Cognitive control in the cocktail party: Preparing selective attention to dichotically presented voices supports distractor suppression

Does preparation help to switch auditory attention between simultaneous voices: Effects of switch probability and prevalence of conflict

Switching auditory attention to one of two (or more) simultaneous voices incurs a substantial performance overhead. Whether/when this voice 'switch cost' reduces when the listener has opportunity to prepare in silence is not clear-the findings on the effect of preparation on the switch cost range from (near) null to substantial. We sought to determine which factors are crucial for encouraging preparation and detecting its effect on the switch cost in a paradigm where participants categorized the number spoken by one of two simultaneous voices; the target voice, which changed unpredictably, was specified by a visual cue depicting the target's gender. First, we manipulated the probability of a voice switch. When 25% of trials were switches, increasing the preparation interval (50/800/1,400 ms) resulted in substantial (~50%) reduction in switch cost. No reduction was observed when 75% of trials were switches. Second, we examined the relative prevalence of low-conflict, 'congruent' trials (where the numbers spoken by the two voices were mapped onto the same response) and high-conflict, 'incongruent' trials (where the voices afforded different responses). 'Conflict prevalence' had a strong effect on selectivity-the incongruent-congruent difference ('congruence effect') was reduced in the 66%-incongruent condition relative to the 66%-congruent condition-but conflict prevalence did not discernibly interact with preparation and its effect on the switch cost. Thus, conditions where switches of target voice are relatively rare are especially conducive to preparation, possibly because attention is committed more strongly to (and/or disengaged less rapidly from) the perceptual features of target voice.

Preparing auditory task switching in a task with overlapping and non-overlapping response sets

We used a variant of cued auditory task switching to investigate task preparation and its relation to response-set overlap. Previous studies found increased interference with overlapping response sets across tasks relative to non-overlapping motor response sets. In the present experiments, participants classified either pitch or loudness of a simple tone as low or high, hence, both tasks were constructed around common underlying integrated semantic categories ranging from low to high. Manual responses overlapped in both category and modality for both tasks in Experiment 1A, whereas each task was related to a specific response category and response modality (manual vs. vocal) in Experiment 1B. Focusing on the manual responses in both experiments, the data showed that non-overlapping response sets (Experiment 1B) resulted in a decreased congruency effect, suggesting reduced response-based crosstalk and thus better task shielding, but at the same time switch costs were increased, suggesting less efficient switching between task sets. Moreover, varying preparation time (cue-stimulus interval, CSI) showed that long CSI led to better performance overall. Our results thus suggest that when non-overlapping response sets share common semantic categories across tasks, there is no general benefit over overlapping response sets.

The role of response set overlap for flexibility and cognitive control in auditory multitasking

We developed a new variant of auditory task-switching in order to systematically investigate shifting and cognitive control in auditory task-switching and their relation to motor response overlap in a comprehensive way. In two experiments, participants classified either pitch or loudness of a simple tone as either low or high, hence, both tasks were constructed around a common underlying dimension ranging from low to high. In Experiment 1, response sets overlapped in both category and motor modality (both manual), whereas each task was related to a specific response category and motor response modality (manual vs. vocal) in Experiment 2. The data revealed reliable switch costs that were, contrary to our expectations, not reduced with reduced response set overlap. In addition, we found reliable congruency effects and their sequential modulation in both experiments with manual as well as vocal responses, and in the absence of competing motor activation (i.e., without motor response overlap). Congruency effects after auditory task switches were smaller when response sets did not overlap. Our data thus provides an important empirical generalization of known effects to auditory stimuli as well as with both manual and vocal responses. In addition, we demonstrated that reduced congruency effects after switches for non-overlapping response sets were due to the extent of overlap between different response sets in task-switching.

Active inference, selective attention, and the cocktail party problem

In this paper, we introduce a new generative model for an active inference account of preparatory and selective attention, in the context of a classic 'cocktail party' paradigm. In this setup, pairs of words are presented simultaneously to the left and right ears and an instructive spatial cue directs attention to the left or right. We use this generative model to test competing hypotheses about the way that human listeners direct preparatory and selective attention. We show that assigning low precision to words at attended-relative to unattended-locations can explain why a listener reports words from a competing sentence. Under this model, temporal changes in sensory precision were not needed to account for faster reaction times with longer cue-target intervals, but were necessary to explain ramping effects on event-related potentials (ERPs)-resembling the contingent negative variation (CNV)-during the preparatory interval. These simulations reveal that different processes are likely to underlie the improvement in reaction times and the ramping of ERPs that are associated with spatial cueing.

Preparatory delta phase response is correlated with naturalistic speech comprehension performance

While human speech comprehension is thought to be an active process that involves top-down predictions, it remains unclear how predictive information is used to prepare for the processing of upcoming speech information. We aimed to identify the neural signatures of the preparatory processing of upcoming speech. Participants selectively attended to one of two competing naturalistic, narrative speech streams, and a temporal response function (TRF) method was applied to derive event-related-like neural responses from electroencephalographic data. The phase responses to the attended speech at the delta band (1-4 Hz) were correlated with the comprehension performance of individual participants, with a latency of - 200-0 ms relative to the onset of speech amplitude envelope fluctuations over the fronto-central and left-lateralized parietal electrodes. The phase responses to the attended speech at the alpha band also correlated with comprehension performance but with a latency of 650-980 ms post-onset over the fronto-central electrodes. Distinct neural signatures were found for the attentional modulation, taking the form of TRF-based amplitude responses at a latency of 240-320 ms post-onset over the left-lateralized fronto-central and occipital electrodes. Our findings reveal how the brain gets prepared to process an upcoming speech in a continuous, naturalistic speech context.

Distractor probability influences suppression in auditory selective attention

Auditory selective attention is thought to facilitate listening to the sound of interest (e.g., voice or music) in a noisy environment. One mechanism thought to underlie this ability is suppression of distracting stimuli. However, little is known about its operation or characteristics. We tested whether suppression in auditory selective attention capitalizes on statistical regularities in the environment to facilitate attention. Participants listened to seven-second scenes consisting of several voices speaking sequences of numbers and a distractor, which occurred more (70%) or less (30%) frequently across trials. Participants had to find the voice that was a gender singleton and report whether it was saying even or odd numbers. If suppression is an active component of auditory selective attention, task performance was expected to be better when the more frequent distractor was present. Results across the experiment and three replications revealed significantly shorter RTs when the high-probability distractor was in the scene relative to the low-probability distractor. Results are suggestive of a suppression mechanism that mitigates the detrimental influence of a frequently occurring distracting sound.

The persisting influence of unattended auditory information: Negative priming in intentional auditory attention switching

We studied negative priming (NP) in auditory attention switching. In a cued variant of dichotic listening, two spoken number words were presented, one to each ear, one spoken by a female, and one spoken by a male voice. A visual cue indicated whether the male or female voice was the target. A numerical magnitude judgement of the target number was required. The selection criterion could either switch or repeat across trials, so there were attention switch and repetition trials. Two experiments examined NP (distractor becomes target) and also included a "competitor priming" (CP) condition (target becomes distractor), relative to a "no priming" condition (target and distractor not related to previous trial). In Experiment 1, we investigated the basic priming effects. In Experiment 2, we additionally varied the response-cue interval (RCI; 100 ms vs. 1,900 ms) to examine time-related changes in priming. We found longer response times (RT) for switch trials compared with repetition trials (attention switch costs)-that is, when the internal processing context changed. In addition, we found longer RT for NP trials as well as reduced switch costs in long RCI, suggesting that previously relevant attentional settings dissipate over longer time. However, NP was not influenced by attention switches, and it was also not affected by RCI. Hence, NP in auditory attention switching does not seem strongly context or time sensitive.