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.     

Ear asymmetry in a dichotic detection task

Pairs of consonant-vowel (CV) syllables were presented dichotically to Ss who were instructed to monitor for the presence of a target CV which could occur in either ear. Ss responded by depressing a response button ; reaction time (RT) was also recorded. Right ear targets were detected 6.2% more frequently, on the average, than left ear targets and had an average RT 50 msec quicker than their left ear counterparts. These results demonstrate the existence of a right ear superiority in dichotic listening when a nonverbal motor response measure is used, supporting the contention that the ear asymmetry phenomenon is truly perceptual in nature and not merely due to the lateralization of verbal output. Two alternative explanations of the RT difference between left and right ear targets are offered. One attributes this difference to the time necessary for intercortical transfer of right hemisphere information, while the second holds that it is due to the longer times needed by the right hemisphere to process information projected to it.     

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.     

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.     

Dependent processing in dichotic listening as a function of word meaning attributes

Single dichotic word pairs were presented for immediate identification. Recognition probability was greater and response latencies shorter for high- than for low-frequency words. Both recognition measures were also affected by the frequency of the word accompanying the target word, performance being facilitated by a high-frequency partner and sometimes impaired by a low-frequency partner. Associative meaningfulness had similar, though less reliable, effects whereas the effects of word concreteness-abstractness were inconsistent. Recognition accuracy was generally superior for right-ear inputs, but recognition latency did not show consistent ear effects. Similar results were obtained under both unrestricted (Experiment 1) and controlled (Experiment 2) ear order of report instructions. The findings are consistent with a limited capacity interpretation of secondary processing in word perception.     

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.     

Simultaneous masking in a dichotic emotion detection task

The present study investigated the possible role of ceiling effects in producing laterality effects of small magnitude in dichotic emotion detection. Twenty two right-handed undergraduate students participated in the present experiment. They were required to detect the presence of a target emotion in the expressions tones of happiness, sadness, anger, and neutrality presented dichotically. Stimuli were adjusted to 70 dB and occurred simultaneously with a white noise mask that had an intensity of 65, 70, 80, or 85 dB. Results showed a left ear advantage (LEA) for the 65 dB mask and a right ear advantage for the 85 dB mask, but only after two testing sessions. The possible existence of a generalized right ear bias that might affect the observed LEA for non-verbal tasks is discussed. Alternative explanations and limitations of the present experiment are also presented.     

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.     

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.     

Psychoticism, creativity and dichotic shadowing

Thirty Ss were presented with pairs of words simultaneously under the instruction to shadow one ear while ignoring the other (the Focused Attention condition) or to shadow one ear while attempting to remember the other (the Divided Attention condition). Ss also completed the Eysenck Personality Questionnaire and two tests of creativity from the Wallach and Kogan battery. It was hypothesized that Ss high on EPQ Psychoticism and on creativity should make more shadowing errors of omission and intrusion. Creative Ss made significantly more errors of intrusion under the divided attention condition, but Ss scoring high on the Similarities subtest showed significantly fewer errors in the Focussed Attention condition. An ‘impulsivity’ interpretation of the data is tentatively advanced, and it is shown how this interpretation may explain a number of the anomalous findings in the psychoticism literature.     

Manipulation of voice onset time during dichotic listening

The manipulation of voice onset time (VOT) during dichotic listening has provided novel insights regarding brain function. To date, the most common design is the utilisation of four VOT conditions: short-long pairs (SL), where a CV syllable with a short VOT is presented to the left ear and a CV syllable with a long VOT is presented to the right ear as well as long-short (LS), short-short (SS) and long-long (LL) pairs. Rimol, Eichele, and Hugdahl (2006) first reported that in healthy adults SL pairs elicit the largest REA while, in fact, LS pairs elicit a significant left ear advantage (LEA). This VOT effect was replicated by Sandmann et al. (2007). A study of children aged 5-8years of age has shown a developmental trajectory whereby long VOTs gradually start to dominate over short VOTs when LS pairs are being presented under dichotic conditions (Westerhausen, Helland, Ofte, & Hugdahl, 2010). Two studies have investigated attentional modulation of the VOT effect in children and adults. The converging evidence from these studies shows that at around 9years of age children lack the adult-like cognitive flexibility required to exert top-down control over stimulus-driven bottom-up processes (Andersson, Llera, Rimol, & Hugdahl, 2008; Arciuli, Rankine, & Monaghan, 2010). Arciuli et al. further demonstrated that this kind of cognitive flexibility is a predictor of proficiency with complex tasks such as reading. A review of each of these studies, the possible mechanisms underlying the VOT effect and directions for future research are discussed.     

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.     

Attentional strategies in dichotic listening

A person can attend to a message in one ear while seemingly ignoring a simultaneously presented verbal message in the other ear. There is considerable controversy over the extent to which the unattended message is actually processed. This issue was investigated by presenting dichotic messages to which the listeners responded by buttonpressing (not shadowing) to color words occurring in the primary ear message while attempting to detect a target word in either the primary ear or secondary ear message. Less than 40% of the target words were detected in the secondary ear message, whereas for the primary ear message (and also for either ear in a control experiment), target detection was approximately 80%. Furthermore, there was a significant negative correlation between buttonpressing performance and secondary ear target-detection performance. The results were interpreted as being inconsistent with automatic processing theories of attention.     

Component problems in dichotic listening

The experiments reported examined monitoring for semantically defined targets whilst concurrently shadowing (Experiment I) or listening silently (Experiment II). The word lists for monitoring were either visual or auditory. Monitoring and shadowing accuracy showed less interference when presentation was bimodal than when it was dichotic. However, monitoring latency and recognition memory for shadowed material did not show this effect. It is argued that these data reveal the existence of a number of different sources of potential difficulty in dichotic listening situations and the nature of these is discussed.