Laterality effects in the processing of syllable structure.

Recent phonological research has shown that the syllable plays a major role in the phonology of German. The present study investigates laterality effects in the processing of syllable structure by means of dichotic presentation of German word pairs that differ in number of syllables, but that differ minimally in the phonemes they comprise (e.g., BREIT and BEREIT). Results showed a sex difference in laterality for the processing of the experimental stimuli, with a greater right-hemispheric lateralization in men and a more bilateral organization in women.     

Laterality effects in processing tonal and atonal melodies with affective and nonaffective task instructions

Right-handed university subjects were presented with monaural melodies that either conformed to the rules of the Western tonal system (tonal melodies) or that systematically deviated from it (atonal melodies) while containing similar contours and pitch skips. Subjects were tested under two different task instructions. One group was requested to judge whether each melody sounded correct or not (the nonaffective task); the other group had to judge whether each melody sounded pleasant or not (the affective task). The nonaffective task was found to elicit essentially no ear difference. In contrast, the affective instruction induced opposite and reliable laterality effects, depending on the valence of the response. The pleasant responses were indicative of a left hemisphere predominance and the unpleasant responses of a right hemisphere predominance. The results are consistent with the claim that the left hemisphere is biased toward positive emotions and the right to negative emotions. Moreover, the results suggest that affective appreciation of melodies is dissociable from their nonaffective judgment.     

Laterality of phonological working memory: dependence on type of stimulus,memory load,and sex

Investigations of the laterality of phonological working memory have not always yielded consistent results. The present experiment investigated working memory for letters and numbers in two memory load conditions. In the low load condition, working memory for letters and numbers was similar. However, in the high load condition, males were more accurate at the recall of letters. This effect was not observed with numbers, in which both sexes performed more poorly. Furthermore, we observed consistent RVF advantages for both tasks, although males were more asymmetrical for the recall of letters and females were more asymmetrical for the recall of numbers. This result indicates that laterality of working memory for letters and numbers differs, and these asymmetries depend upon the sex of the participant.     

Laterality and modality-specific effects of chronic pain

Previous investigations indicated that thresholds to nonpainful tactile stimuli were elevated in chronic-pain patients when compared with pain-free individuals (Seltzer & Seltzer, 1986; Seltzer et al., 1988). The present study attempted to determine whether thresholds to tactual and visual stimuli also were elevated by chronic pain. Furthermore, lateralization of the pain effect on tactile thresholds was assessed by obtaining thresholds from both left and right arms. A decrease in tactile sensitivity to nonpainful stimuli in chronic-pain patients was confirmed, but laterality of the effect was not demonstrated. Visual thresholds were not significantly affected by chronic pain. The data in the present study, taken together with other data, support the proposition that pain does not affect right hemispheric processes more than left hemispheric processes.     

Laterality effects in perceptual matching

Two experiments are reported in which Ss had to indicate whether pairs of simple geometric forms were “same” or “different.” In Experiment I the two forms were either both in the left visual hemifield or both in the right hemifield. Reaction times were unaffected by the locus of the stimuli. In Experiment 2, in addition to left and right pairs, there were pairs in which one of the stimuli was on the left and the other was on the right. Under these conditions, reaction times were faster for pairs totally on the left than for pairs totally on the right. The data support the notion that implicit scanning patterns are important in determining laterality differences. When such scanning is not involved and when simple nonverbal stimuli and responses are employed, laterality differences are eliminated.     

Laterality effects in visual information processing: Hemispheric specialisation or the orienting of attention?

The notion that visual laterality patterns may be attributable to attentional allocation rather than hemispheric specialisation was examined in three experiments. In Experiment I, high verbal ability subjects were found to be less lateralised on a letter name match task than low verbals. In Experiment II, stimulus probability was shown to affect laterality patterns for name but not for physical matches. Again, low verbals were affected more than highs. Experiment III produced results identical to those of Experiment II although, in the latter experiment, visual fields were defined vertically rather than horizontally from the midline. Together, these results support the following generalisations: (1) visual asymmetries have their locus in a post-perceptual information processing stage; (2) visual asymmetries may be altered by manipulating stimulus probability; (3) verbal ability differences in laterality may not reflect neuroanatomical differences but merely cognitive capacity and (4) it may be unnecessary to invoke differential hemispheric specialisation in order to account for visual lateral asymmetries.     

Laterality effects with visual perception of

Using the paradigm denoting a contralateral relationship between visual field and brain hemisphere, laterality effects with music notation and dots were investigated. Two groups of readers of advanced piano music were selected, one good, one poor. Each group participated in two visual half-field experiments, one using random dot patterns and the other using musical chords. Significant opposite field effects were found for the two kinds of stimuli across reading groups, the left field for dots and the right field for chords. With dots, a significant sex effect emerged, with males superior to females across groups. The only significant group difference appeared in the chord experiment, in which the good group was superior. A practice effect also was found only with chords. Results suggest that the left hemisphere is more important for recognition of music notation than the right.     

Differential effects of stimulus context in sensory processing

Stimulus contexts in which different intensity levels are presented to two sensory–perceptual channels can produce differential effects on perception: Perceived magnitudes are depressed in whichever channel received the stronger stimuli. Context differentially can affect loudness at different sound frequencies or perceived length of lines in different spatial orientations. Reported in hearing, vision, haptic touch, taste, and olfaction, differential context effects (DCEs) are a general property of perceptual processing. Characterizing their functional properties and determining their underlying mechanisms are essential both to fully understanding sensory and perceptual processes and to properly interpreting sensory measurements obtained in applied as well as basic research settings.     

Laterality and modality-specific effects of chronic pain.

Previous investigations indicated that thresholds to nonpainful tactile stimuli were elevated in chronic-pain patients when compared with pain-free individuals (Seltzer & Seltzer, 1986; Seltzer et al., 1988). The present study attempted to determine whether thresholds to tactual and visual stimuli also were elevated by chronic pain. Furthermore, lateralization of the pain effect on tactile thresholds was assessed by obtaining thresholds from both left and right arms. A decrease in tactile sensitivity to nonpainful stimuli in chronic-pain patients was confirmed, but laterality of the effect was not demonstrated. Visual thresholds were not significantly affected by chronic pain. The data in the present study, taken together with other data, support the proposition that pain does not affect right hemispheric processes more than left hemispheric processes.     

Cardiac activity and information processing: the effects of stimulus significance, and detection and response requirements.

In two experiments, measures of heart rate and electromyographic activity were obtained from 40 male undergraduates while they performed two series of trials involving a sequential information processing task. Each trial consisted of a warning light, three successive tones, and a responded light, separated by 6-sec intervals. In Experiment 1, subjects responded only if the three tones were of different frequencies. Acclerative heart-rate responses to the last tone increased as a function of the significance of that tone. Subsequent cardiac decelerations were only observed if the subject was preparing to make a response. These results were replicated in Experiment 2, in which subjects responded only if two of the preceding tones were of the same frequency. Electromyographic activity was not significantly affected by stimulus significance or response anticipation. The data indicate that cardiac acceleration and deceleration reflect two independent psychological processes, associated with information-processing and decision-making activity on the one hand, and preparatory activity on the other.     

Laterality effects in the method of triads

The method of triads for psychophysical judgments was analyzed in terms of the unidimensional unfolding model of Coombs (1964). This model predicts laterality effects on the stochastic transitivity of triples for which existing models have been unable to account. An experiment was conducted in which triadic judgments were made on circles differing in area. The results confirmed the stochastic transitivity predictions, but a quantitative formulation of the model proved unsatisfactory.     

Redundancy gains and costs in cognitive processing: effects of short stimulus onset asynchronies

In 7 experiments, the influence of varying stimulus onset asynchronies (SOAs) on the processing of redundant information about words and pseudowords was investigated. All stimuli were visually presented once or twice with 2 copies of the same item flashed either simultaneously or with short SOAs between presentations. The experiments revealed a redundancy gain for words that was absent for pseudowords. Furthermore, the redundancy gain disappeared at an SOA of 50 ms, and there was a gradual performance decline at longer SOAs. However, probing SOAs of 150 and 300 ms revealed that, compared with presentation of 1 target stimulus alone, words were processed significantly faster when target and redundantcopy appeared with a 150-ms lag. The results are tentatively explained in a neurocognitive framework.     

Intelligence and the processing of stimulus structure

It has been demonstrated in a number of experiments that the difficulty level of several performance type intelligence test tasks is determined directly by stimulus and task variables that vary the information to be processed. The variables are quantifiable. The implications of these findings for intelligence and the problems of an experimental approach to the measurement of intelligence are discussed.     

Memory scanning,introversion-extraversion,and levels of processing

Individual differences in information processing were studied in the form of the hypothesis that arousal, as indexed by a personality measure of introversion-extraversion, affects the speed with which certain kinds of processing are completed. The Sternberg paradigm was used, and the results suggested that introverts and extraverts scanned for physical features equally rapidly, but that introverts were slower than extraverts at scanning for the semantic features of category membership. There was limited support for the hypothesis that introverts, thought to be more aroused than extraverts, are less able to engage in shared or parallel processing. It was concluded that information processing in introverts and extraverts may differ qualitatively as well as quantitatively.     

Queer sentences,ambiguity, and levels of processing

Subjects judged linguistic strings "meaningful" or "meaningless." Meaningful sentences were identical for all subjects; however, for each of five groups, meaningless foils containing different kinds of linguistic violation were interspersed among the meaningful sentences. Type of foil influenced processing time for meaningful items, suggesting that laboratory language processing may be determined by the entire set of linguistic materials used. Effect of foil type on comprehension depth for meaningful items was assessed from the extent to which three kinds of ambiguity slowed judgments on those items as compared to unambiguous sentences. Foil type appears to affect depth of meaningful sentence processing in such a way as to support a "levels of analysis" view of sentence comprehension. Foil type and kind of ambiguity interacted to suggest that sentence comprehension requires computation of underlying logical relationships prior to computation of surface structural relationships and the unequivocal determination of word meanings.     

List structure,monotony, and levels of processing

Three experiments were designed to study the effect of the monotony of experimental lists on the level of processing of auditorily presented words. Monotonous lists were homogeneously made up of monosyllabic items and were contrasted to heterogeneous lists containing monosyllabic and bisyllabic items. The subjects' task consisted, first, in carefully listening to an experimental list made up of an equal number of words and nonwords, and second, in subjectively evaluating the actual number of words having been presented to them. Globally, it was found that subjects underestimate the number of words contained in homogeneous monosyllabic lists but not in heterogeneous ones. The first two experiments revealed that such a result held whatever the frequency of the words presented. The third experiment showed that the use of concrete words did not affect the subjective estimation of the number of words in homogeneous lists. It was concluded that words are differentially encoded as a function of the structure of the experimental list in which they are embedded. Taken together, these results suggest that the performance differences observed as a function of the list type originate in the encoding rather than retrieval processes.