Asymmetries of selective listening and attention switching in children.

Administered a selective listening task to 155 normal right-handed 3–12 yr old children. The stimuli consisted of dichotic digits, ranging from single pairs to strings of 4 pairs/trial. Each S attempted to focus attention on 1 ear for 8 practice trials and 28 test trials before switching attention to the opposite ear. Separate analyses of correct responses and intrusion errors yielded almost identical results: There was a significant right-ear advantage (REA) and a developmental increase in overall performance, but there was no developmental change in degree of asymmetry. The REA increased with increasing list length, but independent analyses for each list length failed to reveal any developmental changes in REA. Listening asymmetry was influenced markedly by the order in which the ears were monitored; Ss of all ages had difficulty in switching attention from right ear to left. Results support the developmental invariance hypothesis of cerebral lateralization and demonstrate that auditory asymmetry is not merely a direct reflection of some fixed structural asymmetry in the brain. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric specialization and ear advantages in processing speech.

Reviews research on the hemispheric asymmetry model of relative ear advantages in the processing of auditory stimuli. Physiological studies of activation of the hemispheres in humans support left-hemisphere speech-processing specialization and contralateral sound field dominance. Electrophysiological studies in animals, effects of commissurotomy, hemispherectomy, and unilateral temporal lobe lesions on dichotic performance in humans, as well as stimulus dominance effects in intact Ss indicate that the assumption of ipsilateral sensory pathway suppression during competitive stimulation is unwarranted. Dichotic presentation is not necessary to produce a right-ear advantage (REA), and selective attention to one or the other ear frequently tends to alter the magnitude of the REA. A modified structural model that incorporates the effects of directed attention is proposed. (3? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential neural contributions to native- and foreign-language talker identification.

Humans are remarkably adept at identifying individuals by the sound of their voice, a behavior supported by the nervous system’s ability to integrate information from voice and speech perception. Talker-identification abilities are significantly impaired when listeners are unfamiliar with the language being spoken. Recent behavioral studies describing the language-familiarity effect implicate functionally integrated neural systems for speech and voice perception, yet specific neuroscientific evidence demonstrating the basis for such integration has not yet been shown. Listeners in the present study learned to identify voices speaking a familiar (native) or unfamiliar (foreign) language. The talker-identification performance of neural circuitry in each cerebral hemisphere was assessed using dichotic listening. To determine the relative contribution of circuitry in each hemisphere to ecological (binaural) talker identification abilities, we compared the predictive capacity of dichotic performance on binaural performance across languages. Listeners’ right-ear (left hemisphere) performance was a better predictor of binaural accuracy in their native language than a foreign one. This enhanced role of the classically language-dominant left hemisphere in listeners’ native language demonstrates functionally integrated neural systems for speech and voice perception during talker identification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Monaural and binaural story recall by schizophrenic subjects.

P. Green and other investigators have reported that schizophrenic Ss have poorer recall of stories presented to both ears than to the single best ear (binaural deficit) and poorer recall of stories presented to the left ear than to the right ear (monaural asymmetry) than do normal control Ss. These studies are plagued by potential methodological problems, including differences in overall accuracy, which artifactually affect the difference scores, and scoring methods that are vulnerable to systematic bias. In this study, scores of schizophrenic, bipolar, and normal control Ss on the Auditory Comprehension Test were compared. Scoring bias was avoided by the use of blind scoring and a revised scoring manual, and artifactual effects of accuracy were considered in interpreting the results. Contrary to previous findings, the groups did not differ on either monaural asymmetry or binaural deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of three strategies of attention in dichotic monitoring.

Investigated 3 strategies of attention in 108 Ss in 3 age groups (7, 11, and 20 yrs). Ss monitored lists of monaural and dichotic words and responded manually to target words. Target detection rates in unequal division of attention (Exp I) showed that selection of the relevant input improved with age. The degree of attenuation of the irrelevant input was dependent on which ear was being ignored, but this effect interacted with age. The 7-yr-olds could not attend effectively to left-ear items. Exp II simplified the focusing strategy by eliminating response requirements to the irrelevant input. Selectivity improved with this strategy, particularly in 7-yr-olds. Equal division of attention between the 2 ears (Exp III) revealed a constant right-ear advantage in each age group. Differentiation of the 3 voluntary strategies improved between ages 7 and 11. In adults, the 3 strategies were clearly distinguished. Results are interpreted in terms of a multiprocess model of attention: Perceptual factors such as dichotic interaction and hemispheric asymmetry were strategy dependent but not age dependent. Voluntary selective attention was age dependent and affected the degree to which hemispheric asymmetry could be overcome. (25 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)     

Processing of auditory stimuli during auditory and visual attention as revealed by event-related potentials

Auditory event-related brain potentials (ERPs) were recorded during auditory and visual selective attention tasks. Auditory stimuli consisted of frequent standard tones (1000 Hz) and infrequent deviant tones (1050 Hz and 1300 Hz) delivered randomly to the left and right ears. Visual stimuli were vertical line gratings randomly presented on a video monitor at mean intervals of 6 s. During auditory attention, the subject attended to the stimuli in a designated ear and responded to the 1300-Hz deviants occurring among the attended tones. During visual attention, the subject responded to the occasional visual stimuli. ERPs for tones delivered to the attended ear were negatively displaced relative to ERPs elicited by tones delivered to the unattended ear and to ERPs elicited by auditory stimuli during visual attention. This attention effect consisted of negative difference waves with early and late components. Mismatch negativities (MMNs) were elicited by 1300-Hz and 1050-Hz deviants irrespective of whether they occurred among attended or unattended tones. MMN amplitudes were unaffected by attention, supporting the proposal that the MMN is generated by an automatic cerebral discrimination process.     

Recall strategies in three-channel immediate memory.

Digits were spoken through earphones via 3 simultaneous auditory "channels," created by having 1 digit spoken to the left ear only, another to the right ear only, and a third (middle channel) to both ears at once. Also, each channel was spoken by a different voice, a woman's in the middle, and different men's voices to left and right. 18 right-handed and 18 left-handed Ss heard a series of 2 such triplets, with onsets of 1 sec. apart. Ss instructed to report the digits channel by channel recalled as many digits as those instructed to report them triplet by triplet, but Ss who were permitted free recall chose the triplet-by-triplet strategy more often than the channel-by-channel one. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of directed attention on cerebral asymmetries in normal and learning-disabled children.

Using a dichotic listening task employing both undirected and directed attention conditions, cerebral asymmetries were examined in matched populations of 32 normal and 32 learning-disabled (LD) children (ages 7 yrs 6 mo–13 yrs 2 mo). The analysis of recall performance indicated that development was not a significant factor in either group; both the normal and LD Ss showed a right-ear effect, although the LD Ss performed at a degraded level and were unable to demonstrate a right-ear advantage (REA) when attention was directed to the left ear, unlike normal Ss, who produced the REA despite the directed attention conditions. Results suggest that LD children probably do not suffer from developmental delays but rather from a defect in callosal functioning that interferes with their ability to process verbal information simultaneously. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Left hemisphere advantage for classical conditioning to auditory verbal CSs: effects of nonattended extinction

The effects of brain laterality, or hemispheric asymmetry, on electrodermal classical conditioning during both attended and nonattended stimulus conditions were studied. Participants were conditioned to consonant-vowel (CV) syllables during an acquisition, or learning, phase of the experiment. During a subsequent extinction phase, the conditioned stimuli (CS) were presented in a dichotic mode of presentation. Half of the participants attended to the left ear (right hemisphere) during the extinction phase and the other half of the participants attended to the right ear (left hemisphere). The results showed effects of conditioning for all participants during the acquisition phase. During dichotic extinction, the left hemisphere group showed remaining learning effects in both the attended and nonattended conditions, whereas the right hemisphere group demonstrated conditioning only in the attended condition.     

Auditory spatial responses of young guinea pigs (Cavia porcellus) during and after ear blocking.

Tested 30 newborn guinea pigs to determine their ability to approach an auditory stimulus early in development. Observations of the behavior of 1–4 day old Ss in a circular 8-choice maze revealed a pronounced tendency to orient toward and approach a tape-recorded signal of guinea pig vocalizations. The occurrence of approach responses was reduced to chance in Ss tested with one ear occluded by wax ear plugs which attenuated but did not totally eliminate sound. The effect of monaural ear blocks was more severe than binaural blocks, which reflects the importance of binaural cues in the maintenance of approach responses to sound. In a 2nd study with 40 Ss the ability of older animals, 11–31 days of age, was examined. Directional approach responses to sound were also evident at this age, and ear plugs disrupted performance only under monaural conditions. Furthermore, in Ss raised from birth with monaural ear blocks but tested without ear plugs, there was a subsequent disruption of performance for at least 21 days. Results indicate the importance of binaural cues in the development of early auditory spatial reponses and suggest the need for appropriate binaural experience for subsequent localization of sounds. (52 ref) (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)     

The development of auditory strategies of attention.

Investigated focused and divided attention in right-handed children in 2 age groups: 6.5–7.5 and 10–11 yrs. Ss listened to lists of simultaneous word pairs that were monitored for the presence of designated target words. An analysis of correct and incorrect response rates showed that there was a general increase in the efficiency of both attention tasks with age, although selective listening performance improved to a greater extent than divided attention. In focused attention, selecting one input and ignoring another developed at different rates. In divided attention, there was a right ear advantage that remained constant across the 2 age groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory evoked potentials during multichannel selective listening: role of pitch and localization cues

Auditory evoked potentials were recorded from subjects who listened selectively to tone pips arriving over one of three input channels. Their task was to detect occasional target tones of a slightly longer duration. In different runs the three channels were distinguished from one another by (a) pitch cues alone (800, 1,800, and 2,800 Hz), (b) localization cues alone (right ear, midline, ane left ear), and (c) both of these cues conjointly. In all three conditions the direction of attention was reflected in the amplitude of the N1 wave of the evoked potential, which was selectively enhanced to tones in the attended channel; tones in the central channels in the single-cue conditions, however, produced the least N1 lability and were the least discriminable. The N1 wave was interpreted as a sign of an initial stimulus set or filtering mode of selective attention, whereas a subsequent P3 wave was specifically associated with detections of the target stimuli.     

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)     

Impact of salient vocal qualities on causal attribution for a speaker's behavior.

Two determinants of auditory salience were manipulated—the intensity and sex of a speaker's voice. 98 college students served as listeners. As predicted, Ss attended more to a 75-db than to a 70-db voice on a binaural listening test, and Ss attributed more causality to an actor in a 2-person conversation when his voice was 75 db in intensity than when it was 70 db. Contrary to expectation, Ss listened more to the actor with the male voice. Consistent with this tendency for the male voice to be more salient, Ss attributed more causality to an actor when the voice was male than when it had been electronically converted to a female voice of the same intensity and intonation. Vocal salience also influenced Ss' impressions of the actors, but it had no impact on recall of the actors' verbalizations. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Superior speech comprehension in schizophrenics under monaural versus binaural listening conditions.

20 schizophrenics, 10 nurses, and 10 psychiatric controls (all under age 60) listened to stories and answered the corresponding questions in 3 conditions. All task information was provided either binaurally or exclusively to the left or right ear, and scores were derived from the number of questions answered correctly in each condition. It was hypothesized that schizophrenics would display significant deficits in left ear speech comprehension on the assumption that the patients suffered from poor interhemispheric transfer, which had been observed on manual and visual tasks. Significant left ear deficits were observed in the schizophrenics but not in the controls. An unexpected effect, which may also reflect defective interhemispheric transfer, was that the schizophrenics, but not the controls, displayed significant deficits in binaural relative to right ear speech comprehension. It may be possible to increase the speech comprehension of schizophrenics who show this effect by a simple method that takes advantage of the observed right ear superiority. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reaction time as a function of the cue properties of an auditory display.

An attempt was made to increase the speed of processing verbal directional commands by using the ear stimulated to provide a relevant directional cue. In a choice reaction-time task, Ss pressed the right- or left-hand key in response to: (1) binaural "right" or "left" commands, (2) monaural "right" or "left" commands in the ear corresponding to the content of the command, and (3) monaural pure tones. Responses to the binaural commands were significantly slower than to the other 2 conditions, and responses to the monaural commands were significantly slower than to the monaural tones. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Left-ear superiority in children for processing auditory emotional material.

Investigated hemispheric asymmetries in children for processing auditory material varying in emotional intonation or verbal content. 31 kindergartners, 32 4th graders, and 32 8th graders reported on the emotional content and on the verbal content of dichotically presented sentences. Ss listened to tapes of 4 phrases spoken in tones that were happy, sad, angry, or neutral and to sentences that varied in verbal content only. Ss also completed a handedness questionnaire and a hearing test. All age groups showed a left-ear advantage for reporting on the emotional material and a right-ear advantage for reporting on the verbal material. For the emotional task, the degree of ear asymmetry did not vary significantly as a function of emotional category. Findings indicate the the right hemisphere is specialized for mediating auditory emotional stimuli as early as 5 yrs of age. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)