Morton and Kershner, 198S)-presumably more right hemisphere oriented tasks (Beaton, 1985). Such shifts, from more left hemisphere processing in the morning to more right hemisphere processing in the afternoon are potentially detectable on a dichotic task in several ways: (1) a lower right ear report in the afternoon (due to reduced left hemisphere involvement), (2) a greater left ear report in the afternoon (due to greater right hemisphere involvement), (3) a change in laterality as indicated by differences between right ear and left ear report, with a greater REA in the morning for left hemisphere tasks (e.g., verbal tasks) and a greater LEA in the afternoon for right hemisphere tasks (e.g., musical tasks), and (4) a bilateral decline between morning and afternoon testing for tasks purportedly performed by the left hemisphere (e.g., verbal tasks), or, a bilateral increase for tasks purportedly performed by the right hemisphere (e.g., music tasks). However, dichotic performance may also be subject to priming influences (i.e., prior situational factors) which in turn could be affected by time-of-day. Priming in children occurs with such factors as (1) directions to attend left first or right first (Hiscock and Kinsbourne, 1980; Hiscock, Kinsbourne, Caplan and Swanson, 1979; Hiscock and Bergstrom, 1982; Kershner and Morton, 1990) (i.e., an attentional priming effect), and (2) the prior exposure to different stimuli such as music (Morton, Kershner and Siegel, 1990) or CVs and digits (Morton and Siegel, 1991) (i.e., cognitive priming effects). In addition, altering the time of day when testing first occurs influences subsequent performance (Morton and Kershner, in press) (i.e., time-of-daylinked priming effects). To illustrate, Morton and Kershner (in press) noted no differences between reading disabled and control subjects in afternoon testing whereas there were differences in morning testing with the normal-achieving being more proficient. In a second experiment involving normal-achieving children the enhanced performance in the morning was seen to be linked to a priming effect-subjects directed to attend right-ear-first in the morning showed higher overall report for dichotic digits. The opposite pattern was evident in the afternoon. Being directed rightear-first in the morning may preferentially activate the left hemisphere leading to overall better processing. In the afternoon, it seems necessary to activate the right hemisphere (by being directed left-ear-first) in order to obtain the higher results. In view of priming effects and this intriguing link between time-of-day and priming with children (Morton and Kershner, in press) a consideration of order variables would appear to be warranted in dichotic studies, especially when time-of-day effects are a focus. The present study was designed to examine circadian shifts in hemispheric involvement using the dichotic listening technique and tasks linked to the left hemisphere (processing CVs) and the right hemisphere (processing musical melodies). The research design allowed for a consideration of (1) attentional priming (i.e., the effect of being directed to attend left first versus right first), (2) cognitive priming (i.e., the effect of being exposed to the CVs first versus the music first) and (3) time-of-day priming (i.e., the effect of attending in the morning first versus the afternoon first. Incorporating these priming factors in one study allowed for consideration of interesting potential interrelationships. The principal prediction of the study, based on Folkard’s (1979) suggestion of a circadian based shift to more right hemisphere involvement in the afternoon, was
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that subjects would show a laterality shift with relatively more left hemisphere processing in the morning and relatively more right hemisphere processing in the afternoon. Specifically, it was predicted that performance on a left hemisphere task (i.e., phonological processing of CVs) would decline over the course of the day (as measured by a reduced REA, reduced right ear report, or reduced bilateral report) indicative of left hemisphere decline, whereas performance on a right hemisphere task (i.e., processing musical melodies) would improve over the course of the day (as measured by an increased LEA, increased left ear report, or increased bilateral report), indicative of right hemisphere ascendancy. A second more general prediction, based on previous findings with children (Morton and Kershner, in press), was that adult subjects, like children, would show timeof-day linked priming effects, particularly in the morning.
METHOD Subjects
Subjects were university students and recent graduates, in the age range 20-55 years. There were 32 males (27 right-handed, 5 left-handed) and 32 females (26 righthanded, 6 left-handed). The Edinburgh Inventory (Oldfield, 1971) was used to determine subject’s hand preference. Subjects were within the high-average to the aboveaverage range on the WAIS-R vocabulary subtest (scaled score mean = 13.38, SD = 2.79; males, mean = 13.50, SD = 2.79; and females, mean = 13.25, SD = 3.03), and on the WAIS-R block design subtest (scaled score mean = 12.97, SD = 2.23; males, mean = 13.31, SD = 2.16, and females, mean = 12.63, SD = 2.28). Hearing was tested with a Beltone Model 119 Audiometer, set at 25 db, and only subjects with normal hearing, 1000 Hz-8000 Hz range, were selected. Materials and Apparatus
For the dichotic music task, 10 sets of target melodies, 5 seconds in duration, were employed. Two of the melodies were presented, one to each ear, followed, after a four second delay, by four test melodies. These four test melodies were made up of the melody heard in the right ear and the melody heard in the left ear and two extra melodies. Each of these four melodies was separated by a 2 second gap. The CV tape was composed of the six stop consonants paired with a vowel /a/. Each CV was paired once with every other CV for a total of 30 pairs of monosyllables which were presented spaced 7 seconds apart. The tape was produced by Auditec of St. Louis (Rand H-No Delay). The tapes were presented on a Realistic Stereo Dual Cassette Tape Deck SCT-74 connected to a Realistic Digital Synthesized Stereo Receiver STA-2 150. Subjects listened to the tapes with Realistic pro-60 stereo headphones. Digital skin temperature was recorded on a Temp SC201T digital skin temperature monitor. Procedure
For the dichotic tasks an ordered-report, focused-attention paradigm was used. Counterbalancing was implemented for stimulus presented first (CVs first, Music first), for time of first testing (morning first, afternoon first), and for direction attended
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first (directed left first, directed right first). This controlled for practice effects and monitored for various order or priming effects. All subjects were directed to attend to the left earphone. When subjects were directed to attend left, the left earphone would be on the left ear. When subjects were directed to attend right, the left earphone would be on the right ear. This counterbalancing procedure was employed to control for differences in the signal-to-noise ratio between channels. Three warm-up trials were given prior to testing. Continual reminders were given during testing to ensure that subjects were attending as directed. The two listening tasks were heard consecutively, with only a short pause to change tapes and give instructions for the second task. For the CV task, a sheet displaying the CVs (ba, da, ga, ka, pa, and ta) was provided for reference. Subjects were instructed to direct attention to one ear for 30 trials, then switch earphones and direct attention to the other ear for 30 trials. For the dichotic music task the two target melodies were presented followed by four melodies made up of the melody heard in the right ear and the melody heard in the left ear and two extra melodies. The subjects had to identify the target melody by specifying whether it was the first, second, third or fourth melody. These melodies were played in succession with the same set of melodies presented for left ear and right ear trials. Prior to the tasks a Velcro band with an attached temperature probe was affixed to the subject’s left index finger to monitor body temperature during the music tasks. The music task (approximately 20 minutes in duration) provided ample opportunity for the skin temperature to stabilize. The temperature was recorded prior to switching earphones and attending to the other ear. The entire data collection process took a total of 90 minutes per subject. In an attempt to accommodate students’ varied schedules the two test sessions were spaced randomly over a period of several weeks. To ensure that the different test-retest intervals did not influence performance comparisons were made between subjects who had brief test-retest intervals (1-3 days) with those who had longer test-retest intervals (4-21 days) on all dependent variables. There were no differences between the two groups on any of the dependent measures ( p > .OS), and neither did the test-retest interval itself correlate with any of the dependent measures ( p > .05), thus, analyses of variance rather than analyses of covariance were utilized for analysis.
RESULTS Preliminary Analyses Preliminary analyses indicated there were no differences between the two handedness groups. Skin Temperature Digital skin temperature in the afternoon (mean = 32.46 degrees Celsius, SD = 4.46) was significantly higher than the morning (mean = 31.64 degrees Celsius, SD = 4.49), t (63) = 2.95, p < .01, supporting the claim for higher arousal levels in the afternoon (Colquhoun, 1971). Laterulity Indices The results were analyzed using a standard laterality index ((R, - L , / R , + L,) X 100) after Marshall, Caplan, and Holmes (1975). In this index R, = right ear correct report, L, = left ear correct report. Using this index a positive number indicates a REA while a negative number indicates a LEA.
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CV Index A five-way analysis of variance (ANOVA) was computed for the laterality index for CVs with Sex (male, female), Time-Tested-First (morning, afternoon), Ear-Attended-First (left, right), Stimulus-Presented First (CVs, Music) and Time-of-Day (morning, afternoon) as the independent variables. Time-of-Day was the only within-subjects variable and was treated as a repeated measure. There were no main effects, but there was a significant Sex by Time-Tested-First two-way interaction, F(1, 48) = 6.70, p < .025, indicating a time-of-day priming effect (see Figure la). Tests for simple effects (Winer, 1971) indicated males showed higher laterality scores (mean = 22.51) than females (mean = 4.88) when tested moming-first, t(30) = 2.29, p < .05. Females showed higher laterality scores (mean = 15.95) when tested afternoon-first, t(30) = 2.23, p < .05. Means and standard deviations are reported in Table 1. Music Index A similar five-way ANOVA (Sex by Time-Tested-First by Ear-Attended-First by Stimulus-Presented First by Time-of-Day) was computed for the laterality index for music. There were two main effects and one two-way interaction. The main effect for Time-Tested-First, F(1, 48) = 7.53, p < .01, indicated a timeof-day priming effect for both male and female subjects. In effect, there was an overall REA for subjects tested morning-first (mean = 1.44) and a LEA for subjects tested afternoon-first (mean = -4.19). The main effect for Ear-Attended-First, F( 1, 48) = 7.05, p < .025, was due to a REA when directed to attend to the left ear first (mean = 1.35) and a LEA when directed to attend to the right ear first (mean = -4.1). The significant Sex by Stimulus-Presented-First, two-way interaction, F(1, 48) = 6.45, p < .025, indicated a cognitive priming effect (see Figure lb). Tests for simple effects revealed that males showed a LEA (mean = -6.01) when the CVs preceded the music task but a REA when the music task was first (mean = 1.96), t(30) = 2.31, p < .05. Females showed an opposite pattern. Means and standard deviations are reported in Table 2.
Raw Scores The results were subsequently analyzed using the raw scores for the left ear and right ear report for CVs and music in an attempt to explicate the mechanics of the laterality effects. CVs A six-way ANOVA was computed for CVs with Sex (male, female), TimeTested-First (morning, afternoon), Ear-Attended-First (left, right), Stimulus-Presented First (CVs, music) Ear (left, right) and Time-of-Day (morning, afternoon) as the independent variables. Ear and Time-of-Day were within-subjects variables treated as repeated measures. There was a main effect for Ear, F( 1, 48) = 3 1.60, p < .001, which was qualified by a significant Sex by Time-Tested-First by Ear three-way interaction, F( 1, 48) = 8.07, p < .01. Tests for simple effects indicated that males showed depressed left ear scores (mean = 10.1) when tested morning-first compared to females (mean = 13.16), t(30) = 2.14, p < .05, and compared to right ear report (mean = 16.22), t( 15) = 3.49, p < .01. Conversely, females showed enhanced right ear report (mean = 16.81) when tested afternoon-first compared to males (mean = 13.88), t(30) = 2.01, p = .05, and compared to left ear report (mean = 12.19), t(l5) = 4.56, p < .01. Apparently, males show reduced left ear report when primed in the morning which explains the greater laterality score for males tested in the morning first; females show enhanced right ear report when primed in the afternoon which explains
L.L. MORTON rt a / .
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AGURE 1 Laterality index scores for (a) CVs for males and females tested morning-first and afternoon-first showing greater laterality for males tested morning-first and for females tested afternoon-first and (b) music for males and females when CVs are tested first and music is tested first showing the left ear advantage for males when the CVs are presented first and the right ear advantage when the music is first
the greater laterality score for females tested in the afternoon first. Means and standard deviations for the raw scores are reported in Table 3 .
Music A similar six-way ANOVA (Sex by Time-Tested-First by Ear-Attended-First by Stimulus-Presented First by Ear by Time-of-Day) was computed for music stimuli. A main effect along with two-way, three-way and four-way interactions indicated complex effects with respect to musical processing. The main effect for Ear-At-
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TABLE 1 Means and Standard Deviations for the Laterality Index for CVs For Males and Females When Directed To Attend In The Morning First And When Directed to Attend In The Afternoon First Males
Time-Tested-First Morning-First Afternoon-First
Females
Mean
SD
Mean
SD
22.51 10.16
27.11 16.73
4.89 15.95
14.55 13.44
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Note. The laterality index ( ( R , - L,/R, (1975).
+ L,)
X
100) was adopted from Marshall, Caplan and Holmes
tended-First, F(1, 48) = 4.15, p < .05, was qualified by a significant Ear-AttendedFirst by Ear two-way interaction, F( 1, 48) = 12.06, p < .001. This indicates a right hemisphere priming effect which benefits subsequent left hemisphere/right ear performance (see Figure 2a). Tests for simple effects indicated that right ear report for music was depressed (mean = 7.67) (1) when compared to left ear report (mean = 8.16) when subjects were directed to attend to the right ear first, t(3I) = 3.04, p < .01, and (2) when compared to subjects directed to attend to the left ear first (mean TABLE 2 Means and Standard Deviations for the Laterality Index For Music For Males and Females When Tested Using CVs First and When Tested Using Musical Stimuli First Males
Stimuli-Tested-First CVs-First Music-First
Females
Mean
SD
Mean
SD
-6.01 1.96
12.85 5.05
0.50 -1.95
5.67 9.35
Note. The laterality index ((R, - L,/R,
+ L,) X
100) was adopted from Marshall, Caplan and Holmes
( 1975).
TABLE 3 Means and Standard Deviations for the Raw Scores For CVs For Left Ear Report and Right Ear Report For Males and Females When Directed To Attend In The Morning First And When Directed To Attend In The Afternoon First Males
Left Ear Time-Tested-First Morning-First Afternoon-First Right Ear Time-Tested-First Morning-First Afternoon-First
Fenfales
Mean
SD
Mean
SD
10.09 11.59
4.12 4.47
13.16 12.18
3.96 3.01
16.22 13.88
5.74 4.23
14.41 16.81
3.51 4.05
L.L. MORTON er ul.
90
Right Hemisphere Priming Effects
1
Right First
Left First
1
u
; 8.5 e
r
C
8
0
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r
r e
7.5
C
t 7
Left
A
Right
Ear Attended
Time- Of -Day Effect
Morning
R
Afternoon
Time-Of-Day For Doing The Music Task
FII left first and when directed right first showing tne ennancea nght ear report when directed left first (a right hemisphere priming effect) and (b) males and females in morning and afternoon tests showing the low morning performance for males (a time-of-day effect)
= 8.67), t(62) = 2.71, p < .01, Attending to the left ear first acts as a prime (perhaps a right hemisphere prime) that facilitates subsequent attending to the right ear. The Sex by Time-of-Day interaction, F(1,48) = 4.07, p < .05 indicates a timeof-day effect for males (see Figure 2b). Tests for simple effects indicated that males had reduced report in the morning (mean = 7.67) compared to the afternoon (mean = 8 . 2 3 , t(31) = 2.02, p < .05. Females showed high performance in both morning
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TABLE 4 Left Ear Report Means and Standard Deviations For Music For Males and Females In The Morning And Afternoon For Two Order Variables-Stimulus Presented First and Time-Tested First Males Stimulus First CVs-First Time-Tes ted-First Morning-First
M
SD Afternoon-First
M
SD
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Music-First Morning-First
M
SD Afternoon-First
M
SD
Females
Morning
Afternoon
Morning
Afternoon
6.88 1.46 8.00 1.93
7.87 0.99 7.63 1.85
8.38 1.41 8.88 1.25
8.63 1.19 8.50 1.20
7.13 2.17 9.13 0.99
8.63 1.19 8.75 1.28
7.75 1.98 9.00 0.76
8.75 1.39 8.25 1.39
(mean = 8.5) and afternoon (mean = 8.44) testings. Apparently, males are musically disadvantaged in the morning. A practice effect was evident in the Time-of-Day by Time-Tested-First two-way interaction, F( 1, 48) = 16.68, p < .001. Subjects tested first in the morning (mean = 7.7) showed enhanced performance when subsequently tested in the afternoon (mean = 8.61), r(31) = 3.44, p < .01, and subjects tested first in the afternoon (mean = 8.08) showed enhanced performance when subsequently tested in the morning (mean = 8.47), t(31) = 2.16, p < .05. Thus, a practice effect exists for the music stimuli only, and regardless of time tested first. The two two-way interactions (Sex by Stimulus-Presented-First, F( 1, 48) = 6.32, p < .025, and Time-Tested-First by Ear, F(l, 48) = 12.06, p < .01) and the threeway interaction (Sex by Stimulus-Presented-First by Ear, F(1, 48) = 5.05,p < .05) are qualified by the four-way interaction (Sex by Stimulus-Presented-First by TimeTested-First by Ear, F(1, 48) = 3.90, p < .05). Simple effects tests revealed that in the morning-first condition males showed lower music report than females on the left ear (male mean = 7.38; female mean = 8 . 5 ) , t(14) = 2.22, p < .05, and the right ear (male mean 7.5; female mean = 8.75), t(14) = 2.27, p < .05, but only when the CVs were processed first. Figure 3a, which presents difference scores between males and females (i.e., female score minus male score) tested morning-first, portrays this interaction. The CVs are contributing to a priming bias which interferes with the information processing for musical stimuli of males only. There is a difference favoring females but only when the CVs are first. In the afternoon-first condition males showed the same pattern but only for the right ear report. As may be seen in Figure 3b, females have the advantage on music processing when the CVs are presented first, whereas males have the advantage (represented by the negative score) when the music is first. More specifically, males do better than females on the right ear report for music (male mean = 9.06; female mean = 7.68), t(14) = 2.21, p < .05, but only when there is no prior processing of CVs. When the CVs are processed first in the afternoon-first condition the right ear report of the males is still depressed (mean = 6.8), t(14) = 2.5, p < .05. Means and standard deviations are reported in Tables 4 and 5.
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TABLE 5 Right Ear Report Means and Standard Deviations For Music For Males and Females In The Morning And Afternoon For Two Order Variables-Stimulus Presented First and Time-Tested First Males Stimulus First CVs-First Time-Tested-First Morning-First Afternoon-First
M SD M
SD
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Music-First Morning-First Afternoon-First
M SD M
SD
Females
Morning
Afternoon
Morning
Afternoon
6.88 2.90 6.88 2.70
8. I3 0.99 6.75 2.12
8.50 0.93 8.88 1.36
9.00 0.76 8.25 1.17
7.50 2.00 9.00 1.31
9.13 0.84 9.13 0.99
8.63 1.77 8.00 2.00
8.75 1.39 7.38 1.85
DISCUSSION Right Hemisphere Processing In The Afternoon
On the raw scores for music there was a clear time-of-day effect wherein males showed reduced performance in the morning. Given the right hemisphere involvement in music processing (Gates and Bradshaw, 1977: Kimura, 1967) this effect is consistent with a depressed right hemisphere in the morning and provides support for Folkard’s (1979) contention that there may be a shift to more right hemisphere processing in the afternoon. In the present study the effect is clearly evident for males only. Thus, Folkard’s (1979) hypothesis apparently should be further explored in terms of sex and task variables. The predicted circadian shift in laterality was not directly supported by the laterality indices. Evidence for simple laterality shifts was precluded by the various priming effects which were influencing both CV report and music report. Priming Effects Time-of-day-linked priming influences Based on the performance of male children using a dichotic digits task (Morton and Kershner, in press) it had been predicted that adults would show similar time-linked attentional priming effects using different stimuli (i.e., CVs and melodies). The specific priming effect related to time-of-day and direction-attended-first was not directly evident. However, there were compelling, though complex, time-of-day-induced priming effects for CVs and music. A time-of-day induced priming effect was evident on the CV laterality index. Males were more lateralized than females but only when tested morning-first. It was as if the morning test setting primed the left hemisphere for males, manifested by a strong REA. This is consistent with previous findings with children (Morton and Kershner, in press) in which males were seen to perform better in the morning on a dichotic digits task, but only when the left hemisphere (attending right) was primed first. Moreover, that the effect in the present study continued to exist for subsequent afternoon testing over time intervals ranging from 1 to 21 days is consistent with Hiscock and Bergstrom’s (1982) report of a priming effect existing at least one week later.
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When the CV raw scores were analyzed it was apparent that the morning-first priming effect was caused by lower left ear report for males. Conversely, the afternoon-first priming effect for females was caused by increased right ear report. The reason for this sex difference is not clear. It would seem that males are more vulnerable to right hemisphere (left ear) depression as a result of morning-priming. On the other hand females seem to be more amenable to left hemisphere (right ear) engagement as a result of afternoon-priming. Male and female brains may follow different circadian rhythms for arousal or arousal-related hormones which impact upon hemisphere engagement patterns. These sex differences would warrant closer scrutiny in future time-of-day research. The laterality index for music revealed a clear time-of-day-induced priming effect. When subjects were tested morning-first they showed on overall REA on the music stimuli. However, subjects tested afternoon-first showed a LEA. The LEA is the expected effect for musical stimuli (Kimura, 1967). The fact that the LEA exists for subjects tested afternoon-first suggests that the afternoon testing primes the right hemisphere to process the music and this primed right hemisphere is preferentially engaged for subsequent morning testing also. Conversely, exposure to the music task morning-first appears to be a handicapping condition creating a processing bias to the potentially less preferred hemisphere. It would seem that it is not so much the time-of-testing which is important as the time of priming. These time-of-day-induced priming effects may be important for understanding maladaptive learning. It may be the case that time-locked experiences create persistent and longterm biases either facilitating or hindering subsequent learning. This could be a potentially fruitful area for future research. Finally, there was a time-of-day-induced cognitive priming effect for music. It was clear that the prior processing of CVs depressed performance for males on left ear report and right ear report when they were tested first in the morning (see Figure 3a). Furthermore, males were seen to show increased right ear report when there was no prior processing of CVs when the afternoon testing was first (see Figure 3b). Males seem to have a very effective right ear/left hemisphere ability or transcallosal ability, compared to females, for processing musical stimuli at the right ear if they are tested first in the afternoon, and if they are not exposed to CVs first. At the same time, males are seen to be quite vulnerable to situational priming factors such as time-of-day and cognitive precursors. Other priming influences Although these"other" priming effects were not predicted they are interesting and perhaps directive. On the laterality index for music there was a Sex by Stimulus-Presented-First interaction-a cognitive priming effect. The interaction was due to males showing a LEA on the musical stimuli but only when they processed CVs prior to the music. Females do not show this shift. It is as if the CVs prime the males for a LEA on music. Perhaps, the CV task creates a bias to the right ear (left hemisphere) for linguistic stimuli impeding a focus on the right ear for musical stimuli. In fact, an examination of the raw scores for each ear reveals that the prior processing of CVs depresses left ear report and right ear report in males on musical stimuli and that the right ear report is more depressed than the left ear report. This effect is evidence in the three-way interaction (Sex by Stimulus-Presented-First by Ear). Thus, the prior processing of CVs suggests a linguistic bias in males that interferes with subsequent processing of categorically different stimuli. Males may lack attentional flexibility for cognitively different stimuli or stimuli differentially processed by the left and right hemispheres.
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1 D i
Ear
W R i g h t Ear
1.41
f
1.2
f e
l
r e
-Left
1 I
0.8
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0.6
s
0.4
C 0
0.2
r
e
a CVs First
A
Music First
Stimulus-Tested-First
Afternoon-First Priming Effects Left Ear
CVs First
B
R i g h t 4 ______
Music First
Stimulus-Tested-First
FIGURE 3 Difference scores (female minus male score) for melodies reported for left and right ear when CVs were presented first and when music was presented first in (a) the morning-first condition showing females did better than males when the CVS preceded the music task and (b) the afternoonfirst condition showing females did better than males on the right ear report (+ 1.7) when CVs preceded the music task, whereas, males did better than females (- I .4) when the music was first
An attentional priming effect was also evident on the raw scores for music. When subjects were directed to attend to the right ear first they showed depressed right ear report on music stimuli (see Figure 2a). When they were directed to attend to the left ear first their subsequent right ear report increased. High left ear report would be predictable given (1) the preferential access the left ear would have to the right hemisphere and (2) the right hemisphere’s lead in music processing. The fact that there is no difference when subjects are directed left first suggests an attentional
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priming effect or right hemisphere priming effect is operative whereby being directed left first activates the right hemisphere which remains activated to process the musical stimuli (1) directly at the left ear and (2) subsequently, ipsilaterally at the right ear, or across the corpus callosum to the left hemisphere and then to the right ear.
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Conclusions The predicted shift to greater right hemisphere processing in the afternoon was partially supported by male performance on the music task. This is an important finding and indicates the need to consider both the sex variable and different types of stimuli in future time-of-day research. Although complex, the time-of-day-induced priming effects are equally important. These priming effects raise important questions about research design, hemispheric functioning and learning sequences. ln terms of research design, neuropsychological researchers need to be aware of the potential influences of priming effects related to time-of-day , cognitive precursors, and attentional practices. As research studies which examine these variables begin to accumulate, patterns may emerge which would shed light on the rhythms of hemispheric functioning-rhythms that may be informationally driven (e.g., cognitive priming) as well as physiologically drive (e.g ., time-of-day-induced priming). Even information processing sequences may prove to be neuropsychologically important. In terms of learning sequences, one could speculate that the order of curriculum presentation could impact neuropsychologically upon subsequent performance. For example, in school, a music task prior to a reading task, or a spelling task prior to a music task-especially at critical times during the day-possibly could affect hemispheric engagement patterns. The present findings suggest this possibility exists. Obviously, it is premature to suggest educational implications but the possibility of short-term and long-term priming effects warrants continued investigation. Theoretically, these priming effects may be linked to the priming of procedural memory systems (Tulving, 1985; Tulving, Schacter and Stark, 1982) rather than the priming of semantic systems (Chiarello, Burgess, Richards and Pollock, 1990) in view of the extended time lag between priming and priming effect. The priming of procedural memory seems to extend quite readily over long time periods (Hiscock and Bergstrom, 1982; Tulving et al., 1982). Thus, these priming effects may reflect an important infrastructure of learning and learning set related to procedural memory systems. However, at this time, additional research is necessary to explicate fully the nature of these intriguing and potentially important priming effects.
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Folkard, S. (1979). Time of day and level of processing. Memory and Cognirion, 7 , 247-252. Folkard, S. (1982). Circadian rhythms and human memory. In F. Brown and R Graeber (Eds.) Rhythmic aspects of behavior. Hillsdale, New Jersey: Lawrence Erlbaum, pp. 241-272. Gates, A., & Bradshaw, J. L. (1977). The role of the cerebral hemispheres in music. Bruin and Language, 4 , 403-431. Hiscock, M. & Bergstrom, K. J . (1982). The lengthy persistence of priming effects in dichotic listening. Neuropsychologia, 20, 43-53. Hiscock, M. & Kinsbourne, M. (1980). Asymmetries of selective listening and attention switching in children. Developmental Psychology, 16. 70-82. Hiscock, M., Kinsbuurne, M., Caplan, B. & Swanson, J. M. (1979). Auditory attention in hyperactive children: Effects of stimulant medication on dichotic listening performance. Journal of Abnormal Psychology, 88, 27-32. Hiscock, M. & Stewart, C. (1984). The effect of asymmetrically focused attention upon subsequent ear differences in dichotic listening. Neuropsychologia, 25, 507-5 17. Kershner, J. R. & Morton, L. L. (1990). Directed attention dichotic listening in reading disabled children: A test of four models of maladaptive lateralization. Neuropsyrhologia, 28, 181-198. Kimura, D. (1961). Cerebral dominance and the perception of verbal stimuli. Canadian Journal of Psychology, 15, 166-171. Kimura, D. (1967). Functional asymmetry of the brain in dichotic listening. Cortex, 3, 163- 178. Kinsbourne, M. (1975). The mechanism of hemispheric control of the lateral gradient of attention. In M. A. Rabbitt & S. Dornic (Eds.) Attenrion andpegormance V. London: Academic Press. Lavie, P. (1980). The search for cycles in mental performance from Lombard to Kleitman. Chronobiologia. 7 , 247-256. Mackenberg, E. J . , Broverman, D. M . , Vogel, W., & Kleiber, E. L. (1974). Morning-to-afternoon changes in cognitive performances and in the electroencephalogram. Journul of Educational Psychology, 66, 238-246. Morton, L. L. (1986). A single-subject study of the effects of time on task and time of day on productivity and achievement in a dysgraphic student. Canadian Journat for Exceptional Chitdren, 3 , 23-28. Morton, L. L. & Kershner, J . R. (1985). Time-of-day effects upon children's memory and analogical reasoning. The Alberta Journal of Educarional Research. 3 I , 26-34. Morton, L. L. & Kershner, J. R. (in press). Time-of-day effects on neuropsychological behaviors as measured by dichotic listening. International Journal of Neuroscience. Morton, L. L . , Kershner, J . R. & Siegel, L. S. (1990). The potential for therapeutic applications of music on problems related to memory and attention. The Journal of Music Therapy, 27. 195-208. Morton, L. L. & Siegel, L. S. (1991). Left ear dichotic listening performance on consonant-vowel combinations and digits in subtypcs of reading disabled children. Brain and Language, 40, 162180. Tulving, E. (1985). How many memory systems are there'? American Psychologist, 4 0 , 385-398. Tulving, E., Schacter, D. L. & Stark. H. A. (1982). Priming effects in word-fragment completion are independent of recognition memory. Journal of Experimental Psychology: Learning. Memory. and Cognition, 8. 336-342. Winer, B. J. (1971). Sratisrical principles in experimental design. New York: McCraw-Hill.
