Hemispheric emotional asymmetry in a dichotic listening task.

In a dichotic listening experiment white noise was played to one ear and either music or poetry to the other ear. Subjects rated the stimuli on each of three dimensions. The results showed that both music poetry were judged as more pleasant when heard at the left than the right ear. In addition the music, but not the poetry, was perceived as more soothing at the left ear. The findings are discussed in relation to other indications in the literature that left and right cerebral hemispheres differ in their emotional make-up.     

Temporal characteristics of primary-secondary message interference in a dichotic listening task

Previous experiments have shown that during performance of a shadowing task the unattended message is processed at a semantic level. Four experiments are reported that deal with the question of how processing of the unattended message influences the difficulty of shadowing the attended message. Experiment I demonstrated that pupil dilation measures the difficulty associated with a shadowing task. In Experiment II it was shown that during shadowing of 20-item lists pupil dilation decreases as shadowing continues when either words or white noise are in the unattended channel. These results support the idea that it takes time for the attentional mechanism to focus on the attended message. In Experiments III and IV it was found that this decrease in difficulty of shadowing is much less when the attended and unattended messages come from the same stimulus category (letter-letter, digit-digit). The results indicate that, when the unattended message is from the same stimulus category as the attended message, it can interfere with the ability of the attentional system to focus on the attended message.     

Hemispheric performance in detecting prosody: a competitive dichotic listening task

Ross's 1981 model of right-hemisphere processing of affective speech components was investigated within the dichotic paradigm. A spoken sentence constant in semantic content but varying among mad, sad, and glad emotional tones was presented to 45 male and 45 female college students. Duration of stimuli was controlled by adjusting digital sound samples to a uniform length. No effect of sex emerged, but the hypothesized ear advantage was found: more correct identifications were made with the left ear than with the right. A main effect of prosody was also observed, with significantly poorer performance in identifying the sad tone; in addition, sad condition scores for the right ear were more greatly depressed than those for the left ear, resulting in a significant interaction of ear and prosody.     

Reliability of laterality effects in a dichotic listening task with nonverbal material

The present study examined the reliability of a dichotic listening task using nonverbal stimuli. Twenty undergraduate students (all right-handed native English speakers) had to report whether they had heard a target emotion. The task used English words (bower, dower, power, tower) pronounced with an angry, happy, neutral, or sad emotional tone. Results showed a relatively high level of test-retest reliability for the laterality effect. In addition, a significant gender by ear of presentation interaction was obtained. The interaction reflected the fact that a strong left ear advantage was found in females but not in males. The findings indicate that the task used here should be considered a reliable means to assess the lateralization of emotions. Issues concerning the relation between gender and laterality are addressed in the discussion.     

Reliability of laterality effects in a dichotic listening task with words and syllables

Large and reliable laterality effects have been found using a dichotic target detection task in a recent experiment using word stimuli pronounced with an emotional component. The present study tested the hypothesis that the magnitude and reliability of the laterality effects would increase with the removal of the emotional component and variations in word frequency. Thirty-two participants completed both a dichotic syllable detection task and a dichotic word detection task. In both tasks, stimuli were pronounced in a neutral tone of voice. Each task was completed twice to allow the estimation of test-retest reliability. Results failed to confirm the hypothesis since they were generally similar to those obtained in the previous study. A significant right ear advantage (REA) was found only with the word task. Although no ear advantage was found for the syllable task, somewhat better reliability was demonstrated compared to that obtained with words. The present findings suggest that including an emotional component does not reduce the reliability or magnitude of auditory laterality effects. In fact, the emotional component may have forced participants to focus on the language aspects of the stimuli. This might partly account for the reduced reliability in words and the absence of REA in syllables. Motivational factors inherent to the within-subject design used here are also discussed.     

Response competition and target word detection during shadowing in a dichotic listening task

College students (N = 24) served as subjects in a within-subjects study of auditory attention in which four tasks were performed. In the easiest task, a single passage was presented and shadowed while target word detections were indicated by pressing a key. The other three tasks also required target word detection, but a second passage was presented simultaneously. One task had no target words in the unshadowed passage; the other two tasks required a key-pressing response to the target words in both passages, either with one hand or with each hand. We expected performance to decrease as task complexity increased; this was partially confirmed. The task of shadowing and detecting target words is too difficult to be used to test perception or response limitations of attention.     

Hemispheric laterality and dissociative tendencies: differences in emotional processing in a dichotic listening task

The present work investigates whether the hemispheric processing of both verbal and emotional stimuli, studied by means of a dichotic listening task, differs between normal high and low dissociators as assessed by the Dissociative Experiences Scale (DES; Bernstein & Putnam (1986). Development, reliability and validity of a dissociation scale. Journal of Nervous and Mental Disease, 174(2), 727-735). Two groups of subjects (50 high and 50 low dissociators), participated in the experiment. The task consisted in identifying both verbal and emotional stimulus-targets, respectively, on successive sessions. Reaction time and response accuracy were registered and analysed using ANOVA (Analysis of Variance). The interaction between stimuli (verbal, emotional), channel (right ear, left ear), and dissociation level (high, low) reached statistical significance in terms of accuracy measures (d': F(1,98)=4.75; p<.05). Both high and low dissociators exhibited the expected right ear advantage (REA effect) on verbal targets. On the other hand, whereas low dissociators exhibited the expected left ear advantage (LEA effect) on emotional targets, high dissociators failed to follow this typical pattern of hemispheric asymmetry: both hemispheres exhibited similar performances. These results confirm the hypothesis that dissociation is related to changes in hemispheric processing, specifically of emotional information.     

A right-ear advantage for dichotic listening in bilingual children

A dichotic listening task was administered to two groups of right-handed Hispanic children enrolled in bilingual education classes. The younger group's mean age was 9:6, the older group's was 13:6. Two dichotic tapes were used, one in English, one in Spanish, consisting of 60 pairs of words per tape. The words were comparable across languages in terms of frequency, grammatical function, and phonetic composition. The results showed clear and equal right-ear advantages for both groups of subjects and for both languages. As expected, older children scored higher than younger ones, and performance on Spanish was better than on English. Neither of these effects interacted with the ear advantage, however. Ear difference scores did not correlate with proficiency in the second language (as measured by performance on the English tape), but there was a significant correlation (r = .58) between the degree of asymmetry in the two languages. These findings indicate that the left hemisphere is primarily (and equally) involved in processing both languages of bilinguals, and that this pattern appears to remain stable in development.     

Sensation seeking and selective attention: focused and divided attention on a dichotic listening task.

Differences in selective attention as a function of sensation seeking, extraversion, neuroticism, and psychoticism were examined in 108 undergraduates using a dichotic listening task. Dependent measures included shadowing performance, reaction times to a secondary light task, target detection, and recall. The results suggested that high sensation seekers have better focused attention than low sensation seekers, and these effects were strongest on the 1st trials of the shadowing tasks. High sensation seekers did not attend differently than low sensation seekers to words related to their interests (sexual, violent, or drug related). Extraversion was associated with greater recall of these kinds of words, although there were no overall differences in selective attention as a function of Eysenck's dimensions. The role of arousal in personality and attention is discussed, particularly in regard to the response of sensation seekers to task novelty.     

Toward a model of dichotic listening performance

Dichotic listening performance for different classes of speech sounds was examined under conditions of controlled attention. Consideration of the complex of target item and competing item demonstrated that, in general, targets were more accurately identified when the competing item shared no relevant features with it and less accurately identified when the competing item shared place, voice, or manner with the target item. Nasals as well as stops demonstrated a significant right-ear advantage (REA). False alarm rates were very similar for left and right attentional conditions, whereas intrusions from the right ear while attending to the left were far more common than intrusions from the left while attending to the right. Attention is viewed as serving to select the stimuli that will be reported, but at a late stage, and only after the right ear perceptual advantage has had its effect. A model of dichotic listening performance is proposed in which both the ease of localizing the item and the strength of evidence for the presence of the item are relevant factors.     

Time sharing and dichotic listening asymmetry in normal and learning-disabled children

Time-sharing and dichotic listening techniques were used to examine cerebral lateralization for language function in 48 normal and 48 learning-disabled children. All subjects were matched according to age, sex, and handedness. An analysis of results indicated that both nornal and learning-disabled children demonstrated left hemisphere lateralization of language function on the time-sharing and dichotic listening tasks. However, no developmental trends were evident for either group. Differences observed in the performance of the normal and learning-disabled children may relate to how each group utilizes “verbal strategies” and processes simultaneous information in the left hemisphere. The results strongly question the notion that attributes learning disabilities to incomplete or delayed language lateralization and lend support to the notion that cerebral lateralization is not a developmental phenomena.     

Language task effects A comparison of stuttering and nonstuttering children

This study examined the effects of language-elicitation tasks and syntactic complexity on disfluencies of stuttering and nonstuttering children. The total disfluencies occurring on the production of imitated and modeled sentences of varying syntactic complexity was compared for the two groups. Results indicated a significant task effect, but nonsignificant complexity and group effects. Results are discussed within the framework of the “Demands and Capacities” model.     

Development of cerebral dominance: dichotic listening asymmetry in normal and learning-disabled children

The magnitude of the dichotic right-ear advantage was assessed in 48 normal and 48 learning-disabled children representing an age range of approximately 5 years. All subjects were matched according to age, sex, and handedness. An analysis of results indicated a significant right-ear advantage in both the normal and learning-disabled children, but revealed no developmental trends for either group. Differences observed in the performance of the learning-disabled and normal children may reflect variability in selective attention rather than differences in the degree of cerebral lateralization. These results suggest a need for a reconceptualization of the causative factors affecting children with learning disorders and lend support to the notion that cerebral lateralization is not a developmental phenomenon.     

The effect of stimulus type and directed attention on dichotic listening with children

This research investigated the effect of stimulus type and directed attention on dichotic listening performance with children. A sample of 12 (5 male, 7 female; mean age 10.5 years) high academically performing children were administered four types of dichotic stimuli (words, digits, CV syllables, and melodies) in three experimental conditions (free recall, directed left, and directed right) to examine perceptual asymmetry as reflected by the right-ear advantage (REA). While the expected REA for words and CV syllables and the expected LEA for melodies were found under free recall, the directed conditions produced varied results depending on the nature of the stimuli. Directed condition had no effect on recall of CV syllables but had a dramatic effect on recall of digits. Word stimuli and directed condition interacted to produce inconsistent perceptual asymmetry while directed condition reduced overall recall for melodies. The findings lend support to the hypothesis that perceptual asymmetries can be strongly influenced by the type of stimulus material used and the effect of attentional strategy employed.