Patterns of cerebral lateralization of unfamiliar music were examined in a group ... complex array of task and subject variables (Bever, 1980; Gates & Bradshaw,.
Psychomusicology, 11, 119-124 ©1992 Psychomusicology
CEREBRAL LATERALIZATION OF UNFAMILIAR MUSIC PERCEPTION IN NONMUSICIANS Richard C. LaBarba Sheryl A. Kingsberg Patricia K. Martin University of South Florida Patterns of cerebral lateralization of unfamiliar music were examined in a group of nonmusicians. A dual-task design procedure that controls for attentional tradeoff effects in a concurrent motor and music processing task was used to determine laterality effects. A pattern of asymmetric interference for melody perception of unfamiliar music was observed among 20 right-handed, musically naive subjects. Significant right-hand tapping suppression during a concurrent melody processing task revealed asymmetrical interference between concurrent tasks in the absence of any attentional tradeoff effects. These results suggest that the cognitive processing involved in complex, unfamiliar melody perception among dextrals is largely lateralized to the left hemisphere. They further demonstrate the feasibility of the dual-task paradigm for studying music lateralization. Contrary to earlier views, the cerebral lateralization of music function is no longer considered a differential specialization of the right hemisphere alone. Just as the various components of language are not equally lateralized to the left hemisphere, the data on cerebral processing and control of music perception and production indicate that the localization of music function depends on a complex array of task and subject variables (Bever, 1980; Gates & Bradshaw, 1977a, 1977b; Gordon, 1983; Marin, 1982; Peretz, Morais, & Bertelson, 1987). Studies of music lateralization in normal subjects reveal different laterality patterns depending upon (a) cognitive processing requirements (melody, harmony, timbre, rhythm, and dynamics); (b) subject characteristics such as handedness, musician/nonmusician, music interests, and emotionality/imagery factors; and (c) experimental methodology (dichotic listening tasks, physiological measures, and dual-task paradigms). Among the studies of behavioral asymmetries in music perception, the majority of experiments reported in the literature have used the dichotic listening technique (Kimura, 1964). Very few investigators have employed asymmetries of interference between concurrent tasks to infer lateralization of music perception or production (Beaumont, 1981; Hicks, 1975; Ibbotson & Morton, 1981;Kinsbourne&Hicks, 1978; LaBarba& Kingsberg, 1990; LaBarba, Kingsberg, Martin, & Pellegrin, 1989; Smith, Chu, & Edmonston, 1977). Researchers who use these techniques to determine laterality effects in the perception of various music elements report evidence for various patterns of interference on concurrent tasks. The results from most of these studies, like those from the dichotic listening studies, are equivocal, inconsistent, or difficult to interpret. Inferences of lateralization based on dichotic presentations of music stimuli, often pure tones and difficult monaural perceptual tasks, are LaBarba, Kingsberg, and Martin
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ecologically questionable, yielding auditory asymmetries that may be artifacts of the technique rather than indices of hemispheric asymmetries (Bever, 1980; Gordon, 1983). The majority of the concurrent task studies cited above fail to control for asymmetrical tradeoffeffects (attentional shifts) between tasks (Kinsbourne & Hiscock, 1983). In these instances, the reported results cannot be clearly interpreted as interference asymmetries. The dual-task paradigm (Kinsbourne & Hicks, 1978; Kinsbourne & Hiscock, 1983) is now widely used in behavioral investigations of language lateralization. However, its use in studies of lateralization phenomena in other cognitive functions has been limited, largely because of the difficulties in quantifying and measuring performance on the concurrent tasks, particularly the nonmotor tasks. This control is essential in dual-task designs in as much as it provides the means to compare baseline performance levels with those observed during dualtask procedures. If asymmetrical shifts of attention occur on the concurrent task relative to baseline performance (tradeoff effect), any observed indices of lateralization effects are confounded. In the present dual-task study, cerebral lateralization patterns for the perception of orchestral presentations of unfamiliar music were examined among a group of dextral nonmusicians. It was hypothesized that subjects would display selective interference in right-hand tapping while simultaneously processing unfamiliar music passages, suggesting left cerebral lateralization for unfamiliar melody perception (Bever & Chiarello, 1974; Gates & Bradshaw, 1977a, 1977b). By controlling for familial sinistrality, we also wished to partially replicate and extend previous findings of similar lateralization patterns (LaBarba & Kingsberg, 1990). Method Subjects Twenty undergraduate university students (10 males and 10 females) with no formal music background or training volunteered to participate in the experiment. Subjects ranged in age from 19 to 26, with an average age of 22. All subjects were screened for normal hearing. Only right-handed subjects, as assessed by the Edinburgh Handedness Inventory (Oldfield, 1971), with no history of familial sinistrality were included in the study. Procedure An Apple II Plus computer was used for finger tapping. The keyboard was placed in front of each subject such that the M, N, and J keys could comfortably be reached with the right and left index fingers. For right-hand tapping, subjects were required to alternately tap the M and J keys with the index finger, beginning with the M key. The N and J keys were used for left-hand tapping, beginning with the N key. The number of taps produced during the experimental trials were recorded directly on the monitor screen, which the subjects could not see. During tapping sessions, subjects were instructed to hold their wrist flatly on the table top, with the thumb and palm of the hand resting on the base of the keyboard. This positioning served to stabilize the tapping hand and to 120
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minimize movements other than that of the index finger. Each subject was given 30-second practice trials with right- and left-hand tapping to familiarize them with the proper tapping technique and positioning. The equipment used for the music perception tasks consisted of a Realistic stereo cassette tape deck (SCT-24) amplified by a Realistic AM/FM receiver (Model 12-1401). Music selections were presented stereophonically through a pair of Realistic PRO 20 headphones connected to the receiver output jack. The output volume was preset at 55 dB SPL through a 1000 Hz filter octave band. The sound pressure level at peak was approximately 55 dB, with a range of 5259 dB. The experimenter also wore headphones to monitor music presentations to each subject. Subjects received tape-recorded instructions describing the experiment as one designed to see how well they could perform two tasks simultaneously; tapping as rapidly as possible with the right or left hand, and listening to a passage of classical music for later melody recognition. Each subject received two practice listening trials in which a music passage was heard for 15 seconds. Subjects were told to concentrate as best as possible on the melody only and not the instrument or instruments in the music selection. The 15-second selection was followed by a 5-second silent period that signaled the presentation of four music selections, each separated by a 5second silent period. Subjects were instructed to report whether each of the four choices was the melody they heard first by saying "yes" or "no" during the 5-second silent interval separating the four choices. All subjects readily learned the correct procedure for responding to the melody recognition task during the training trials. Subjects then received an additional two practice trials in the dual-task situation. They listened to two music selections for melody recognition while tapping with the right hand and then the left hand. It was determined that subjects clearly understood the tasks and procedures before proceeding to the experimental trials. No subject required additional training sessions. Baseline Measures. Subjects were given 15-second trials of tapping alone with each hand to obtain baseline measure of right- and left-hand tapping rates. Instructions to tap as rapidly as possible with each hand when given a "Go" signal were repeated. Subjects sat before the computer keyboard and were asked to fixate their eyes on a white square of paper taped to the wall three feet away. The starting hand for baseline tapping was counterbalanced so that half the subjects started with the left, and half with the right hand. Baseline measures for melody recognition alone were then obtained. Subjects were presented two 15-second passages of music, each followed by the four choices, one of which was the identical 15-second passage originally heard. The other three incorrect music presentations were passages from the same piece of music, in which the same solo instrument was heard, but from another movement of the music selection. The total possible number of correct responses in the baseline melody recognition measures was eight. For baseline melody recognition, subjects heard the opening 15-second passage from the first movement of the Concerto in G Major for Flute, Strings, and Continuo by Albinoni. The LaBarba, Kingsberg, and Martin
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second baseline measure was the first 15 s of the first movement of the Concerto for Oboe and String Orchestra by Cimarosa. These selections, like all the music selections used in this experiment, were chosen for their relative unfamiliarity to subjects with no music training or background. Dual-Task Measures. There were four dual-task trials, two 15-second concurrent tapping/music trials for each hand, with the starting hand counterbalanced across subjects. The following music selections were used in the dualtask trials: by Stamitz Concerto No. 3 in Bb Major for Clarinet and Orchestra (first 15 s of the third movement), by Corelli Concerto in F majorfor Oboe and Strings (first 15 s of the Gigue movement), by Haydn, CWfo Concerto in D Major (first 15 s of the first movement), and the Piano Concerto in C Major, K. 415, by Mozart (first 15 s of the third movement). Each of these target melodies was tested for melody recognition by requiring subjects to identify the melody from three 15-second passages from other movements of the concertos. The total possible number of correct responses in the melody recognition portion of the dual-task was eight, as in the baseline measure. Subjects were instructed again to tap as rapidly as possible, when given the signal to begin, while simultaneously listening to the target melody. In this manner, it was possible to obtain comparison measures of both motor and nonmotor tasks for analysis of tradeoff effects. At the end of the experimental trials, subjects were asked if any of the melodies they heard were familiar to them. Only two subjects reported familiarity with two melodies, but could not identify them by name or composer. Results The data were analyzed in a mixed model ANOVA with one between (gender) and two within (hand and condition) variables. The mean tapping rates in the baseline and dual-task conditions for males and females, and means collapsed across gender, are shown in Table 1. A significant hand effect was found [F (1, 18) = 6.20, p < .02]. A subsequent post hoc LSD test (Tukey, 1953) revealed that right-hand tapping (75.5) during the baseline condition was significantly higher (p < .01) than the number of taps produced in the dual-task condition (70.9). The mean tapping rates for Table 1 Mean Number of Taps in 15-second Trials for Baseline and Dual-task Conditions Male Female Male & Female LH RH RH LH LH RH 74.7 65.1 Baseline 76.3 66.3 75.5 65.7 12.7 SD 8.8 10.3 8.7 11.3 8.5
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Dual Task
70.6
64.3
71.3
64.4
70.9
64.4
SD
10.7
9.6
7.1
6.2
8.8
7.8
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the left hand in the baseline and dual-task conditions were not significantly different (65.7 and 64.4, respectively). No gender differences were observed in the laterality patterns of tapping suppression in the dual-task condition. A subsequent ANOVA to determine tradeoff effects between baseline and dual-task melody recognition conditions indicated that no attentional tradeoff effects occurred in the dual-task situation. There were no significant differences between the mean number of correct melody recognitions in the baseline (6.2) and dual-task conditions with concurrent right-hand (6.6) and left-hand (6.5) tapping. There were no gender differences in melody recognition accuracy. Right-hand tapping suppression in the dual-task condition was found among 16 of the 20 subjects, with the remaining subjects showing no change. Nine males and seven females showed a reduction in right-hand tapping during the concurrent melody task. Discussion The results of this experiment support our hypothesis of selective interference for perception of orchestral presentations of unfamiliar music in the dualtask paradigm. The laterality patterns in finger tapping reveal significant decrements in right-hand tapping during concurrent music processing for both males and females. These findings suggest that cognitive processing of unfamiliar music as presented in this study is largely lateralized to the left hemisphere among dextral nonmusicians. We found no evidence of tradeoff effects in accuracy of melody recognition musically from baseline to dual-task conditions, strengthening the conclusion that the observed asymmetry in right-hand tapping reflects true cerebral interference effects and not simply an attentional shift between dual-tasks. These results are consistent with those reported by Gates and Bradshaw (1977a, 1977b) in a dichotic listening paradigm. These data provide additional evidence that the cerebral processing strategies involved in unfamiliar melody perception include left cerebral hemisphere activation. The implication is that this cognitive task requires increased analytical processing relative to that reportedly involved in the perception of familiar melodies (Gates & Bradshaw, 1977a, 1977b). We have reported similar, but more complex, patterns of lateralization of music perception in an earlier study (LaBarba & Kingsberg, 1990). In that study, however, bilateral activation of the cerebral hemispheres was observed in response to both familiar and unfamiliar music perception, with left cerebral activation significantly greater than that of the right hemisphere. This patterning of lateralization suggests that although orchestral presentations of complex melodic contours recruit bilateral cerebral activity, overall, integrated cognitive control of such processing strategies may be under the direction of the left cerebral hemisphere. In the present study, the data suggest a pattern of cerebral organization for music perception which differs from that often reported in the contemporary literature, and certainly from that of classical neuropsychology. The dual-task paradigm as applied in our studies of music lateralization has yielded fairly LaBarba, Kingsberg, and Martin
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consistent results, and has been shown to be a fruitful behavioral approach to the investigation of lateralization phenomena. References Beaumont, J.G.(1981). Activation and interference in tactile perception. Neuropsychologia, 19, 151-154. Bever, T.G. (1980). Broca and Lashley were right: Cerebral dominance is an accident of growth. In D. Caplan (Ed.), Biological studies of mental processes (pp. 97115). Cambridge, MA: MIT Press. Bever, T.G., &Chiarello, R.J. (1974). Cerebral dominance in musicians andnonmusicians. Science, 185, 137-149. Gates, A., & Bradshaw, J.L. (1977a). Music perception and cerebral asymmetries. Cortex, 13, 390-401. Gates, A., & Bradshaw, J.L. (1977b). The role of the cerebral hemispheres in music. Brain and Language, 4, 403-431. Gordon, H.W. (1983). Music and the right hemisphere. In A.W.Young (Ed.), Functions of the right hemisphere (pp. 130-146). New York: Academic Press. Hicks, R.E. (1975). Intrahemisphere response competition between vocal and unimanual performance in normal adult human males. Journal of Comparative Physiology and Psychology, 89, 50-60. Ibbotson,N.R.,& Morton, J. (1981). Rhythm and dominance. Cognition, 9, 125-138. Kimura, D. (1964). Left-right differences in the perception of melodies. Quarterly Journal of Experimental Psychology, 16,355-358. Kinsbourne, M„ & Hicks, R.E. (1978). Mapping cerebral functional space: Competition and collaboration in human performance. In M. Kinsbourne (Ed.), The asymmetrical function of the brain (pp. 267-273). New York: Academic Press. Kinsbourne, M., & Hiscock, M. (1983). The normal and deviant development of functional lateralization of the human brain. In M.M. Haith & J.J. Campos (Eds.), Handbook of child psychology, Vol. 2 (pp. 157-280). New York: Wiley. LaBarba, R.C., & Kingsberg, S. A. (1990). Cerebral lateralization of familiar and unfamiliar music perception in nonmusicians: A dual task approach. Cortex, 26, 567574. LaBarba, R.C., Kingsberg, S.A., Martin, P.A., & Pellegrin, K. (1989). Cerebral lateralization of music perception in the dual task paradigm: Unfamiliar melody recognition in sinistrals. Neuropsychologia, 27, 247-250. Marin, O.S.M. (1982). Neurological aspects of music perception and performance. In D. Deutsch (Ed.), The psychology of music (pp. 83-98). New York: Academic Press. Oldfield, R.C. (1971). The assessment and analysis of handedness: The Edinburgh Inventory. Neuropsychologia, 9,77-113. Peretz, I., Morais, J., & Bertelson, P. (1987). Shifting ear differences in melody recognition through strategy inducement. Brain and Cognition, 6, 202-215. Smith, M.O., Chu, J., & Edmonston, WE. (1977). Cerebral lateralization of haptic perception: Interaction of responses to Braille and music reveals a functional basis. Science, 197, 689-690. Tukey* J.W. (1953). The problem of multiple comparisons. Unpublished manuscript, Princeton University, Princeton, NJ. Author Notes Requests for reprints should be sent to Dr. Richard C. LaBarba, Department of Psychology, University of South Florida, Tampa, FL 33620.
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