Eye-movement patterns in selective listening tasks of focused attention

Three experiments are described in which eye movements (Ems) were recorded in conjunction with either monaural or dichotic tasks of focused attention. Two main effects were observed in the Ems records: (1) Listening to auditory messages reduced the occurrence of spontaneous Ems. (2) Selective monitoring of one ear in the dichotic task was accompanied by a consistent pattern of directional Ems characterized by big saccades and long changes of eye fixation in the direction of the relevant ear. The pattern of Ems is affected by the following variables: the presentation rate of the auditory information, the frequency of demands to switch orientation between the ears, and the competition of the irrelevant channel in the dichotic task. It is suggested that the eye-movement mechanism is used in selective listening tasks as a general orientation indicator, when the adoption or maintenance of a certain selective set is difficult and demanding of effort. The Ems response is part of a general orientation pattern, although its usual function is in the field of visual perception.     

The verbal transformation effect: auditory illusions as an index of lexical processing and homolog activation.

A technique of inducing auditory illusions was used so that 192 undergraduates heard through headphones either three asynchronous dichotic versions of the same repeating word, at each of three auditory locations (left, center, and right), or only one single repeating word, monaurally or diotically, at each location. Independent illusory changes at each location were reported. Subjects' reports of lexical illusions, but not nonlexical illusions, were fewer at the right ear for three- vs. one-signal listening. These results support the homolog activation hypothesis (Boles, 1990) in which disruption of interhemispheric communication occurs for the hemisphere least capable of processing lexical information. In the current experiment homolog activation led to loss of lexical information when received from auditory positions other than the right, when three signals are presented. Lexical illusions (Verbal Transformations) may be the result of the misapplication of lexical knowledge in an ambiguous situation, listening to a recycling word without stabilizing syntactic or semantic context.     

Exploring temporal dissipation of attention settings in auditory task switching

Using a cued auditory task-switching variant of dichotic listening, we varied the response–cue interval (RCI) to examine temporal dissipation effects. On each trial, participants were presented with two different number words, one spoken by a female speaker and another by a male speaker (dichotic listening), that served as competing targets for a numerical judgment. The gender of the task-relevant speaker was indicated by a visual task cue prior to each trial. Experiment 1A used two different cues for each task (i.e., gender) and showed only small cue repetition benefits (same cue vs. alternate cue) but large auditory switch costs (alternate cue vs. task switch). A replication without immediate cue repetitions (Experiment 1B) showed very similar switch costs, suggesting that immediate cue repetitions play a negligible role for the size of auditory task switch costs. Moreover, switch costs were reduced when the (entirely task-irrelevant) location of the task-relevant speaker changed, relative to when it was unchanged, suggesting an episodic feature-binding component in our dichotic-listening task. Importantly, both experiments showed no effect of RCI on auditory switch costs. Because statistical power for this null effect was reasonably high across experiments (n?=?50), this finding suggests that auditory attention settings do not dissipate quickly over time.     

ERP evidence of early cross-modal links between auditory selective attention and visuo-spatial memory

Previous dual-task research pairing complex visual tasks involving non-spatial cognitive processes during dichotic listening have shown effects on the late component (Ndl) of the negative difference selective attention waveform but no effects on the early (Nde) response suggesting that the Ndl, but not the Nde, is affected by non-spatial processing in a dual-task. Thus to further explore the nature of this dissociation and whether the Nd waveform is affected by spatial processing; fourteen adult participants performed auditory dichotic listening in conjunction with visuo-spatial memory in a cross-modal dual-task paradigm. The results showed that the visuo-spatial memory task decreased both the Nde and Ndl waveforms, and also attenuated P300 and increased its latency. This pattern of results suggests that: (1) the Nde reflects a memory trace that is shared with vision when the information is spatial in nature, and (2) P300 latency appears to be influenced by the discriminability of stimuli underlying the Nde and Ndl memory trace.     

Component problems in dichotic listening

The experiments reported examined monitoring for semantically defined targets whilst concurrently shadowing (Experiment I) or listening silently (Experiment II). The word lists for monitoring were either visual or auditory. Monitoring and shadowing accuracy showed less interference when presentation was bimodal than when it was dichotic. However, monitoring latency and recognition memory for shadowed material did not show this effect. It is argued that these data reveal the existence of a number of different sources of potential difficulty in dichotic listening situations and the nature of these is discussed.     

Right hemisphere comprehension of verbs in patients with complete forebrain commissurotomy: Use of the dichotic method and manual performance

The paradigm of dichotic listening was used to investigate verbal comprehension in the right, so-called “nonverbal,” hemisphere. Verbal commands were presented to the right and left ears in the simultaneous (dichotic) paradigm. There were striking instances, especially when the left hemisphere was occupied with some extraneous task, in which the right hemisphere understood the verbal command and executed the appropriate motor responses. In those instances the left hemisphere gave no overt response. Although the left hemisphere was usually dominant, it can be nevertheless concluded that not only can the right hemisphere understand verbal commands but can also express itself manually by executing actions more complex than object retrieval or pointing. As has been known for some time, the blockage of the ipsilateral pathway seems so complete during dichotic listening in the commissurotomy patient that there is no report of the words in the left ear—only of those presented to the right. At the same time there is normal report when words are presented to the left ear alone. It was found in the present study, however, that this model is too simple and only applies to the verbal response paradigm of dichotic listening. Under circumstances of dichotic presentation where the stimulus in the left ear (ipsilateral pathway) is necessary or important to the left hemisphere for completing a task, words from both pathways are reported. One may conclude that there exists a gating mechanism in each hemisphere that controls the monitoring of each auditory pathway and the degree of ipsilateral suppression.     

Stimulus intensity, attentional instructions, and the ear advantage during dichotic listening

The present experiment was designed to investigate the effects of the following two variables on the identification of dichotically presented CV syllables: (1) the relative difference in intensity levels of the stimuli presented to the two ears and (2) the instructions to attend to both ears or to focus attention on one ear. As expected for a verbal task, more CV's were identified from the right ear than from the left ear. Furthermore, identification of stimuli presented to one ear improved when (1) those stimuli were relatively higher in volume than the stimuli presented to the other ear and (2) when subjects were instructed to focus attention on only that ear rather than distribute attention across both ears. Of particular importance is the finding that the effects of relative stimulus intensity are the same under conditions of focused attention as under conditions of divided attention. This finding is inconsistent with an attention explantation of the relative intensity effects. Instead, the results are consistent with a model of dichotic listening in which ear of stimulus presentation and relative stimulus intensity influence a perceptual stage of information processing and attentional instructions influence a subsequent response selection stage.     

The influences of listening and speaking on pedestrians' assessments of approaching vehicles

Research suggests a relationship between auditory distraction (such as environmental noises or a vocal cell phone conversation) and a decreased ability to detect and localize approaching vehicles. What is unclear is whether auditory vehicle perception is impacted more by distractions reliant on listening or distractions reliant on speaking (analogous to the two components of a vocal cell phone conversation). In two experiments, adult participants listened for approaching vehicle noises and while performing listening- and speaking-based secondary tasks. Participants were tasked with identifying when they first detect an approaching vehicle and when they no longer felt safe to cross in front of the approaching vehicle. For both experiments, the speaking task resulted in significantly later detection of approaching vehicles and riskier crossing thresholds than in the no-distraction and listening conditions. The listening secondary task significantly differed from the control condition in experiment 1, but not experiment 2. Overall, our results suggest auditory distractions, particularly those reliant on speaking, negatively impact pedestrian safety in situations where visual information is minimal. Results may provide guidance for future research and policy about the safety impacts of secondary tasks.     

Dichotic listening with forced attention in patients with temporal lobe epilepsy: significance of left hemisphere cognitive dysfunction

Fifty right-handed patients with focal temporal lobe epilepsy were administered a dichotic listening test with consonant-vowel syllables under non-forced, forced right and forced left attention conditions, and a neuropsychological test battery. Dichotic listening performance was compared in subgroups with and without left hemisphere cognitive dysfunction, measured by the test battery, and in subgroups with left and right temporal epileptic focus. Left hemisphere cognitive dysfunction led to more correct responses to left ear stimuli in all three attention conditions, and fewer correct responses to right ear stimuli in the non-forced attention condition. This was probably caused by basic left hemisphere perceptual dysfunction. Dichotic listening was less affected by a left-sided epileptic focus than by left hemisphere cognitive dysfunction. General cognitive functioning influenced dichotic listening performance stronger in forced than in non-forced attention conditions. Larger cerebral networks were probably involved in the forced attention conditions due to the emphasis on conscious effort.     

Auditory neglect after right frontal lobe and right pulvinar thalamic lesions

Auditory unilateral neglect or extinction to simultaneous stimulation is reported in a right-handed male with a lesion in the right frontal lobe and in the right thalamic pulvinar area. The patient was submitted to stereotactic thalamotomy for a post-traumatic intentional ataxia in the left extremities. He was subjected to repeated tests with dichotic listening to consonant-vowel syllables under three different attentional instructions. He was also tested monaurally with the same stimulus materials as used in the dichotic test. The results showed almost complete extinction of the left ear input during dichotic presentations, despite normal hearing when tested with audiometer screening. The left ear extinction effect was independent of instructions to attend to the left or right ear input. However, during monaural presentation, correct left ear reports increased to about 85%. The results are interpreted as showing an auditory attentional neglect caused by the right frontal and pulvinar lesions.     

Perceptual difficulty and the right ear advantage for vowels

The results of a series of four dichotic listening experiments confirm that under appropriate conditions vowels show a right ear advantage (REA) comparable to that of consonants. The conditions all cause perceptual difficulty, adversely affecting the accurate registration of both inputs in the auditory system. The addition of noise, shortening of the vowel stimuli, and the use of a more confusable set of vowels, each had the effect of increasing REA. Results are compatible with an explanation of ear advantage in terms of competition at the auditory rather than the phonetic level, in which short-term precategorical acoustic storage (PAS) may play a critical role.     

Effects of dichotic listening on gait domains of healthy older adults during dual-tasking: An exploratory observational study

BackgroundIdentification of the cognitive mechanisms behind gait changes in aging is a prime endeavor in gerontology and geriatrics. For this reason, we have implemented a new dual-task paradigm where an auditory attentional task is performed during over-ground walking. Dichotic listening assesses spontaneous attention and voluntary attention directed to right and left-ear. The uniqueness of dichotic listening relies on its requirements that vary in difficulty and recruitment of resources from whole brain to one brain hemisphere. When used in dual-tasking, asymmetric effects on certain gait parameters have been reported.ObjectivesThe present study aims to acquire a more global understanding on how dichotic listening affects gait domains. Specifically, we aimed to understand how spontaneous vs lateralized auditory attention altered the Principal Component Analysis (PCA) structure of gait in healthy older adults.MethodsSeventy-eight healthy older adults (mean age: 71.1 years; 44 women and 34 men) underwent the Bergen dichotic listening test while walking. As this study only focuses on the effects of the cognitive task on gait, only dual-task costs for gait were calculated and entered into the PCA analyses. We explored the PCA structure for the effects on bilateral gait parameters (i.e., both limbs together) as well as on lateralized gait parameters (i.e, separate parameters by limb). We first established gait domains during single-task walking. Then, dual-task cost scores for gait were entered in a series of PCAs.ResultsResults from the PCAs for bilateral gait parameters showed limited alterations on gait structure. In contrast, PCAs for lateralized data demonstrated modifications of the gait structure during dichotic listening. The PCAs corresponding for all dichotic listening conditions showed different factor solutions ranging between 4 and 6 factors that explained between 73.8% to 80% of the total variance. As a whole, all conditions had an impact on “pace”, “pace variability” and “base of support variability” domains. In the spontaneous attention condition, a six-factor solution explaining 78.3% of the variance showed asymmetrical disruptions on the PCA structure. When attention was focused to right-ear, a five-factor solution explaining 89% of the variance and similar to baseline was found. When attention was directed to left-ear, a four-factor solution explaining 73.8% of the variance was found with symmetrical impact on all factors.ConclusionsThese findings demonstrate for the first time that specific facets of attentional control affects gait domains both symmetrically and asymmetrically in healthy older adults.     

Feature mismatch effects in auditory negative priming: interference as dependent on salient aspects of prior episodes

A handful of studies have revealed that withholding a response to a sound causes impaired responding to that sound when subsequently presented (Buchner & Steffens, 2001; Mondor, Leboe, & Leboe, 2005). In the present study, we investigated whether a switch in the location of a repeated sound might represent an additional source of this auditory negative priming effect. In all three of our experiments, participants performed a series of trials in which they withheld a response to a dichotic pair of prime sounds presented to each ear. A dichotic pair of probe sounds was then presented to each ear, and the participants were required to categorize one of them. Across these experiments, the participants were slower to categorize only repeated sounds that were presented in opposite locations.     

Effects of expectancy and order of report on auditory asymmetries

This study examined the relation between selective attention, perception, and memory factors in the generation of auditory asymmetries. Sixty subjects were randomly assigned to one of three dichotic listening groups. One group was presented with paired linguistic stimuli, a second group with dichotic nonverbal material, while a third group heard randomly inteterspersed verbal and nonverbal pairs. Order of ear report was controlled in all three groups. Significant right ear advantages on first and second reports were found in the verbal group, and a similar pattern of left ear advantages was found in the nonverbal group. This ear by material dissociation was only found on second ear reports in the group which heard the randomly interspersed pairs. No first report ear advantages were evident in the latter group. These results are discussed in terms of the independence of perceptual and memory mechanisms in the production of auditory asymmetries.     

Attentional Effects in Dichotic Listening

This study addresses attentional effects in dichotic listening (DL) to consonant-vowel syllables. Previous research has shown that ear advantages in DL are modulated by biased attention to either the left or the right ear. Attentional effects in DL can be the result of two processes: facilitation of reports from the attended ear, or suppression of intrusions from the nonattended ear. Sixty-two students were tested with DL under three different task instructions: nonforced (divided) attention, attention forced to the right ear, and attention forced to the left ear. The main finding was inhibition of intrusions from the nonattended ear, combined with the facilitation of the correct reports from the attended ear during the two forced-attention conditions, compared with the nonforced condition. The results are discussed in relation to right hemisphere processing of dichotic input, and that attention may activate subcortically biased asymmetries which suppress input from the nonattended channel.     

Feature mismatch effects in auditory negative

A handful of studies have revealed that withholding a response to a sound causes impaired responding to that sound when subsequently presented (Buchner & Steffens, 2001; Mondor, Leboe, & Leboe, 2005). In the present study, we investigated whether a switch in the location of a repeated sound might represent an additional source of this auditory negative priming effect. In all three of our experiments, participants performed a series of trials in which they withheld a response to a dichotic pair of prime sounds presented to each ear. A dichotic pair ofprobe sounds was then presented to each ear, and the participants were required to categorize one of them. Across these experiments, the participants were slower to categorize only repeated sounds that were presented in opposite locations.     

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.     

On the relation between auditory spatial attention and auditory perceptual asymmetries.

Laterality investigators have typically interpreted any perceptual asymmetry as a direct expression of the functional organization of the brain. However, many other confounding factors, including the asymmetric distribution of attention, may also contribute to either the magnitude or the direction of any of these advantages. In two experiments, attention was manipulated in a dichotic listening paradigm by presenting a preexposural tone cue to the ear from which the subject was required to report. The time available to orient attention was manipulated by varying the time period between the onset of the cue and the onset of the trial (stimulus onset asynchrony, or SOA). Results indicated that a right ear advantage for the identification of verbal material obtained at a 150-msec SOA was almost completely eliminated at an SOA of 450 msec. In addition, the direction of the ear advantage for emotion identification was found to depend on task difficulty. A left ear advantage, apparent when task difficulty was minimal, was reversed to a right ear advantage when difficulty was increased. These data are taken as evidence that, when subjects are faced with a difficult dichotic task, there is a general tendency for right-handed subjects to bias their attention toward the right ear. Such a tendency is shown not only to have likely seriously compromised the results of past investigations of functional perceptual asymmetries but also to be inconsistent with previously proposed theories of dichotic listening performance.     

On the relation between auditory spatial attention and auditory perceptual asymmetries

Laterality investigators have typically interpreted any perceptual asymmetry as a direct expression of the functional organization of the brain. However, many other confounding factors, including the asymmetric distribution of attention, may also contribute to either the magnitude or the direction of any of these advantages. In two experiments, attention was manipulated in a dichotic listening paradigm by presenting a preexposural tone cue to the ear from which the subject was required to report. The time available to orient attention was manipulated by varying the time period between the onset of the cue and the onset of the trial (stimulus onset asynchrony, or SOA).Results indicated that a right ear advantage for the identification of verbal material obtained at a 150-msec SOA was almost completely eliminated at an SOA of 450 msec. In addition, the direction of the ear advantage for emotion identification was found to depend on task difficulty. A left ear advantage, apparent when task difficulty was minimal, was reversed to a right ear advantage when difficulty was increased. These data are taken as evidence that, when subjects are faced with a difficult dichotic task, there is a general tendency for right-handed subjects to bias their attention toward the right ear. Such a tendency is shown not only to have likely seriously compromised the results of past investigations of functional perceptual asymmetries but also to be inconsistent with previously proposed theories of dichotic listening performance.     

On the division of attention: A disproof of the single channel hypothesis

In dichotic listening, subjects are apparently unable to attend simultaneously to two concurrent, auditory speech messages. However, in two experiments reported here, it is shown that people can attend to and repeat back continuous speech at the same time as taking in complex, unrelated visual scenes, or even while sight-reading piano music. In both cases performance with divided attention was very good, and in the case of sight-reading was as good as with undivided attention. There was little or no effect of the dual task on the accuracy of speech shadowing. These results are incompatible with the hypothesis that human attention is limited by the capacity of a general-purpose central processor in the nervous system. An alternative, “multi-channel”, hypothesis is outlined.