Attentional set in pure- versus mixed-lists in a dichotic listening paradigm

An experiment was designed to assess the contribution of attentional set to performance on a forced choice recognition task in dichotic listening. Subjects were randomly assigned to one of three conditions: speech sounds composed of stop consonants, emotional nonspeech sounds, or a random combination of both. In the groups exposed to a single class of stimuli (pure-list), a REA (right ear advantage) emerged for the speech sounds, and a LE (left ear advantage) for the nonspeech sounds. Under mixed conditions using both classes of stimuli, no significant ear advantage was apparent, either globally or individually for the speech and nonspeech sounds. However, performance was more accurate for the left ear on nonspeech sounds and for the right ear for speech sounds, regardless of pure versus mixed placement. The results suggest that under divided attention conditions, attentional set influences the direction of the laterality effect.     

Hemispheric Differences in the Recognition of Environmental Sounds

ABSTRACT— Recent work has found support for two dissociable and parallel neural subsystems underlying object and shape recognition in the visual domain: an abstract-category subsystem that operates more effectively in the left cerebral hemisphere than in the right, and a specific-exemplar subsystem that operates more effectively in the right hemisphere than in the left. Evidence of this asymmetry has been observed for linguistic stimuli (words, pseudoword forms) and nonlinguistic stimuli (objects). In the auditory domain, we previously found hemispheric asymmetries in priming effects using linguistic stimuli (spoken words). In the present study, we conducted four long-term repetition-priming experiments to investigate whether such hemispheric asymmetries would be observed for nonlinguistic auditory stimuli (environmental sounds) as well. The results support the dissociable-subsystems theory. Specificity effects were obtained when sounds were presented to the left ear (right hemisphere), but not when sounds were presented to the right ear (left hemisphere). Theoretical implications are discussed.     

Hemispheric differences are found in the identification,but not the detection,of low versus high spatial frequencies

The processing of sine-wave gratings presented to the left and right visual fields was examined in four experiments. Subjects were required either to detect the presence of a grating (Experiments 1 and 2) or to identify the spatial frequency of a grating (Experiments 3 and 4). Orthogonally to this, the stimuli were presented either at threshold levels of contrast (Experiments 1 and 3) or at suprathreshold levels (Experiments 2 and 4). Visual field and spatial frequency interacted when the task required identification of spatial frequency, but not when it required only stimulus detection. Regardless of contrast level (threshold, suprathreshold), high-frequency gratings were identified more readily in the right visual field (left hemisphere), whereas low-frequency gratings showed no visual field difference (Experiment 3) or were identified more readily in the left visual field (right hemisphere) (Experiment 4). Thus, hemispheric asymmetries in the processing of spatial frequencies depend on the task. These results support Sergent’s (1982) spatial frequency hypothesis, but only when the computational demands of the task exceed those required for the simple detection of the stimuli.     

An investigation of bilateral asymmetries in electrodermal activity

Research in cerebral laterality supports the idea that functional differences between the left and right hemispheres exist with respect to cognitive style and perceptual ability. Related research, which has examined autonomic nervous system (ANS) correlates of cerebral laterality, suggests that a component of the ANS, electrodermal activity (EDA), is also lateralized. Some findings in the literature report the occurrence of bilateral asymmetries in phasic and tonic EDA as a function of a left or right hemisphere preference for information processing. This experiment used normal male subjects who were either left or right movers in a test of Conjugate Lateral Eye Movement (CLEM). This selection procedure served to maximize a subject’s preference for either a right or left hemisphere mode of information processing. Bilateral EDA was recorded continuously while subjects performed a visual recognition task using word (left hemisphere) and shape (right hemisphere) stimuli. The data do not support the contention that performance on a procedure chosen to selectively activate a given hemisphere elicits asymmetric tonic and/or phasic EDA. The results show no significant difference in the frequency of elicited skin conductance responses under either of the experimental conditions. Bilateral tonic EDA rose continuously over time and did not vary in either hand as a function of task. The present results fail to offer support for either of the hypotheses which argue for I) increased contralateralexcitation with selective hemispheric activation, or 2) increased contralateralinhibition of the EDR with hemispheric arousal.     

Lateral specialization and social-verbal development in preschool children

Forty-two 2 1/2- to 5 1/2-year-old children's social and verbal behaviors were observed during free play in a preschool. A test measuring lateral specialization of verbal function and a standardized psychometric test of verbal ability were also administered. Analysis of variance indicated that the right ear (left hemisphere) is predominant in processing verbal stimuli in children as young as 2 1/2. Multiple regression analyses revealed significant relations between the right ear accuracy score for dichotically presented verbal stimuli and both psychometrically measured verbal ability and a social-verbal factor score derived from play behavior. After the increase related to age was statistically partialled out from both verbal ability and social-verbal scores, verbal expression, length of verbal utterances, time spent in conversation, and peer social interactions increased and parallel play decreased as a function of right ear (left hemisphere) accuracy for verbal stimuli. The relationship between left ear (right hemisphere) accuracy scores for verbal stimuli and social-verbal behavior, however, was not linear. Very high and very low levels of left ear recall predicted an increase in the frequency of parallel play and low social-verbal behavior while moderate levels of left ear accuracy scores predicted the reverse.     

The role of spatial complexity in the perception of speech and pure tones in dichotic listening

Ear advantages for CV syllables were determined for 28 right-handed individuals in a target monitoring dichotic task. In addition, ear dominance for dichotically presented tones was determined when the frequency difference of the two tones was small compared to the center frequency and when the frequency difference of the tones was larger. On all three tasks, subjects provided subjective separability ratings as measures of the spatial complexity of the dichotic stimuli. The results indicated a robust right ear advantage (REA) for the CV syllables and a left ear dominance on the two tone tasks, with a significant shift toward right ear dominance when the frequency difference of the tones was large. Although separability ratings for the group data indicated an increase in the perceived spatial separation of the components of the tone complex across the two tone tasks, the separability judgment ratings and the ear dominance scores were not correlated for either tone task. A significant correlation, however, was evidenced between the laterality measure for speech and the judgment of separability, indicating that a REA of increased magnitude is associated with more clearly localized and spatially separate speech sounds. Finally, the dominance scores on the two tone tasks were uncorrelated with the laterality measures of the speech task, whereas the scores on the tone tasks were highly correlated. The results suggest that spatial complexity does play a role in the emergence of the REA for speech. However, the failure to find a relationship between speech and nonspeech tasks suggest that all perceptual asymmetries observed with dichotic stimuli cannot be accounted for by a single theoretical explanation.     

Hemispheric specialization for processing of visually presented verbal and spatial stimuli

Two “same-different” reaction time experiments, analogous in task demands made on the S, were designed to test laterality differences in. perception. Ten normal right-handed Ss performed a verbal task in which they decided whether or not two three-letter words belonged to the same conceptual class. Ten different Ss performed a spatial task in which they decided whether two 16-cell matrices with 3 blackened cells were identical. Reaction times were found to be sensitive to laterality differences in perception. Verbal stimuli were processed faster when presented in the right visual field, and thus projected directly to the left cerebral hemisphere; spatial stimuli were processed faster when presented in the left visual field, and thus projected directly to the right cerebral hemisphere. These results were analyzed in terms of implications regarding hemispheric asymmetries for processing of verbal and spatial material and the nature of interhemispheric transfer of information.     

Hemisphere differences in an auditory Stroop test

In an auditory Stroop test, right-handed subjects were required to judge the pitch of the following stimuli: two pure tones, one at a high frequency and one at a low frequency; two congruent words, “high,” sung at the high frequency, and “low,” sung at the low frequency; and two noncongruent words, “high” at low frequency and “low” at high frequency. A sequence of these stimuli was presented monaurally first to one ear, and then to the other. The Stroop effect (the difference between mean RT to congruent words, and mean RT to noncongruent words) was larger for right ear (left hemisphere) presentation. The same experiment was repeated dichotically with a competing message presented to the opposite ear. Again, the Stroop effect was larger for the right ear, and the ear differences were slightly more marked. The result is interpreted as reflecting hemispheric specialization for linguistic and nonlinguistic processing and a model of Stroop conflict in which response competition varies with the relative availability of the conflicting response.

     

Motivation, affect, and hemispheric asymmetry: power versus affiliation

In 4 experiments, the authors examined to what extent information related to different social needs (i.e., power vs. affiliation) is associated with hemispheric laterality. Response latencies to a lateralized dot-probe task following lateralized pictures or verbal labels that were associated with positive or negative episodes related to power, affiliation, or achievement revealed clear-cut laterality effects. These effects were a function of need content rather than of valence: Power-related stimuli were associated with right visual field (left hemisphere) superiority, whereas affiliation-related stimuli were associated with left visual field (right hemisphere) superiority. Additional results demonstrated that in contrast to power, affiliation primes were associated with better discrimination between coherent word triads (e.g., goat, pass, and green, all related to mountain) and noncoherent triads, a remote associate task known to activate areas of the right hemisphere.     

Hemispheric differences in specificity effects in talker identification

In the visual domain, Marsolek and colleagues (1999, 2008) have found support for two dissociable and parallel neural subsystems underlying object and shape recognition: an abstract-category subsystem that operates more effectively in the left cerebral hemisphere (LH), and a specific-exemplar subsystem that operates more effectively in the right cerebral hemisphere (RH). Evidence of this asymmetry has been observed in priming specificity for linguistic (words, pseudoword forms) and nonlinguistic (objects) stimuli. In the auditory domain, the authors previously found hemispheric asymmetries in priming effects for linguistic (spoken words) and nonlinguistic (environmental sounds) stimuli. In the present study, the same asymmetrical pattern was observed in talker identification by means of two long-term repetition-priming experiments. Both experiments consisted of a familiarization phase and a final talker identification test phase, using sentences as stimuli. The results showed that specificity effects (an advantage for same-sentence priming, relative to different-sentence priming) emerged when the target stimuli were presented to the left ear (RH), but not when the target stimuli were presented to the right ear (LH). Taken together, this consistent asymmetrical pattern of data from both domains-visual and auditory-may be indicative of a more general property of the human perceptual processing system. Theoretical implications are discussed.     

汉语普通话声调加工的右耳优势及其机理：一项双耳分听的研究

采用双耳分听的任务探讨了汉语普通话声调加工的右耳优势问题,并引进反应手的因素,探讨了汉语声调加工的右耳优势的机制。结果表明,汉语母语被试对普通话声调的加工存在右耳、左脑优势,但这种优势是相对的,右脑也具备加工声调信息的能力,结果支持了直接通达模型。     

Is there parallel and independent hemispheric processing of intonational and phonetic components of dichotic speech stimuli?

The possibility of hemisphere interaction in the processing of spoken language was studied in two dichotic listening experiments. The stimulus material consisted of six CV syllable triplets each spoken with each one of six intonation contours. In Experiment I, 15 aphasic patients, 8 patients with unilateral right hemisphere lesions, and 10 normal controls were asked to identify the four components of a dichotic item from a multiple-choice (MC) set comprising all possible CV triplets and intonation contours. In Experiment II, 30 normal subjects were required to identify either the right or left ear stimulus alone from an MC set comprising the right and left ear stimulus together with the two wrong combinations of right ear CV triplet with left ear intonation and vice versa. It is concluded from the results that the left hemisphere is capable of processing both phonetic and intonational information and that there is neither the necessity nor the tendency for right hemisphere participation in the perception of spoken language.     

The effects of attention on ear advantages in dichotic listening to words and affects

This study examined the effects of attention on ear advantages using dichotic listening to words and affects, a focused-attention paradigm. We compared the mixed condition, in which attention is switched between the ears in each trial, to the blocked condition, in which attention is directed to one ear for an entire block of trials. Results showed a decreased right ear advantage for word processing only in the mixed condition and an increased left ear advantage for emotion processing in both attention conditions for hits index. The mixed condition showed smaller laterality effects than the blocked condition for words with respect to hits index, while increasing right ear predominance for intrusions. The greater percentage of intrusions in the right ear for the word task and in the mixed condition suggests that the right ear (left hemisphere) is most vulnerable to attention switching. We posit that the attention manipulation has a greater effect on word processing than on emotion processing and propose that ear advantages reflect a combination of the effects of attentional and structural constraints on lateralisation.     

Performance and reaction times in monaural localization of first names in the horizontal plane

Many studies have been conducted to measure monaural azimuthal sound localization performance with different sounds varying in frequency and complexity, but few have used linguistic stimuli. The present experimental design used subjects' first names in a monaural azimuthal localization task. Analysis of response accuracy showed that subjects are not more accurate in localizing their own first name than in localizing other first names and that there was no significant advantage of one ear over another. Reaction times were shorter when the subjects localized their own first name than when they localized any other first names and there was no significant ear advantage, but localizing other first names took more time with the right than with the left ear. All stimuli were better and more quickly localized on the side of the open ear, and there was no difference in acuity or velocity of localization with the two different speaker voices used. These results suggest that first names are processed through the controlateral auditory pathway and can be analyzed in the right hemisphere.     

Lateralisation of emotions: evidence from pupil size measurement

The way our brain processes emotional stimuli has been studied intensively. One of the main issues still under debate is the laterality of valence processing. Herein, we employed the fact that pupil size increases under conditions of higher mental effort and during emotional processing, in order to contrast three proposed hypotheses in the field. We used different manual response mapping for emotional stimuli: Participants responded with their right hand for positive and with their left hand for negative facial expressions, or vice versa. The hands position was either regular (Experiment 1) or crossed (Experiment 2) in order to rule out a “spatial-valence association” alternate explanation. A third experiment was conducted by employing a passive viewing procedure of peripheral emotional stimuli. In the first two experiments, pupil size was larger when participants responded to positive stimuli with their left hand and to negative with their right hand, compared with the opposite mapping. Results of Experiment 3 strengthen the findings of Experiments 1 and 2. These findings provide significant psychophysiological evidence for the valence hypothesis: Processing positive stimuli involves the left hemisphere, while processing negative stimuli involves the right hemisphere. These results are discussed in relation to contemporary theories of emotion processing.     

Lateralization of auditory rhythm length in temporal lobe lesions

In the visual modality, short rhythmic stimuli have been proven to be better processed (sequentially) by the left hemisphere, while longer rhythms appear to be better (holistically) processed by the right hemisphere. This study was set up to see if the same holds in the auditory modality. The rhythm task as originally designed by Seashore was computerized and is part of the Fepsy Neuropsychological battery. This task was performed by 85 patients with intractable temporal lobe epilepsy (left TLE = 32; right TLE = 53) enrolled in the Dutch Collaborative Epilepsy Surgery Program. They performed the task before and 6 months after surgery. The task consists of 30 pairs of rhythmic patterns in 3 series of 10 items. The series contains patterns of 5, 6, or 7 notes. The purpose is to indicate whether the two patterns are the same or different. Reaction times are also measured. If the hypothesis is true, the short-item sequence will be better processed by patients with right temporal lobe epilepsy (nonimpaired left temporal lobe), the longer sequence will be better processed by the left temporal epilepsy group (nonimpaired right temporal lobe). No overall laterality effect on rhythm perception could be found and no difference was found between both test moments. IQ did not correlate with rhythm performance. However, there was an interaction effect of laterality and rhythm length on performance and reaction time. This effect can be explained by the increase after the operation of the score of the left focus group and a decrease in the right focus group on the longer rhythms. This effect was somewhat less strong in the reaction times: a clear tendency for faster reaction times after surgery in the left and longer reaction times in the right focus group. The effect could not be explained for by the difference in extent of resection in either temporal lobe. This study showed that memory for and discrimination of auditory rhythm is dependent on which hemisphere is used in processing. The effect could be demonstrated for the right hemisphere, which uses a holistic processing of stimuli, which outperforms the left in rhythms consisting of a long sequence. In left temporal resections an improvement occurs on the longer rhythms and in right temporal resections the performance on the longest rhythms decreases.     

Cerebral hemispheric involvement in the acquisition of new phonetic categories

This study was concerned with the involvement of the cerebral hemispheres in the acquisition of perceptual skill with novel speech sounds. Two groups of eight subjects rated on three occasions the dissimilarity of pairs of Mandarin Chinese speech sounds varying on voicing and aspiration, presented to the left or right ear with contralateral noise. The experimental group received listening experience with long passages of Mandarin containing the target sounds. Multidimensional scaling analysis of dissimilarity ratings indicated that listening experience leads to increased perceptual differentiation of phonetic categories drawn from a language unfamiliar to the listener. This improvement occurred sooner with presentation of the target sounds to the right hemisphere than to the left if the phonological contrast was along the voicing dimension. Improvement in the perception of stimuli varying on aspiration occurred in right ear presentations only. This finding supports the position that speech perception mechanisms at the feature level may be distributed asymmetrically across the hemispheres.     

Lateralization of lexical codes in auditory word recognition

Three experiments examined the lateralization of lexical codes in auditory word recognition. In Experiment 1 a word rhyming with a binaurally presented cue word was detected faster when the cue and target were spelled similarly than when they were spelled differently. This orthography effect was larger when the target was presented to the right ear than when it was presented to the left ear. Experiment 2 replicated the interaction between ear of presentation and orthography effect when the cue and target were spoken in different voices. In Experiment 3, subjects made lexical decisions to pairs of stimuli presented to the left or the right ear. Lexical decision times and the amount of facilitation which obtained when the target stimuli were semantically related words did not differ as a function of ear of presentation. The results suggest that the semantic, phonological, and orthographic codes for a word are represented in each hemisphere; however, orthographic and phonological representations are integrated only in the left hemisphere.     

Information processing and speech lateralization in learning-disabled children

The relationship between information processing and speech lateralization was investigated in learning-disabled children. The Kaufman Assessment Battery for Children (K-ABC) assessed simultaneous and successive processing while a dichotic listening paradigm with free recall and directed attention conditions assessed speech lateralization. A three-factor ANOVA design conducted on the dichotic data revealed that normal children demonstrated stronger right ear advantage (REA); whereas learning-disabled showed weaker right ear advantage. Further, lambda analyses conducted on individual subjects revealed that the learning-disabled did not demonstrate the REA, were not biased attenders, and did not get more right ear than left ear items when attention was directed to one ear. Multiple-regression analysis was used to predict sequential processing from the dichotic data for both groups. Learning-disabled children demonstrated a substantial deficit in sequential processing as compared to normal children. These results indicate that learning-disabled children may not have adequate cerebral lateralization of receptive speech processes, shift their attention more readily, and are more inadequate in sequential processing that presumably subserves language functioning. Perhaps learning-disabled children have deficiencies of processor capacity of salient areas of the left (language) hemisphere.     

The perception of stress and lateralization of prosody

Three separate dichotic listening tasks were run to determine ear superiority for stress identification. When subjects were asked to identify stress placement in real word minimal stress pairs (hótdog vs. hot dóg), they demonstrated a right ear superiority. When these tokens were filtered so that phonetic and semantic information was eliminated and only the stress pattern remained, a different group of subjects showed a left ear advantage. Finally, with nonsense word counterparts to word stress pairs (bótgog vs. bot góg) preserving phonetic information but lacking semantic content, no ear asymmetry was found. These results suggest that as the linguistic significance of the stimuli is reduced, thereby lessening the linguistic function of stress, there is a less dominant involvement of the left hemisphere in stress processing. Results are discussed in relation to a theory of a functional integration of prosodic and segmental speech components that is paralleled by a working partnership of left and right hemisphere.