Accuracy of recognition for speech presented to the right and left ears

Earlier reports by other authors had shown that recall of dichotically presented speech was better for words arriving at the right ear, while recognition of passages of music was better for music presented to the left ear. It seemed desirable to test recognition for speech, in order to show that the difference between materials rather than the difference in testing techniques was responsible for this disparity between ears.

Accordingly 18 men were presented with dichotic lists of digits, and then tested for recognition of the digits. There was no indication of an advantage for the left ear, but rather of the advantage for the right already established for recall of speech materials.     

Emergence of unreported stimuli into imagery as a function of laterality of presentation: a replication and extension of research by Henley & Dixon (1974).

In Expt. 1, the research by Henley & Dixon (1974) was replicated. Two experimental groups (n=8 each) received subliminal words to the right ear and 8 min of music to the left ear or vice versa. Each group had its own control (n=8 each) with only music to one ear. Categorization and ranking of imagery reported, as well as performance on a checklist containing critical, associated, and non-related words, showed that emergence was greater with words to the right ear than with no words. There was no difference between experimental and control groups with words to the left ear. In Expt. 2, the music was eliminated, and subjects received subliminal words to the right ear (n=8) or no words. A significant difference between groups was found when the reported imagery was ranked as to emergence, and on the checklist, but not when the reports were categorized by judges.     

Music during learning of a tactual-spatial task affects later response generalization

Equal numbers of men and women learned a finger maze, with half of the subjects initially using their right hands and the other half using their left hands. To reach criterion, subjects receiving music in the ear ipsilateral to the hand used required more trials than did those receiving no music. Furthermore, when the right hand ran the maze, music played to the ipsilateral ear also delayed learning, compared with music played contralaterally. Binaural music delayed learning when the left hand was used but not when the right hand was used. Possible causes of these effects are suggested. When subjects switched hands and relearned the maze, the number of trials to criterion depended on the group subjects were in during initial learning and not on the group they were in during the hand reversal (response generalization) trials. Although the music condition used determined the effect of music on initial learning and on response generalization, some evidence is presented that indicates that the two effects are not entirely interdependent and that they may even involve different mechanisms.     

Selective attention and cerebral dominance in perceiving and responding to speech messages

The effect of attention on cerebral dominance and the asymmetry between left and right ears was investigated using a selective listening task. Right handed subjects were presented with simultaneous dichotic speech messages; they shadowed one message in either the right or left ear and at the same time tapped with either the right or the left hand when they heard a specified target word in either message. The ear asymmetry was shown only when subjects' attention was focused on some other aspect of the task: they tapped to more targets in the right ear, but only when these came in the non-shadowed message; they made more shadowing errors with the left ear message, but chiefly for non-target words. The verbal response of shadowing showed the right ear dominance more clearly than the manual response of tapping. Tapping with the left hand interfered more with shadowing than tapping with the right hand, but there was little correlation between the degree of hand and of ear asymmetry over individual subjects. The results support the idea that the right ear dominance is primarily a quantitative difference in the distribution of attention to left and right ear inputs reaching the left hemisphere speech areas. This affects both the efficiency of speech perception and the degree of response competition between simultaneous verbal and manual responses.     

Speech and music draw attention to the right ear in stereophonic listening

This study investigated whether right-handed subjects would prefer the right ear for normal speech and the left ear for musical stimuli. Right-handed college students (9 women and 2 men) were presented two stereophonic tape recordings, one of normal speech, the other of nonlyrical, orchestral music. Subjects used an attenuator to match the intensity of signals in the left and right earphones. The subjects consistently favored the right side in both conditions. These findings are inconsistent with those of other researchers, such as Segalowitz and Plantery. However, the findings support the 1980 research of Porac, Coren, and Duncan, offering perceptual evidence of a general right-ear bias in right-handed subjects.     

Ear asymmetries on a selective attentional task

To ascertain whether there are ear-hemisphere asymmetries of selective attention, signal stimuli (tonal sequences) were presented monaurally with and without complex maskers (music and speech). The right ear-left hemisphere was more disrupted by language maskers; the left ear-right hemisphere was more disrupted by music maskers. These results suggest that there are hemispheric asymmetries of selective attention and that the ear hemisphere that usually processes a class of stimuli has greater difficulty filtering out those stimuli than does the nonspecialized hemisphere.     

Dichotic recognition of musical canons: Effects of leading ear and time lag between ears

A musical canon consists of two melodic lines with the second part copying the first exactly after some time delay. Right-handed adults listened to canons presented dichotically at time delays between the ears of 2, 4, and 8 sec. Presentation rate varied from 1.0 to 4.4 notes/sec in one part. Different groups of subjects heard the canons with the left or the right ear leading. The subject’s task was to tell whether a given stimulus was a canon or not. Control stimuli were noncanons by the same composer. Musically experienced subjects performed better at the task than inexperienced subjects. Short time lags were easier than long, and the effect of lag was more pronounced with the right ear leading. In the light of previous evidence of functional ear asymmetry in music perception, these results suggest that whenever possible subjects use a strategy of selecting out small chunks of the lead-ear melody for short-term memory storage and later comparison with the trailing melody. The auditory system processing information from the right ear is especially good at focusing on small chunks. But this strategy is particularly vulnerable to time lag; hence the interaction of lead ear and time lag.     

Perception of clicks in music

Subjects were asked to judge the position of a click that occurred during a short piece of music. Clicks were, on average, judged to be later than their actual position. The click and the music were presented through headphones to different ears, and the clicks were judged to be significantly later if they arrived at the right ear rather than at the left. There was also a significant tendency for clicks to be attracted to phrase boundaries in the music. These last two results are similar to those from experiments with a click during speech, but the late judgments of a click in music contrast with the early judgments of a click in speech.     

Right-ear advantage and delayed recall

Two studies were performed using monaural presentation of verbal material to test for a right-ear advantage (REA) in recall. It was hypothesized that a delayed recall task and examination of the serial position curve would be a more sensitive test for ear asymmetries than those used in previous studies. In Experiment 1, 30 right-handed male subjects were given lists of words to recall, presented to either the left or right ear, with language chatter, baroque music, or no stimulus concurrently presented to the opposite ear. Both immediate and delayed recall were assessed. The results indicated that the strongest REAs appeared in delayed recall. Moreover, the REAs occurred regardless of the stimulus conditions co-occurring in the other ear. Experiment 2 was done to test whether the REAs in the delayed recall were due to rehearsal biases. Twenty-four right-handed male subjects recalled lists of words with standard instructions and instructions to recall in the reverse order of input (limiting rehearsal). The results indicated that the backward instructions limited and controlled rehearsal and, hence, input to long-term storage; the REAs occurred in delayed recall under all instructional conditions.     

The investigation of ear asymmetry by simple and disjunctive reaction-time tasks

In a disjunctive reaction-time task in which Ss responded to clicks presented to one ear while white noise was presented to the other, RT was significantly faster to stimuli presented to the left ear than to the right ear. In a simple reaction-time task, using the same stimuli. there was no difference in R T to stimuli presented to right or left ear. The results were discussed in relation to functional asymmetry of the cerebral hemispheres. and were taken to support a perceptual interpretation of the ear asymmetry effect.     

Auditory lateralization: An effect of rhythm

Recall of monaurally presented semantically anomalous sentences, which had either neutral or rhythmic timing, was tested at the right ear, at the left ear, and on transfer from one ear to the other. The component words, being computer stored digitized waveforms, had identical acoustic structure in the two conditions. In the rhythmic condition there was not only an overall advantage in the second half of the experiment but also an asymmetric transfer effect such that this advantage did not appear when the left ear was tested after the right. It is proposed that functional lateralization be viewed as an adaptive, dynamic, organizational factor.     

Effects of eye movements on the recognition and localization of dichotic stimuli

Three experiments examined the effect of gaze shifts on overall performance and ear differences in dichotic listening. In the first two experiments, lights were switched on and off so as to induce rightward, leftward, or upward gaze during dichotic stimulation. The dichotic material consisted of musical passages in Experiment 1 and two kinds of verbal material in Experiment 2. Vertical eye movements enhanced the accuracy of identification of music but not verbal material. The lateral direction of eye movements affected subjects' ability to localize targets in Experiment 1: localization was more accurate in the direction toward which subjects were looking. In the third experiment it was found that optokinetic nystagmus (OKN) influenced the asymmetry of performance on a dichotic consonant-vowel (CV) test. The right-ear advantage was greatest when the OKN drum rotated from left to right and least when it rotated from right to left. The effect was due to corresponding variation in left-ear scores. Possible mechanisms through which shifts of gaze affect auditory identification and localization are proposed.     

The Phonetic Integration of Speech and Non-speech Sounds: Effects of Perceived Location

The third-formant (F3) transition of a three-formant /da/ or /ga/ syllable was extracted and replaced by sine-wave transitions that followed the F3 centre frequency. The syllable without the F3 transition (base) was always presented at the left ear, and a /da/ (falling) or /ga/ (rising) sine-wave transition could be presented at either the left, the right, or both ears. The listeners perceived the base as a syllable, and the sine-wave transition as a non-speech whistle, which was lateralized near the left ear, the right ear, or the middle of the head, respectively. In Experiment 1, the sine-wave transition strongly influenced the identity of the syllable only when it was lateralized at the same ear as the base (left ear). Phonetic integration between the base and the transitions became weak, but was not completely eliminated, when the latter was perceived near the middle of the head or at the opposite ear as the base (right ear). The second experiment replicated these findings by using duplex stimuli in which the level of the sine-wave transitions was such that the subjects could not reliably tell whether a /da/ or a /ga/ transition was present at the same ear as the base. This condition was introduced in order to control for the possibility that the subjects could have identified the syallables by associating a rising or falling transition presented at the left ear with a /da/ or /ga/ percept. Alternative suggestions about the relation between speech and non-speech perceptual processes are discussed on the basis of these results.     

Protective inhibition: A central factor in auditory fatigue

Summary A signal detection experiment was performed to investigate the sensitivity shift after stimulation with discontinuous octave-band noise of 95 dB (A). The influence of psychological factors on the sensitivity shift in the stimulated and the unstimulated ear was investigated in a two-factorial experimental design. In four independent groups of 12 Ss each, the psychological meaning of the noise and the side of sensitivity measurement were varied. Half of the Ss listened passively to the noise stimuli (control groups), the other half was made to believe that the noise signaled errors in a tracking task (experimental groups). After exposure of noise stimuli to the right ear the sensitivity of either the right or the left ear was determined. After exposure to noise the sensitivity of the stimulated ear was shown to be significantly more reduced in the experimental than in the control group. Thus, depending on the meaning of the noise physically identical stimuli produce sensitivity shifts of different amounts. After stimulation of the right ear with noise the sensitivity of the left ear remained completely unaffected. The sensitivity shift of the right ear did not persist as long as a threshold shift would have done. The hypothesis is that intensive auditory stimuli will produce negative feedback which protects — within certain limits — the stimulated ear from the fatiguing after-effects of overstimulation. The effectiveness of this protective inhibition depends on psychological factors.We are grateful to S. Jörg-Wagner for his competent handling of the experiment.     

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.

     

Improving left spatial neglect through music scale playing

The study assessed whether the auditory reference provided by a music scale could improve spatial exploration of a standard musical instrument keyboard in right‐brain‐damaged patients with left spatial neglect. As performing music scales involves the production of predictable successive pitches, the expectation of the subsequent note may facilitate patients to explore a larger extension of space in the left affected side, during the production of music scales from right to left. Eleven right‐brain‐damaged stroke patients with left spatial neglect, 12 patients without neglect, and 12 age‐matched healthy participants played descending scales on a music keyboard. In a counterbalanced design, the participants' exploratory performance was assessed while producing scales in three feedback conditions: With congruent sound, no‐sound, or random sound feedback provided by the keyboard. The number of keys played and the timing of key press were recorded. Spatial exploration by patients with left neglect was superior with congruent sound feedback, compared to both Silence and Random sound conditions. Both the congruent and incongruent sound conditions were associated with a greater deceleration in all groups. The frame provided by the music scale improves exploration of the left side of space, contralateral to the right hemisphere, damaged in patients with left neglect. Performing a scale with congruent sounds may trigger at some extent preserved auditory and spatial multisensory representations of successive sounds, thus influencing the time course of space scanning, and ultimately resulting in a more extensive spatial exploration. These findings offer new perspectives also for the rehabilitation of the disorder.     

Effects of hemispheric asymmetry on electrodermal conditioning in a dichotic listening paradigm

It was predicted that when an auditive verbal conditional stimulus (CS+), previously associated with an aversive unconditional stimulus (UCS), is presented to theright ear (initial left hemisphere input), in a dichotic listening task, with the CS-simultaneously presented in the left ear, the result would be greater resistance to extinction than when the same CS+ is presented to the left ear (initial right hemisphere input). In the same vein, it was predicted that, when a tonal CS+ is presented to theleft ear, greater resistance to extinction would occur as compared with when it is presented to the right ear. During a dichotic test phase, each group was split into two subgroups, and the CS+ and CS—repeatedly were presented simultaneously to each ear. Half of the subjects in each subgroup had the CS+ presented to the left ear. The other half had the CS+ presented to the right ear. Skin conductance responses were recorded from both hands. Results showed significantly larger responding in all groups to the CS+/UCS compound during the acquisition phase. However, during the dichotic extinction phase, the verbal CS+ right-ear subgroup showed significantly larger resistance to extinction as compared with the verbal CS+ left-ear subgroup. No differences were found between the two tonal subgroups.     

EEG alpha desynchronization in musicians and nonmusicians in response to changes in melody, tempo, and key in classical music

Two experiments were performed to examine musicians' and nonmusicians' electroencephalographic (EEG) responses to changes in major dimensions (tempo, melody, and key) of classical music. In Exp. 1, 12 nonmusicians' and 12 musicians' EEGs during melody and tempo changes in classical music showed more alpha desynchronization in the left hemisphere (F3) for changes in tempo than in the right. For melody, the nonmusicians were more right-sided (F4) than left in activation, and musicians showed no left-right differences. In Exp. 2, 18 musicians' and 18 nonmusicians' EEG after a key change in classical music showed that distant key changes elicited more right frontal (F4) alpha desynchronization than left. Musicians showed more reaction to key changes than nonmusicians and instructions to attend to key changes had no significant effect. Classical music, given its well-defined structure, offers a unique set of stimuli to study the brain. Results support the concept of hierarchical modularity in music processing that may be automatic.     

Hemispheric asymmetry and human associative learning: Interactions with attention

In a previous study (Hugdahl & Brobeck, 1986) it was shown that Pavlovian conditioning to an auditory verbal conditioned stimulus (CS) initially presented only to the left cerebral hemisphere was stronger than when the same CS was presented to the right hemisphere. This was followed up in the present study by controlling for the possibility that the effect was caused by laterally biased attention. The study was performed using the “dichotic extinction paradigm,” which consists of three different phases. During the habituation phase, the CS+ and CS- were presented binaurally and separated in time. During the acquisition phase, the CS+ was followed by a white-noise unconditioned stimulus (UCS). During the dichotic extinction phase, the CS+ and CS- were presented dichotically, i.e., simultaneous presentations on each trial. Half of the subjects had the CS+ in the right ear, and half had the CS+ in the left ear. Each group was further divided into two subgroups, with one subgroup instructed to attend only to the right ear input, and the other subgroup to attend only to the left ear input. During acquisition, larger electrodermal responses were obtained to the CS+ than to the CS-. During dichotic extinction, the CS+ right ear group showed superior resistance to extinction compared to the CS+ left ear group, with no effect of the manipulation of attention. The effect was, however, attenuated when levels of acquisition was used as covariates in an analysis of covariance. There were overall larger responses from the left hand recording.     

Auditory lateralization for speech in language-impaired children.

The ability of five language-impaired (LI) children and five matched controls, aged 7-10 years, to discriminate natural pairs of consonant-vowel syllables contrasted on place of articulation and voicing, presented to the right or left ear with white noise in the contralateral ear, was investigated. The general pattern of errors indicated that LI children had more difficulty than controls in discriminating place of articulation contrasts only when they were presented to the left ear, as well as a difficulty in discriminating voice contrasts selective to the right ear. The results are discussed in terms of acoustic integration and suggest that bihemispheric dysfunction is a basis for specific language impairment.