Significant Left Ear Advantage Research Articles

Left ear advantages in detecting emotional tones using dichotic listening task in an Arabic sample

Advantages associated with the left ear (right brain hemisphere) have been reported in some studies. Of these, some have specifically suggested that the left ear has a more heightened ability to detect emotional tones. Meanwhile others have pointed to factors such as age and gender as potentially leading to manifestations of human laterality. This study investigates which brain hemisphere is more involved in emotional processing of auditory information in Arab participants. We aimed to replicate the previous studies because no single study has been done in the Arabic region previously. Additionally, people in this region prefer to use the right side of their body, e.g., hand, ear, foot, etc., for most daily tasks. To acquire data a dichotic listening task (DLT) was administered to 28 male and 23 female (Edinburgh, UK) university students aged 19 to 38; 13 were left-handed and 38 were right-handed. The results showed a significant left ear advantage in the auditory processing of emotional information. There was a significant negative correlation between ear preference and handedness. Left ear advantage related only to handedness. Thus right-handed participants were more likely than left-handers to have a left ear advantage. The relationship between ear preference and gender was non-significant. The conclusion that might be drawn from this study is that the left ear (right hemisphere) is more involved in emotional processing than the right ear (left hemisphere), especially for right-handed people.

Differences in cognitive control in children and adolescents with combined and inattentive subtypes of ADHD

The aim of the present study was to investigate the ability of children with attention deficit/hyperactivity disorder-combined subtype (ADHD-C) and predominantly inattentive subtype (ADHD-PI) to direct their attention and to exert cognitive control in a forced attention dichotic listening (DL) task. Twenty-nine, medication-naive participants with ADHD-C, 42 with ADHD-PI, and 40 matched healthy controls (HC) between 9 and 16 years were assessed. In the DL task, two different auditory stimuli (syllables) are presented simultaneously, one in each ear. The participants are asked to report the syllable they hear on each trial with no instruction on focus of attention or to explicitly focus attention and to report either the right- or left-ear syllable. The DL procedure is presumed to reflect different cognitive processes: perception (nonforced condition/NF), attention (forced-right condition/FR), and cognitive control (forced-left condition/FL). As expected, all three groups had normal perception and attention. The children and adolescents with ADHD-PI showed a significant right-ear advantage also during the FL condition, while the children and adolescents in the ADHD-C group showed a no-ear advantage and the HC showed a significant left-ear advantage in the FL condition. This suggests that the ADHD subtypes differ in degree of cognitive control impairment. Our results may have implications for further conceptualization, diagnostics, and treatment of ADHD subtypes.

Auditory evoked potentials of adults who do or do not show a significant right ear advantage in dichotic listening

The Halwes Fused Dichotic Words Test was used to divide a sample of university students into a group having a statistically significant right ear advantage (REA) and a group having either a significant left ear advantage or a non-significant ear asymmetry (NREA). Of these participants, 30 (14 REA, 16 NREA) had electrical potentials measured from temporal, central, and frontal sites as series of brief tones were presented monaurally. No behavioural response was required. Group differences were found in the latency but not the amplitude of the averaged event-related responses. The REA group showed faster conduction to the right hemisphere than to the left hemisphere. In both groups the amplitude of left hemisphere responses was greater for right ear stimulation than for left ear stimulation. The results for amplitude indicate that the crossed auditory pathway is a superior conductor of information to the left hemisphere but not to the right hemisphere. Group differences, however, are related only to the speed with which information reaches the right hemisphere.

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 5–8 years 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 9 years 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.

A dichotic listening study of attention control in older adults

The influence of age on attentional control of bottom-up processing was investigated with a dichotic-listening paradigm. The typical right-ear-advantage (REA) without specific attentional instructions was used as a measure of bottom-up processing (non-forced condition). Top-down attentional control was evaluated by instructing subjects to report only the right or left ear stimulus of the dichotic pair (forced-right, forced-left conditions). Both young and old participants showed a REA in the non-forced condition and an increased REA in the forced-right condition. The old group failed, however, to use attention to modulate the REA to the same degree as the younger participants in the forced-left condition. Only the young group showed a significant left ear advantage (LEA). The results are discussed in relation to cognitive decline in normal aging and in early stages of dementia.

The effect of stimulus intensity on the right ear advantage in dichotic listening

The dichotic listening test is non-invasive behavioural technique to study brain lateralization and it has been shown, that its results can be systematically modulated by varying stimulation properties (bottom-up effects) or attentional instructions (top-down effects) of the testing procedure. The goal of the present study was to further investigate the bottom-up modulation, by examining the effect of differences in the right or left ear stimulus intensity on the ear advantage. For this purpose, interaural intensity difference were gradually varied in steps of 3 dB from −21 dB in favour of the left ear to +21 dB in favour of the right ear, also including a no difference baseline condition. Thirty-three right-handed adult participants with normal hearing acuity were tested. The dichotic listening paradigm was based on consonant-vowel stimuli pairs. Only pairs with the same voicing (voice or non-voiced) of the consonant sound were used. The results showed: (a) a significant right ear advantage (REA) for interaural intensity differences from 21 to −3 dB, (b) no ear advantage (NEA) for the −6 dB difference, and (c) a significant left ear advantage (LEA) for differences form −9 to −21 dB. It is concluded that the right ear advantage in dichotic listening to CV syllables withstands an interaural intensity difference of −9 dB before yielding to a significant left ear advantage. This finding could have implications for theories of auditory laterality and hemispheric asymmetry for phonological processing.

Right hemisphere specialization for intensity discrimination of musical and speech sounds

Sound intensity is the primary and most elementary feature of auditory signals. Its discrimination plays a fundamental role in different behaviours related to auditory perception such as sound source localization, motion detection, and recognition of speech sounds. This study was aimed at investigating hemispheric asymmetries for processing intensity of complex tones and consonant-vowel syllables. Forty-four right-handed non-musicians were presented with two dichotic matching-to-sample tests with focused attention: one with complex tones of different intensities (musical test) and the other with consonant-vowel syllables of different intensities (speech test). Intensity differences (60, 70, and 80 dBA) were obtained by altering the gain of a synthesized harmonic tone (260 Hz fundamental frequency) and of a consonant-vowel syllable (/ba/) recorded from a natural voice. Dependent variables were accuracy and reaction time. Results showed a significant clear-cut left ear advantage in both tests for both dependent variables. A monaural control experiment ruled out possible attentional biases. This study provides behavioural evidence of a right hemisphere specialization for the perception of the intensity of musical and speech sounds in healthy subjects.

Laterality in the perception of temporal cues of musical timbre

Laterality in the perception of non-stationary aspects of musical timbre was investigated in 54 right-handed non-musicians. Timbre differences were produced by altering the amplitude envelope of a steady-state complex tone. Two single-choice tests with attention directed to one ear were used—a dichotic test and a monaural test with contralateral white noise. Dependent variables were reaction time and accuracy. Both tests showed a significant left ear advantage for reaction time. For the accuracy variable, a significant left ear advantage was found only in the monaural test. Results are briefly discussed in terms of their compatibility with the generally accepted notion that spectral and temporal integrations of sounds are primarily functions of the right and left hemisphere, respectively.

Hemispheric Involvement in the Perception of Syntactic Prosody Is Dynamically Dependent on Task Demands

The first aim of this study was to determine if there was a significant perceptual asymmetry for syntactic prosody and if it differed from the perceptual asymmetry for emotional prosody. The second aim of this study was to determine if the observed asymmetries were the product of task demands or stimulus features. Experiment 1 consisted of a Syntactic task and an Emotional task. In the Syntactic task, subjects identified Statement and Question prosody in dichotically presented sentences. In the Emotional task, subjects identified Angry and Sad prosody in dichotically presented sentences. There was a significant left ear advantage for the Emotional task and no significant ear advantage for the Syntactic task. In Experiment 2, subjects had to perform an Emotional prosody task with the syntactic Statement and Question prosody stimuli from Experiment 1. There was a significant left ear advantage, indicating that the perceptual asymmetry was determined by task demands and not stimulus features.

Functional Brain Organization in Bipolar Affective Patients during Manic Phase and after Recovery: A Digit Dichotic Listening Study

To study the functional organization of the cerebral hemispheres in patients with bipolar psychosis using a verbal dichotic listening test for pairs of digits 26 patients were tested twice, during the acute expression of manic phase and after recovery. The patient group during the manic phase did not support the expected right-ear advantage of normal subjects on verbal dichotic tests but showed a statistically significant left-ear advantage, which shifted after recovery toward the typical normal asymmetry. Comparing patients during the manic phase and after recovery showed that the left-ear advantage as well as the shift in right-ear advantage after recovery was due to the reduction of left-ear performance. From the over-all neuropsychological findings for these patients mania may be hypothesized to be characterized by overactivation of the right hemisphere. This phaenomenon seems associated with acuteness of the symptoms of the psychotic disorder.

Pathological left-handedness revisited: Dichotic listening in children with left vs right congenital hemiplegia

Thirty-one children with right ( n = 18) and left ( n = 13) congenital hemiplegia were compared for incidence of hand- and foot-preference, eye-dominance, and familial sinistrality. In addition, they were tested with dichotic listening for correct reports of consonant-vowel syllables. The two groups of children were closely matched on IQ and sensory functioning. Children with mental retardation, or epileptic seizures were not included. The results showed that 89% of the left hemisphere impaired (LHI) children were left-handed, all of them preferred the left foot, and 72% were left eye-dominant. In the right hemisphere impaired (RHI) group, everyone (100%) preferred the right hand and foot, and 62% were right eye dominant. The dichotic listening results showed a significant right ear advantage (REA) in the RHI-group, and a significant left ear advantage (LEA) in the LHI-group. The results are discussed in the framework of pathological handedness and shifts in hemisphere control of language in children with early brain injury. It is argued that the homogenous samples, except for the site of lesion, provides an interesting possibility to compare cognitive effects of left and right hemisphere impairement in children.

Event-related potentials and selective attention in major depressive illness

Depressive episodes have been frequently characterized by deficits in information processing efficiency which are particularly evident when required to sustain or focus attention. As cerebral event-related potentials (ERPs) have been shown to reflect various aspects of selective attention and attentional dysfunction, this study attempted to examine ERPs in depressed patients performing a selective auditory attention task. Twenty-nine patients with a diagnosis of major depressive disorder (DSM-III) and 15 normal, non-psychiatric controls served as experimental subjects. Auditory potentials were recorded from the vertex of subjects who listened selectively to a series of tone pips in one ear and ignored concurrent tone pips to the other ear. Tone pips were delivered at short (320–500 ms) interstimulus intervals and subjects were required to detect, within the attended ear, rare ‘target’ tones of a different pitch than the more frequent ‘standard’ tones. In addition to behavioral indices of ‘hits’ and ‘false alarms’, ERP-derived measures included N 1 amplitudes to attended and ignored stimuli, ‘coefficients of attention’ as calculated from N 1 amplitude ratios and the latency onset and amplitude of the ‘negative difference’ (Nd) wave resulting from the subtraction of attended and ignored waveforms. Behavioral measures indicated that depressed patients were as efficient as controls in task performance and in fact they exhibited a significant left ear advantage in the additional task. Although a significant ‘N 1 effect’ was observed with attended tones eliciting larger amplitudes than unattended tones, ERP measures of selective attention did not tend to differentiate the two groups.

Influence of stronger attentional manipulations on the processing of dichotic inputs in right-handers.

Recent studies have shown that a pronounced right-ear advantage can occur within dichotic tasks when persons of a particular sex are directed to focus their attention onto the right ear. To examine the effects of attentional bias on laterality more precisely, we provided subjects a greater number of focused-ear trials. Analysis indicated a very strong right-ear advantage in men and women under the right-focus condition as well as a significant left-ear advantage for both sexes with directed left-focus. These findings suggest that sustained ear-attendance exerts a powerful influence on dichotic performance.

Influence of Stronger Attentional Manipulations on the Processing of Dichotic Inputs in Right-Handers

Recent studies have shown that a pronounced right-ear advantage can occur within dichotic tasks when persons of a particular sex are directed to focus their attention onto the right ear. To examine the effects of attentional bias on laterality more precisely, we provided subjects a greater number of focused-ear trials. Analysis indicated a very strong right-ear advantage in men and women under the right-focus condition as well as a significant left-ear advantage for both sexes with directed left-focus. These findings suggest that sustained ear-attendance exerts a powerful influence on dichotic performance.

Anomalous Dominance in Down Syndrome Young Adults

The ear advantages of groups of Down Syndrome and developmentally retarded (NonDown) young adults, and normal youngsters matched for mental age were compared on dichotic listening performance. The paradigm employed strings of single, double, and triple digits presented to each ear under both free and cued recall conditions. The developmentally retarded and normal groups demonstrated the typical right ear advantage (REA), whereas the Down Syndrome group produced a significant left ear advantage (LEA) in four of the six experimental conditions. In addition, for the cued as compared to free recall conditions, all three groups demonstrated relatively better right ear performance. These results indicate anomalous dominance in Down Syndrome young adults which is consistent across varying memory load and attentional demands. Furthermore, these results are not likely due to a maturational lag phenomenon, but more likely related to genetic, biologic, and neurologic, factors as suggested by Geschwind and Galaburda (1985).

Hemispheric processing of affective and linguistic intonation contours in normal subjects

In a previous study of the comprehension of linguistic prosody in brain-damaged subjects, S. R. Grant and W. O. Dingwall (1984. The role of the right hemisphere in processing linguistic prosody, presentation at the Academy of Aphasia, 1984) demonstrated that the right hemisphere (RH) of nonaphasic patients plays a prominent role in the processing of stress and intonation. The present study examines laterality for affective and linguistic prosody using the dichotic listening paradigm. Both types of prosody elicited a significant left ear advantage. This advantage was more pronounced for affective than for linguistic prosody. These findings strongly support previously documented evidence of RH involvement in the processing of affective prosody ( R. G. Ley & M. P. Bryden, 1982. A dissociation of right and left hemispheric effects for recognizing emotional tone and verbal content, Brain and Cognition, 1, 3–9). They also provide support for the previously mentioned demonstration of RH involvement in the processing of linguistic intonation ( S. Blumstein & W. E. Cooper, 1974. Hemispheric processing of intonation contours, Cortex, 10, 146–158; Grant & Dingwall, 1984).

The influence of gender, handedness and head-turn on auditory asymmetries

Subjects performed dichotic tasks with their heads turned 90° to the left, 90° to the right, and straight ahead. In Experiment 1 the stimuli were digits and the subjects varied in both sex and handedness. Right-handedness males showed a significant right-ear advantage under the head-right and head-straight conditions, while left-handed males and both right- and left-handed females failed to show any consistent ear asymmetries. In Experiment 2 the stimuli were melodies and the subjects were all right-handed. Head-turn had no significant influence on the results, and only the males showed a significant left-ear advantage. Overall, the results confirm previous findings that sex and handedness may influence auditory asymmetries, but fail to reveal systematic effects of head turn.

Failure to replicate the Scott et. al. finding of reversed ear dominance in the native American Navajo

The apparent universality of left hemisphere language specialization in neurologically normal right-handed persons has been questioned by S COTT et al. ( Neuropsychologia 17, 89–92, 1979). They found that Native American Navajos had a significant left ear advantage on the dichotic C-V task, while Anglo Ss had a right ear advantage. We attempted to replicate this finding with essentially the same task, more Ss and four times as many trials. Results showed a very clear right ear advantage in Navajos. While we had previously questioned the Scott et al. conclusion on the basis of visual laterality test findings, present results directly contradict those of Scott et al.

Language lateralization as measured by dichotic VRT and recognition tasks

A dichotic color-naming VRT task and a dichotic digits recognition task were administered. The first required the naming of five colors paired with their backward pronunciation; the second of five nonsimilar digits. Forty-eight right-handed male and female subjects were used, controlling for the factors of sex, handedness, and familial sinistrality. A highly significant left-ear advantage was obtained, suggesting that previous results of dichotic studies may only pertain to a limited class of phenomic stimuli. Results implicate different cerebral processes in the analysis of familiar and novel auditory and phenomic stimuli.

Stimulus dominance in dichotic listening.

Twenty-four listeners received 20 dichotic-listening runs of natural stop-vowel syllables. Listeners marked two responses for each of 30 pairs of syllables per run, which yielded 480 pairs of responses for each of the 30 pairs of syllables. The principal analysis focused on "stimulus dominance" wherein a significantly higher score occurs for one of the competing syllables in a pair regardless of the ear to which that syllable is presented. With 30 pairs of syllables, there were 15 possible instances of stimulus dominance; 11 were observed. The voicing feature was contrasted for 9 of the 15 pairs. Seven of those pairs resulted in significantly higher scores (dominance) for the voiceless stop than for the voiced, one resulted in a higher score for the voiced member of the pair, and for one pair the scores for the two members were essentially the same. Stimulus dominance cannot, however, be characterized sufficiently as a dominance of voiceless over voiced stops; three of the six pairs in which voicing was shared also produced significant stimulus dominance. Stimulus dominance for a given pair of syllables may interact with, and in some cases override, the ear advantage. Of the 30 pairs of syllables, 11 produced a significant right ear advantage (REA), 9 produced a significant left ear advantage (LEA), and for 10 pairs the ear advantage was not significantly different from zero. For a specific pair of syllables, the direction of ear with, and in some cases override, the ear advantage. Of the 30 pairs of syllables, 11 produced a significant right ear advantage (REA), 9 produced a significant left ear advantage (LEA), and for 10 pairs the ear advantage was not significantly different from zero. For a specific pair of syllables, the direction of ear with, and in some cases override, the ear advantage. Of the 30 pairs of syllables, 11 produced a significant right ear advantage (REA), 9 produced a significant left ear advantage (LEA), and for 10 pairs the ear advantage was not significantly different from zero. For a specific pair of syllables, the direction of ear advantage usually corresponded to the ear that received the dominant syllable.