Recent research has complicated the issue of cerebral asymmetry in time perception. ... 'This paper is based on a thesis submitted by the first author to the University of Dayton ... duration of brief acoustic stimuli more quickly when the stimuli were presented ... (1978) found no evidence of hemispheric specialization in the.
Perceptual amd Motor Skills, 1980, 50, 1239-1246. @ Perceptual and &lotor Skills 1980
CEREBRAL ASYMMETRY I N THE PERCEIVED DURATION OF COLOR STIMULI1 SUE A. KOCH, DONALD J. POLZELLA, AND FRANK DAPOLITO
Uaiversity o/ Dayton Summary.-20 right-handed males pdged rhe duration of small and large colored circles, which were briefly exposed In the left, center, and right visual fields. Perceived duration was a logarithmic function of exposure duration and a positive function of size and chromaticity. Over-all accuracy was equivalent in the left and right visual fields, but the effects of chromaticity and duration on subjects' judgments were asymmetrical. These and other findings suggest a two-process model of time perception in which there is right hemispheric control over a visual information processor and left hemispheric control over a timer.
Experimental evidence suggests that the left hemisphere of the normal human brain processes stimuli linearly and analytically in a verbal mode, while the right hemisphere processes stimuli holistically and synthetically in a spatial mode (Dimond & Beaumont, 1974, pp. 81-84). An essential difference between these two modes of processing appears to be the degree to which a linear conception of time is reflected in thought. In fact, several investigators have demonstrated that the two hemispheres perceive time differently. These demonstrations are premised on the fact that unilateral afferent stimulation leads primarily to stimulation in the contralateral cerebral hemisphere. Efron (1963a, 1963b) asked subjects to judge the simultaneity and temporal sequence of very brief (1 msec.) bilateral stimuli, which were presented in either visual (light flashes) or tactual (electric shocks) modalities. In general, right-handed subjects experienced simultaneity when the left stimulus preceded the right stimulus by approximately 3 or 4 msec. The data were less consistent for left-handed subjects, but, over all, the results indicated that judgments of simultaneity and temporal sequence require the use of the "dominant" hemisphere, i.e., the left hemisphere for most right-handed subjects. There are similar indications in other experiments (Corwin & Boynton, 1968; Oostenbrug, et a/., 1978). Recent research has complicated the issue of cerebral asymmetry in time perception. Erwin and Nebes ( 1976) concluded thac the right hemisphere is primarily responsible for the functional properties of visual persistence. Consistent with this Buchtel, et al. (1978) found that subjects discriminated the 'This paper is based on a thesis submitted by the first author to the University of Dayton in partial fulfillment of the degree of Master of Arts in Psychology. Correspondence should be sent to D. J. Polzella, Department of Psychology, University of Dayton, Dayton, Ohio 45469.
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duration of brief acoustic stimuli more quickly when the stimuli were presented to the left ear than when they were presented to the right ear. However, Bertoloni, et al. (1978) found no evidence of hemispheric specialization in the discrimination of brief visual stimuli. A recent experiment from our laboratory (Polzella, et al., 1977) helps to clarify the issue of cerebral asymmetry in time perception. The results of this experiment indicate that neither hemisphere is "dominant" for time perception. Rather, temporal judgments are the result of integrated bilateral processes. Subjects were asked to judge the duration of random dot patterns, which were briefly flashed to the left and right visual fields. The patterns varied in numerosity (1, 2, 3, 4, or 5 dots) and exposure duration (16, 25, 40, 63, or 200 msec.). The perceived duration of the patterns increased linearly with log duration and monotonically with numerosity. Over-all accuracy was nearly equivalent in both visual fields, but the effects of numerosity on perceived duration were more systematic when the patterns were flashed to the left visual field. The findings were interpreted in terms of Thomas and Weaver's (1975) two-process model of time perception. This model assumes that temporal judgments are obtained from both a visual information processor and a timer. Attention is shared between these processors, and the perceived duration of a filled interval is a weighted average of information processing time and perceived empty duration. In applying the model to the findings, we theorized that the hemispheric distinction serves as an automatic control over the distribution of attention to the two processors, such that, when the stimulus is presented to the right (left) hemisphere, perceived duration is based primarily on the output of the visual information processor (timer). The present experiment was an attempt to extend these findings. The design is similar to that of the previous experiment (Polzella, et al., 1977), except for changes in the stimulus parameters. Subjects were asked to judge the duration of circles, which were briefly flashed to the left, center, and right visual fields. The circles varied in size and color. There are few reports of hemispheric specialization in the perception of size, but size is known to affect perceived duration. In general, large stimuli are judged to last longer than small stimuli (Gomez & Robertson, 1979; Mo & Michalski, 1972; Thomas & Cantor, 1976). There is evidence of hemispheric specialization in color perception, but the evidence is equivocal. Some investigators have reported a right hemispheric superiority ( Davidof f, 1976; Hannay, 1979; Pennal, 1977), others, a left hemispheric superiority (Malone & Hannay, 1978; Schmit & Davis, 1974), still others, no hemispheric superiority (Dirnond & Beaumont, 1972; Dyer, 1973; Hannay, 1979). There are no reports of the effect of color on perceived duration.
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The subjects were 20 right-handed males with normal vision. They participated in order to fulfill a research requirement for an introductory psychology course. Stimali and Apparatas The stimuli were 18 white cards (22.9 cm X 15.2 cm). Each was marked with a small ( 1 0 rnm) or large ( 2 0 mm) orange-red, blue, or grey circle, which was located in the center of the visual field, 2.93" to the left of the center, or 2.93" to the right of the center. The circles were constructed from Color-Aid paper, and chromaticity was measured with a Pritchard photometer under C.I.E. standard Source A illumination. The respective X-, Ycoordinates were ,640, .345 (orange-red); ,297, .274 (blue); and ,463, .416 (grey). The stimuli were exposed singly on an Iconix No. 192 tachistoscopic system.
Procedure Each of the 18 stimuli wzs exposed three times a t each of the three durations: 40 msec., 63 msec., and 100 msec. This yielded 162 stimulus trials, which were ordered randomly for each subject. The subject's task was one of absolute judgment. Following each trial he indicated the duration of the exposure by circling "s" for short (40 msec.), "m" for medium ( 6 3 msec. ), or "1" for long (100 msec.) on a prepared answer sheet. Before viewing the 162 stimuli, the subject received a series of ,practice trials with feedback until he reached a criterion of nine out of 15 correct. In this case, the stimulus was a 15-mm black circle that was randomly exposed to the left, center, and right visual fields. N o feedback was given during the stimulus trials. The subject was merely instructed to stare at a central fixation point on a "ready" command and to record the judged duration of the subsequent flash.
RESULTS The duration judgments were converted to three-point ordinal scale ratings, where "s" = 1, "m" = 2, and "I" = 3. These ratings were summed over the three presentations at each duration. The experimental design was then 3 (visual field) X 3 (duration) X 3 (color) X 2 (size) with repeated measures across all levels of each factor. The data were analyzed with Biomedical Computer Program BMD VOS. Mean judged duration is plotted in Fig. 1 as a function of log duration for each visual field separately. The main effect of visual field was significant (F2,38 = 3.70, p < .05). Temporal judgments were significantly longer in
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FIG. 1. Mean judged duration as a funcrion of exposure duration and visual field presentation
the center visual field; however, the difference between left and right visual field judgments was not significant. There was a strong main effect of duration ( F 2 , 3 8 = 126.69, p < .001), but the interaction of duration and visual field only approached significance ( F 4 . 7 0 = 2.41, p < . l o ) . The main effect of color was significant ( P 2 , 3 8 = 10.96, p < .001). The mean judged durations of orange-red, blue, and grey stimuli were 1.98 ( S D = .19), 1.98 ( S D = .20), and 1.84 (SD = .22), respectively. Thus, the perceived duration of the chromatic stimuli was significantly greater than the perceived duration of the achromatic stimuli. There was also a significant main effect of site ( F 1 , l D = 35.81, p < .001). As expected, large stimuli were judged to last longer than small stimuli. Size significantly interacted with visual field ( F 2 , 3 8 = 3.87, p < .05) and .01). These effects are shown in Figs. 2 and with color ( F p , a 8 = 5.62, p 3, respectively. The figures clearly show that the effects of field and color were magnified with large stimuli. Of the remaining sources of variability, only the four-way interaction was significant ( F 8 , 1 5 2 = 2.88, p < .01). TO interpret this effect separate analyses were computed for each visual field. The main effects of duration, color, and size were significant in each visual field. However, none of the interactions was significant in the center visual field. The three-way interaction of duration X color X size was significant in both the left ( F 4 . 7 6 = 2.65, p < .05), and the right visual fields ( F 4 . 1 6 = 2.88, p < .O5). Both effects are shown in Fig. 4, in which perceived duration is plotted as a function of size and chromaticity' for each exposure duration. The "chromatic" functions represent the average ratings of the orange-red and blue stimuli, and the "achromatic" functions represent the ratings of the grey stimuli. In the left visual field the interaction of color and size is manifested
-10). The proportions of correct judgments in the left, center, and right visual fields were .53, .57, and .53, respectively. However, separate analyses for each visual field indicated cerebral asymmetry. Chromaticity significantly affected accuracy only in the left visual field (Fz,ss = 4.56, p < ,025). This is consistent with the hypothesis of right hemispheric control over the visual information processor. In contrast, while changes in stimulus duration did affect accuracy in the left visual field (FLS8 = 3.80, p < .05), such changes did not affect accuracy in the right visual field (F2,3Y= 2.98, $ > .05). This is consistent with the hypothesis of left hemispheric control over the timer.
DISCUSSION According to the two-process model proposed by Polzella, DaPolito, and Hinsman ( 1977) to account for cerebral asymmetry in time perception, neither hemisphere is more competent in making temporal judgments; however, these judgments do reflect different stimulus parameters. The left hemisphere relies more on temporal information, while the right hemisphere relies more on nontemporal information. The results of the present experiment are consistent with this model. Previous studies indicating cerebral asymmetry in time perception can also be interpreted in this context. For example, Efron's finding (1963% 1963b) of a "simultaneiry center" in the left hemisphere for right-handed subjects reflects the fact that the nontemporal parameters of his stimuli were held constant, and Erwin and Nebes' (1976) findings of greater right hemispheric involvement in visual persistence reflect the fact that the temporal parameters of their stimuli were held constant. In the present experiment in which temporal and nontemporal information was varied, we found evidence of cerebral asymmetry but no evidence of cerebral dominance. Over-all accuracy was equivalent in both visual fields, and the effects of size, color, and exposure duration did not interact (and were thus additive) when stimuli were presented foveally, i.e., when both hemispheres had simultaneous access to stimuli. One problematic finding was that each main effect was significant in both the left and the right visual fields. There would have been stronger support for the two-process model had, say, the main effect of duration been significant only in the right visual field, and color and size significant only in the left visual field. Our failure to observe such clear differences in laterality may have been due to out use of normal subjects. Despite unilateral stimulus presentation, bilateral access to information could not be avoided. This would, of course, attenuate any inherent differences in laterality. Similar experiments using cornmissurotomized subjects would permit a more valid test of the two-process model.
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Increases in size, numerosity, and complexity have been shown to increase the perceived duration of a visual stimulus. Ornstein (1969) proposed that such "illusory" increases reflect a more elaborate encoded representation of the stimulus. Our results suggest that chromaticity has similar effects on perceived duration. In addition, our results support Banks and Barber's ( 1977) recent demonstration that there is chromaticity as well as brightness in information.in iconic memory. REFERENCES BANKS, W. P., & BARBER, G . Color information and iconic memory. Psychological Review, 1977, 84, 536-546. BERTOLONI, G., ANZOLA, G. P., BUCHTEL, H. A., & RIZZOLATTI, G . Hemispheric differences in the discrimination of the velocity and duration of a simple visual stimulus. Neuropsychologia, 1978, 16, 213-220. BUCHTEL.H . A,, RIZZOLATTI,G., ANZOLA. G. P., & BERTOLONI,G. Right hemispheric superiority in discrimination of brief acoustic duration. Neuroprgchologia, 1978, 16, 643-647. CORWIN,T. R., & BOYNTON, R. M. Transitivity of visual judgments of simultaneity. Journal o f Experimental Psj~chology,1968, 78, 560-568. DAVIDOFP,J. Hemispheric sensitivity differences in the perception of color. Quarterly Journnl o f Experimenaal Psychology, 1976, 28, 387-394. DMOND, S., & BEAUMONT, G. Hemisphere function and color naming. Journal o f Experimen~al Psychology, 1972, 96, 87-91. D:MOND, S. J., & BEAUMONT,J. G. Experimental studies of hemisphere function in the human brain. In S. J. Dimond & J. G. Beaumont (Eds.), Hemisphere function in the human brain. New York: Halstead Press, 1974. Pp. 48-88. DYER,F. N. Interference and facilitation for color naming with separate bilateral presentations of the word and color. Journal o f Experimental Prychology, 1973, 99, 314-317. EFRON, R. The effect of handedness o n the perception of simultaneity and temporal order. Brain, 1963, 86, 261-284. ( a ) EFRON, R. The effect of stimulus intensity on rhc perception of simultaneity in rightand left-handed subjects. Brain, 1963, 86, 285-294. (b) ERWIN, D. E., & NEBES, R. D . Right h e m ~ s p h e r ~ cinvolvement in the functional properties of visual persistence. Paper presented at the meeting of the Eastern Psychological Association, New York, April, 1976. GOMEZ, L. M., 8: ROBERTSON, L. C T h e filled duration illusion: the function of temporal and nontemporal set. Perception and Psychophysics, 1979, 25, 432-438. HANNAY.H . J. Asymmetry in reception and retention of colors. Brain and Language, 1979, 8, 191-201. MALONE,D . R., & HANNAY.H . J. Hemispheric dominance and normal color memory. Nerrropsychologia, 1978, 16, 51-59. Mo, S. S., & MICHALSKI,V. A. Judgment of temporal duration of area a s a function of stimulus configuration. Psychonomic Science, 1972, 27, 97-98. OOSTENBRUG,M. W. M., HORST, J. W., & KUIPER,J. W. Discrimination of visually perceived intervals of time. Perception and Psychophysics, 1978, 24, 2 1-34. ORNSTEIN,R. E. O n the experience o f time. Middlesex, England: Penguin, 1969. PENNAL,B. E. Human cerebral asymmetry in color discrimination. Neuropsychologia, 1977, 15, 563-568. POLZELLA,D . J., DAPOLITO, F., & HINSMAN,M. C. Cerebral asymmetry in time perception. Perception and Psychophysics, 1977, 2 1, 187-192.
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SCHMIT,V., & DAVIS, R. The role of hemispheric specialization in the analysis of Stroop stimuli. Acta Psychologica, 1974, 38, 149-158. THOMAS,E. A. C., & CANTOR,N. E. Simultaneous time and size perception. Perception and Psychophysics, 1976, 19, 353-360. THOMAS,E. A. C., & WEAVER,W. B. Cognitive processing and time perception. Perception and Psychophysics, 1975, 17, 363-367.
Accepted April 24, 1980.
