Attentional strategies in dichotic listening.

Describes 2 experiments in which a total of 48 college students heard series of 3 dichotic word-digit pairs and were instructed to recall them either by ears or by types. Recall instructions were given before each block of 12 series, before each individual series, or after each series. With preinstruction, serial position effects were rather flat for the 1st-reported channel but showed a marked recency effect for the 2nd-reported channel, suggesting that the Ss attended mainly to the lst channel. With postinstruction, serial position effects were parallel for the 2 channels. Results were practically the same whether channels represented ears or types, suggesting that attention played the same role in each case. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Laterality effects for musical structure processing: A dichotic listening study.

Objective: Our study investigated hemispheric lateralization for musical structure processing using a dichotic listening paradigm with music and speech. Method: Eight chord sequences and 8 spoken syllable sequences were simultaneously presented, each to 1 ear. For the musical sequences, the final chord was expected (i.e., tonic) or less expected (i.e., subdominant). In addition to tonal function, which was task irrelevant, we manipulated the final syllable and the final timbre of the sequences for the experimental task: Participants were asked to identify the final syllable (/di/, /du/) or the timbre of the final chord (Timbre A or B). Results: Our experiment revealed a left-ear advantage for the tonal function effect on spoken syllable identification. For syllables presented to the right ear, identification was faster when the final chord of the musical sequence was a tonic chord rather than a subdominant chord (i.e., musical sequences presented to the left ear). Conclusions: The present finding extends the effect of musical structure previously observed for sung and visual syllable processing to spoken syllable processing. It further suggests a right-hemispheric specialization for the processing of musical structures in healthy listeners, as previously reported for split-brain patients (Tramo & Bharucha, 1991). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the perception of sarcasm in dichotic listening.

The purpose of the present study was to investigate the processing of sincere and sarcastic statements by the cerebral hemispheres. Forty right-handed students were asked to localize sincere and sarcastic statements presented dichotically. Participants either indicated the ear that perceived the sarcastic statement or the ear that perceived the sincere statement in counterbalanced blocks of trials. As expected, results revealed a left ear advantage for sarcastic statements and a right ear advantage for sincere statements. In addition, participants showed faster response time when localizing targets (both sarcastic and sincere) to the left ear compared to the right. Finally, a significant negative correlation between laterality effects in the two tasks provided support for causal hemispheric complementarity. Results are discussed with reference to the contribution of the right and left hemispheres to language processing. Their implications for models of sarcasm perception are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Processing capacity and switching attention in dichotic listening.

Describes 4 experiments with 82 undergraduates which indicate that (a) switching attention in a dichotic listening task requires processing capacity, and (b) increasing encoding difficulty reduces the amount of switching in a free recall dichotic listening task. Results are discussed in terms of a limited capacity processor model which contends that switching attention, encoding, and sustaining material all require processing capacity and that the S's strategy regarding switching attention is determined by the capacity available after capacity requirements for encoding are met. (French summary) (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Endogenous and exogenous control of attention in dichotic listening.

Dichotic listening to verbal stimuli results in a right ear advantage (REA), indicating a left hemisphere processing superiority. The magnitude of the REA can be modulated by instructions to direct attention to the left or right ear stimulus. A previous study from our laboratory showed that presenting a prime syllable before the presentation of the dichotic syllables increases reports of the nonprimed syllable, apparently a negative priming effect that inhibits attention to the distracting prime representation. The present study combined attention instruction and priming, making up a 3 × 3 factorial design. The prime stimulus was a single consonant-vowel syllable presented binaurally just before onset of the dichotic consonant-vowel syllables. Results showed that both instructions and priming manipulations had an effect on which dichotic stimulus was selected. There was also a significant interaction between attention instruction and priming manipulation, indicating that the mechanism for instructed attention and the mechanism for negative priming work on the same level of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retrieval tags and order of report in dichotic listening.

To explain the effects of varying the rate of presentation on order of report in dichotic listening, a retrieval tag model must consider 2 kinds of tag, side and temporal position, and must include a mechanism sensitive to the rate manipulation to alter the relative usefulness of the 2 tags. 2 absolute judgment experiments with undergraduates (N = 32) yielded no evidence that the relative usefulness of the tags is altered passively by a rate manipulation. Results are interpreted as evidence against a model which considers only retrieval operations, and an alternate model encorporating both attention operations and retrieval operations is suggested. (French summary) (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reduced lateralization in verbal dichotic listening in adolescent psychopaths.

One possible explanation for previous findings of abnormal linguistic processing in psychopaths is that they are less lateralized for verbal processes. This study tests the hypothesis that adolescent psychopaths show evidence of reduced lateralization on a verbal dichotic listening task. Four self-report and behavioral measures of psychopathy were used to define psychopathy using cluster analytic techniques in 40 juvenile offenders aged 13 to 18 years. Psychopaths were found to have reduced ear asymmetries relative to nonpsychopaths, a result indicating reduced lateralization for verbal material. The effect does not appear to be mediated by group differences in age, ethnic background, IQ, overall performance, left-handedness, selective attention to one ear, or interhemispheric transfer deficits. This result suggests that the previous finding by R. D. Hare and L. M. McPherson (see record 1984-23362-001) is robust, provides some preliminary validity for the assessment of psychopathy before age 18, and indicates initial support for the utility of cluster analytic techniques in the assessment of psychopathy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemisphere-specific interference in dichotic listening: Task variables and individual differences.

In Exps I and II, 214 right-handed college students were required to identify dichotically presented CV syllables with either no concurrent memory (CM) load or with a CM load of 6 low-imagery nouns. Based on performance on their initial set of no-load trials, Ss were assigned to either a right-, left-, or no-ear advantage (REA, LEA, or NEA) group. Results for the REA group were similar to the results of previous studies of visual laterality and concurrent activity: Introducing a CM load of 6 words reduced recognition of right-ear CVs but not left-ear CVs. Furthermore, these effects persisted across 2 blocks of no-load and memory-load trials. This Memory Load?×?Ear interaction was weaker in the NEA group and tended to be reversed in the LEA group. About 10% of Ss showed a consistent LEA for CV recognition, and, for these Ss, introducing a CM load of 6 words reduced recognition of left-ear CVs but did not change the recognition of right-ear CVs. Again, these effects persisted across 2 blocks of no-load and memory load trials. Exp III (48 Ss) was similar to Exps I and II except that the CM task involved nonsense shapes that could probably be processed by either hemisphere. Introducing this concurrent nonverbal memory task did not reduce the recognition of either right- or left-ear CVs. Results indicate that the verbal nature of the concurrent task appears to be critical, as in previous visual laterality experiments. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in dichotic listening with categorized word lists.

Two experiments examined the effects of blocking of word lists (grouped by semantic category membership or randomly ordered) on the dichotic listening performances of 48 2nd and 48 5th graders. For Exp I, shadowing and retention scores were obtained for groups of Ss representing the 4 combinations of blocked and random word lists for targets and distractors. Blocking of distractor lists led to better shadowing scores for 2nd graders. When word pairs were matched by categories in Exp II, 2nd graders who heard blocked lists recognized fewer target words (in retention tests) than did those who heard randomly ordered word lists. Results are interpreted in the context of variables that affect the shadowing performances of younger children and developmental differences in encoding strategies. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance of paranoid schizophrenics on a dichotic listening task.

Used 15 adult normals and 15 institutionalized paranoid schizophrenics in a dichotic listening task within a 2 (Groups) * 2 (Associated or Unassociated Word List) * 2 (Presentation Rate) design, with repeated measures on the last 2 variables. Presentation rates were either 1 or 3 sec. Dependent variables were word recall, intrusion errors, and strategy use and accuracy. Normals recalled significantly more information than paranoid schizophrenics under all memory conditions and had significantly fewer total intrusion errors. For both groups, information recall was significantly better under the associative conditions (particularly associative structure, 3-sec presentation rate). Under the varying structure conditions, paranoid schizophrenics did not employ optimal strategies with the same frequency or degree of accuracy as normals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Baseline asymmetries in brain electrical activity predict dichotic listening performance.

Forty-four right-handed participants were assessed on 2 occasions 6 weeks apart on electrophysiological measures of activation asymmetry derived from spectral estimates of electroencephalogram (EEG) alpha power in homologous scalp electrodes. Approximately 4 months following the final EEG assessment. participants were administered a dichotic listening CV-syllables task. Overall, participants exhibited a highly significant right-ear advantage. Differences among individuals in ear asymmetry were predicted by the earlier recorded electrophysiological data. Participants with greater activation in left-sided posterior temporal and parietal regions showed a larger right-ear advantage. In addition, a larger right-ear advantage was predicted by right-sided prefrontal activation. These data indicate that some of the variance in dichotic listening performance can be explained by dispositional activation asymmetries and is associated with a complex pattern of posterior and anterior activation asymmetries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A second testing of paranoid schizophrenics on a dichotic listening task

Data from 15 adult institutionalized Ss tested twice over a 1-yr period show a slight deterioration in organizational abilities for short-term memory task performance over the succeeding times of measurement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory attention in hyperactive children: Effects of stimulant medication on dichotic listening performance.

Administered dichotic digit tasks requiring free report and selective listening, respectively, to 20 6–16 yr old hyperactive children. Ss received methylphenidate before 2 experimental sessions and a placebo before 2 control sessions. The stimulant did not improve free-report performance significantly; rather it facilitated or impaired performance, depending on how it affected the order in which stimuli were reported. Similarly, medication had no effect on overall selective-listening performance, but it increased the difficulty of switching attention from one ear to the other. Results demonstrate that stimulants may act to maintain selective attention and to inhibit channel switching. Listening asymmetry, that is, right-ear superiority, was influenced by task variables but not by stimulant medication. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the corpus callosum in dichotic listening: A combined morphological and diffusion tensor imaging study.

The objective of the present study was to examine the role of the corpus callosum (CC) in dichotic listening. For this purpose, 40 right-handed healthy male participants were assessed with morphological and diffusion tensor imaging, which yielded macrostructural (midsagittal area) and microstructural (mean diffusion, fractional anisotropy) measures of the total CC and predefined subregions. Applying the standard consonant-vowel Bergen Dichotic Listening Test (including 3 different attentional instructions), the authors found dichotic listening performance to be substantially related to the integrity of the CC at both macro- and microstructural levels. Results indicate a dual role of the CC; it is relevant not only for the stimulus-driven (bottom-up) transfer of left-ear input to the left hemisphere but also for its attentional (top-down) modulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic processing and memory for attended and unattended words in dichotic listening: Behavioral and electrophysiological evidence.

Thirty-two Ss studied words presented to 1 ear, while ignoring a concurrent word list presented to the opposite ear. The N400 component of the event-related potentials elicited by attended words was modulated by semantic priming between successive words. The N400 elicited by unattended words was insensitive to semantic manipulation. Recognition memory was better for attended than for unattended words. However, the percentage of false positives was elevated equally for lures that were semantically related to "old" words, whether they had been attended or unattended. Words that were initially attended induced similar repetition effects in a lexical decision task as words that were initially unattended. Hence, both attended and unattended words are semantically processed and activate semantic representations. However, attended words form traces that are subsequently more available to conscious recollection than unattended words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lateralization of receptive language in preschoolers: Test–retest reliability in a dichotic listening task.

On 2 occasions dichotic digit tapes were presented to 29 right-handed children (aged 33–65 mo). Results indicate that the dichotic listening tasks yielded measures with sufficient test–retest stability to permit reliable group comparisons, but that such indices may differ in terms of their contamination by sample-specific distributions of ability levels. It is suggested that conclusions not be drawn from such measures unless different indices of laterality show converging results and that when groups are compared, investigators include tabulations of both the difference and accuracy scores in their results. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of method of recall on performance in the dichotic listening task.

Reports 2 experiments with 100 undergraduates in which Ss were required to recall dichotically presented digits (3/1/2-span) either vocally or in writing. It was found that items in the 1/2-span reported 2nd were recalled significantly more accurately with written as compared with vocal recall. Data suggest that the differential accuracy of recall of the items in the 2 1/2-spans, which is normally reported, is attributable, partially at least, to interference at output produced by the vocalization of items in the 1st 1/2-span. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Allocation of attention in dichotic listening: Differential effects on the detection and localization of signals.

In 2 dichotic listening experiments, 96 normal right-handed adults attended selectively to the left and right ear and divided their attention equally between both ears. Participants listened for specified targets and reported the ear of entry. The material consisted of pairs of consonant–vowel syllables in Experiment 1 and pairs of rhyming consonant–vowel–consonant words in Experiment 2. Both experiments yielded a right-ear advantage for detection and for localization. Attention instructions had no effect on detection. However, focusing attention on 1 ear increased the number of targets attributed to that ear while decreasing the number of targets attributed to the opposite ear. The dissociation between detection and localization indicates that volitional shifts of attention influence late (response selection) processes rather than early (stimulus identification) processes. Selective-listening effects can be accounted for by a 2-stage model in which a fixed input asymmetry is modulated by a biased selection of responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of aphasic and non-brain-injured adults on a dichotic CV-syllable listening task

A dichotic CV-syllable listening task was administered to a group of eleven non-brain-injured adults and to a group of eleven adult aphasics. The results of this study may be summarized as follows: 1)The group of non-brain-injured adults showed a slight right ear advantage for dichotically presented CV-syllables. 2)In comparison with the control group the asphasic group showed a bilateral deficit in response to the dichotic CV-syllables, superimposed on a non-significant right ear advantage. 3) The asphasic group demonstrated a great deal of intersubject variability on the dichotic task with six aphasics showing a right ear preference for the stimuli. The non-brain-injured subjects performed more homogeneously on the task. 4) The two subgroups of aphasics, a right ear advantage group and a left ear advantage group, performed significantly different on the dichotic listening task. 5) Single correct data analysis proved valuable by deleting accuracy of report for an examination of trials in which there was true competition for the single left hemispheric speech processor. These results were analyzed in terms of a functional model of auditory processing. In view of this model, the bilateral deficit in dichotic performance of the asphasic group was accounted for by the presence of a lesion within the dominant left hemisphere, where the speech signals from both ears converge for final processing. The right ear advantage shown by one asphasic subgroup was explained by a lesion interfering with the corpus callosal pathways from the left hemisphere; the left ear advantage observed within the other subgroup was explained by a lesion in the area of the auditory processor of the left hemisphere.