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.     

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.     

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.     

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.     

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.     

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.     

Selective attention fails to alter the dichotic listening lag effect: evidence that the lag effect is preattentional

Berlin et al. (1973) reported that either stimulus from a dichotic pair of consonant-vowel syllables is processed preferentially when its presentation is delayed by 30-60 ms. In the first of three experiments with 60 normal right-handed adults, we replicated the Berlin et al. "lag effect," but only for asynchronies between 60 and 90 ms. In Experiment 2 subjects focused attention selectively on one ear. The results indicated that focused attention and stimulus asynchrony have additive effects: Performance improved at the attended ear irrespective of stimulus asynchrony, but the lag effect remained unchanged relative to the divided-attention condition. Experiment 3 entailed a signal detection task that allowed separate analysis of detection and localization accuracy. As in previous studies, selective attention to one ear increased the accuracy of localization but not detection at the attended ear. Both dependent measures indicated a lag effect that remained invariant as attention was manipulated. These findings imply that the lag effect is attributable to a preattentional stage of auditory processing.     

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.     

Electrodermal responses to attended and nonattended significant stimuli during dichotic listening

Some investigators have found that words previously associated with shock elicit electrodermal responses (EDRs) when presented in the nonattended channel of a dichotic listening task. The present experiment tested for this phenomenon while closely monitoring for shifts in attention to the nonattended channel. College student volunteers verbally shadowed a series of unrelated words presented to the attended channel while words made significant by previous association with shock (and semantically related words) were occasionally presented to the nonattended channel. Three principal findings were obtained. Fist, when EDRs were averaged across all trials and across all subjects, it was found that EDRs were elicited by the significant words presented in the nonattended channel. Second, for the subgroup of subjects that had the significant words presented to the right ear (activating the left cerebral hemisphere), it was found that EDRs were elicited by the significant words presented to the left ear (activating the right cerebral hemisphere), it was found that EDRs were elicited by the significant word seven on trials on which there were no apparent shifts in attention. The results of this study indicate the importance of closely controlling and monitoring for shifts in attention and suggest the potential importance of cerebral laterality in mediating EDRs to stimuli presented in a nonatttended channel.     

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.     

The influence of visual information on auditory lateralization

Sætrevik, B. (2010). The influence of visual information on auditory lateralization. Scandinavian Journal of Psychology. The classic McGurk study showed that presentation of one syllable in the visual modality simultaneous with a different syllable in the auditory modality creates the perception of a third, not presented syllable. The current study presented dichotic syllable pairs (one in each ear) simultaneously with video clips of a mouth pronouncing the syllables from one of the ears, or pronouncing a syllable that was not part of the dichotic pair. When asked to report the auditory stimuli, responses were shifted towards selecting the auditory stimulus from the side that matched the visual stimulus.     

Individual differences in working memory capacity and divided attention in dichotic listening

The controlled attention theory of working memory suggests that individuals with greater working memory capacity (WMC) are better able to control or focus their attention than individuals with lesser WMC. This relationship has been observed in a number of selective attention paradigms including a dichotic listening task (Conway, Cowan, & Bunting, 2001) in which participants were required to shadow words presented to one ear and ignore words presented to the other ear. Conway et al. found that when the participant’s name was presented to the ignored ear, 65% of participants with low WMC reported hearing their name, compared to only 20% of participants with high WMC, suggesting greater selective attention on the part of high WMC participants. In the present study, individual differences in divided attention were examined in a dichotic listening task, in which participants shadowed one message and listened for their own name in the other message. Here we find that 66.7% of high WMC and 34.5% of low WMC participants detected their name. These results suggest that as WMC capacity increases, so does the ability to control the focus of attention, with high WMC participants being able to flexibly “zoom in” or “zoom out” depending on task demands.     

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.     

Impaired auditory attention skills following middle-ear infections.

The present study investigated auditory attention skills in a sample of children with non-chronic otitis media with effusion (OME). Twenty children with repeated episodes of OME but not found in the need for myringotomy and insertion of ventilating tubes were compared to 20 control children with no known episodes of OME based on parental reports and medical records. Mean age during assessment was 9 years, and none of the children showed signs of impaired language functions and with normal general cognitive abilities. They were assessed with dichotic listening CV-syllables (DLCV-108) free recall and directed attention tasks. The control children showed the expected right ear advantage during free recall and the directed right condition, and demonstrated a shift toward a left ear advantage during the directed left. The children with a history of OME showed a predominant right ear advantage across all three tasks. Although some change in ear accuracy occurred across tasks, impaired auditory attention skills were found following a history of middle ear infections. These results replicate those reported earlier from a sample of children with persistent otitis media with effusion, and suggest that treatment with ventilating tubes does not appear to make any difference in the development of auditory attention skills, whereas occurrence of OME must be considered when testing auditory attentional skills as a part of a neuropsychological assessment.     

Focused and Nonfocused Attention in Verbal and Emotional Dichotic Listening: An FMRI Study

Functional magnetic resonance imaging (fMRI) was used to identify cortical regions which are involved in two dichotic listening tasks. During one task the subjects were required to allocate attention to both ears and to detect a specific target word (phonetic task), while during a second task the subjects were required to detect a specific emotional tone (emotional task). During three attentional conditions of each task, the subjects were required to focus attention to the right (FR) or left ear (FL), while during a third condition subjects were required to allocate attention to both ears simultaneously. In 11 right-handed male subjects, these dichotic listening tasks evoked strong activations in a temporofrontal network involving auditory cortices located in the temporal lobe and prefrontal brain regions. Hemodynamic responses were measured in the following regions of interest: Heschl's gyrus (HG), the planum polare (PP), the planum temporale (PT), the anterior superior temporal sulcus (aSTS), the posterior superior temporal sulcus (pSTS), and the inferior frontal gyrus region (IFG) of both hemispheres. The following findings were obtained: (1) the degree of activation in HG and PP depends on the direction of attention. In particular it was found that selectively attending to right-ear input led to increased activity specifically in the left HG and PP and attention to left ear input increased right-sided activity in these structures; (2) hemodynamic responses in the PT, aSTS, pSTS, and IFG were not modulated by the different focused-attention conditions; (3) hemodynamic responses in HG and PP in the nonforced conditions were the sum activation of the forced conditions; (4) there was no general difference between the phonetic and emotion tasks in terms of hemodynamic responses; (5) hemodynamic responses in the PT and pSTS were strongly left-lateralized, reflecting the specialization of these brain regions for language processing. These findings are discussed in the context of current theories of hemispheric specialization.     

Information processing and speech lateralization in learning-disabled children

The relationship between information processing and speech lateralization was investigated in learning-disabled children. The Kaufman Assessment Battery for Children (K-ABC) assessed simultaneous and successive processing while a dichotic listening paradigm with free recall and directed attention conditions assessed speech lateralization. A three-factor ANOVA design conducted on the dichotic data revealed that normal children demonstrated stronger right ear advantage (REA); whereas learning-disabled showed weaker right ear advantage. Further, lambda analyses conducted on individual subjects revealed that the learning-disabled did not demonstrate the REA, were not biased attenders, and did not get more right ear than left ear items when attention was directed to one ear. Multiple-regression analysis was used to predict sequential processing from the dichotic data for both groups. Learning-disabled children demonstrated a substantial deficit in sequential processing as compared to normal children. These results indicate that learning-disabled children may not have adequate cerebral lateralization of receptive speech processes, shift their attention more readily, and are more inadequate in sequential processing that presumably subserves language functioning. Perhaps learning-disabled children have deficiencies of processor capacity of salient areas of the left (language) hemisphere.     

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.     

Phonemic and category encoding of unattended words in dichotic listening

The claim that unattended items in dichotic listening are categorized (Smith & Groen, 1974) was examined in three experiments using dichotic presentation and probe reaction time. Negative probe words from the unattended list were more difficult to reject when the dichotic lists shared a semantic category than when they differed in category, whether or not the attended list was precued, thereby replicating and extending Smith and Groen’s findings. The difficulty with intralist probes following dichotic lists of a homogeneous category was found to be a special case of the probe similarity effect, since extralist probes of the same category as the attended input were rejected more slowly (and with more errors) than different category probes. The effects of category homogeneity were evident on the attended, but not on the unattended, inputs (Experiment 2). The third experiment compared focused and divided attention with dichotic lists of unrelated items. Phonemically similar probes were more difficult to reject when related to items on the attended channel in the focused condition than either channel in divided attention, and easiest to reject when similar to an unattended item. Linear regression confirmed that the unattended input was processed only at a precategorical (acoustic) level.     

Preattentive control of serial auditory processing in dichotic listening

Dichotic listening performance was examined in an auditory selective attention task where subjects responded to occasional consonant-vowel (CV) or shaped broadband noise-burst (NB) targets in rapid serial auditory presentation (RASP). Trial types were randomized and included monaural CVs and NBs as well as dichotic CV-CV and CV-NB pairings. CVs were spoken by two different voices (male and female), and the two NB stimuli differed in their filter slopes at higher frequencies. The target was designated by stimulus category (/ba/, /da/, /ga/, or NB) and voice (e.g., "female /ba/"). Performance was compared for targets in the left and right ears on monaural and dichotic trials using accuracy and reaction time (RT) measures. Right ear advantages (REAs) were present for CV targets with either CV or NB distractors, but not for monaural CVs. The REA found for monaural NB targets was eliminated by CV distractors, yielding a left ear advantage (LEA) for the distractor effect of CVs on NB targets. The pattern of results suggests initial preprocessing of speech stimuli through phonetic feature analysis, followed by serial attentional processing of the objects in the auditory field. REAs are attributed to a rightward asymmetry in the preattentive control of auditory attention similar to that found in visual search.     

Expectancy effects: cost-benefit analysis of monaurally and dichotically presented speech

In three experiments, cost-benefit analysis was used to determine the role of attention in the processing of auditory information. In two experiments consonant-vowel syllables were presented monaurally, while in the third the mode of presentation was dichotic. For all three experiments the ability to detect a target stimulus under conditions in which precued location information was valid or invalid was contrasted with detection in a neutral condition where no location information was provided. The results indicated that attention can be effectively deployed under monaural conditions when either a simple detection or a discriminative response is required. Similar conclusions cannot be reached when considering the effectiveness of attention under conditions of dichotic listening. These results are discussed in relation to accounts which argue that dichotic listening performance is critically dependent upon auditory disembedding and where attention is viewed as a late process involving response selection.