Dynamics of task-set carry-over: evidence from eye-movement analyses

Exploring "phasic" vs. "tonic" accounts of the effect of switch probability on the auditory attention switch cost

Task-switching experiments have shown that the "switch cost" (poorer performance for task switches than for repetitions) is smaller when the probability of a switch is high (e.g., 0.75) than when it is low (e.g., 0.25). Some theoretical accounts explain this effect in terms of top-down control deployed in advance of the task cue ("pre-cue reconfiguration"). We tested such accounts by manipulating the time available before the onset of the cue (the response-cue interval, RCI), reasoning that top-down pre-cue reconfiguration requires time and therefore its effect should increase with RCI. Participants heard a man and a woman simultaneously speaking number words and categorised the number (< 5 vs. > 5) spoken by the voice specified by a pictorial gender-related cue presented at an RCI of 100 ms or 2,200 ms. The target voice switched with a probability of 0.25 or 0.75 (in separate sessions). In Experiment 1, RTs revealed a large effect of switch probability on the switch cost in the short RCI, which did not increase in the long RCI. Errors hinted at such an increase, but it did not receive clear statistical support and was disconfirmed by a direct and better powered replication in Experiment 2, which fully confirmed the RT pattern from Experiment 1. Thus, the effect of switch probability on the switch cost required little/no time following the response to emerge-it was already at full magnitude at a short RCI-challenging accounts that assume "phasic" deployment of top-down task-set control in advance of the cue.

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.

How Task Set and Task Switching Modulate Perceptual Processes: Is Recognition of Facial Emotion an Exception?

In Part 1 we review task-switching and other studies showing that, even with time for preparation, participants' ability to shift attention to a relevant attribute or object before the stimulus onset is limited: there is a 'residual cost'. In particular, several brain potential markers of perceptual encoding are delayed on task-switch trials, compared to task-repeat trials that require attention to the same attribute as before. Such effects have been documented even for a process often considered 'automatic' - visual word recognition: ERP markers of word frequency and word/nonword status are (1) delayed when the word recognition task follows a judgement of a perceptual property compared to repeating the lexical task, and (2) strongly attenuated during the perceptual judgements. Thus, even lexical access seems influenced by the task/attentional set. In Part 2, we report in detail a demonstration of what seems to be a special case, where task-set and a task switch have no such effect on perceptual encoding. Participants saw an outline letter superimposed on a face expressing neutral or negative emotion, and were auditorily cued to categorise the letter as vowel/consonant, or the face as emotional/neutral. ERPs exhibited a robust emotional-neutral difference (Emotional Expression Effect) no smaller or later when switching to the face task than when repeating it; in the first half of its time-course it did not vary with the task at all. The initial encoding of the valence of a fixated facial emotional expression appears to be involuntary and invariant, whatever the endogenous task/attentional set.

Serial or parallel proactive control of components of task-set? A task-switching investigation with concurrent EEG and eye-tracking

Among the issues examined by studies of cognitive control in multitasking is whether processes underlying performance in the different tasks occur serially or in parallel. Here we ask a similar question about processes that pro-actively control task-set. In task-switching experiments, several indices of task-set preparation have been extensively documented, including anticipatory orientation of gaze to the task-relevant location (an unambiguous marker of reorientation of attention), and a positive polarity brain potential over the posterior cortex (whose functional significance is less well understood). We examine whether these markers of preparation occur in parallel or serially, and in what order. On each trial a cue required participants to make a semantic classification of one of three digits presented simultaneously, with the location of each digit consistently associated with one of three classification tasks (e.g., if the task was odd/even, the digit at the top of the display was relevant). The EEG positivity emerged following, and appeared time-locked to, the anticipatory fixation on the task-relevant location, which might suggest serial organisation. However, the fixation-locked positivity was not better defined than the cue-locked positivity; in fact, for the trials with the earliest fixations the positivity was better time-locked to the cue onset. This is more consistent with (re)orientation of spatial attention occurring in parallel with, but slightly before, the reconfiguration of other task-set components indexed by the EEG positivity.

EEG Decoding Reveals the Strength and Temporal Dynamics of Goal-Relevant Representations

Models of action control assume that attentional control settings regulate the processing of lower-level stimulus/response representations. Yet, little is known about how exactly control and sensory/response representations relate to each other to produce goal-directed behavior. Addressing this question requires time-resolved information about the strength of the different, potentially overlapping representations, on a trial-by-trial basis. Using a cued task-switching paradigm, we show that information about relevant representations can be extracted through decoding analyses from the scalp electrophysiological signal (EEG) with high temporal resolution. Peaks in representational strength—indexed through decoding accuracy—proceeded from superficial task cues, to stimulus locations, to features/responses. In addition, attentional-set representations were prominent throughout almost the entire processing cascade. Trial-by-trial analyses provided detailed information about when and to what degree different representations predict performance, with attentional settings emerging as a strong and consistent predictor of within-individual and across-individual variability in performance. Also, the strength of attentional sets was related to target representations early in the post-stimulus period and to feature/response representations at a later period, suggesting control of successive, lower-level representations in a concurrent manner. These results demonstrate a powerful approach towards uncovering different stages of information processing and their relative importance for performance.

Is conflict adaptation due to active regulation or passive carry-over? Evidence from eye movements

Conflict-adaptation effects (i.e., reduced response-time costs on high-conflict trials following high-conflict trials) supposedly represent our cognitive system's ability to regulate itself according to current processing demands. However, currently it is not clear whether these effects reflect conflict-triggered, active regulation, or passive carry-over of previous-trial control settings. We used eye movements to examine whether the degree of experienced conflict modulates conflict-adaptation effects, as the conflict-triggered regulation view predicts. Across 2 experiments in which participants had to identify a target stimulus based on an endogenous cue while-on conflict trials-having to resist a sudden-onset distractor, we found a clear indication of conflict adaptation. This adaptation effect disappeared however, when participants inadvertently fixated the sudden-onset distractor on the previous trial-that is, when they experienced a high degree of conflict. This pattern of results suggests that conflict adaptation can be explained parsimoniously in terms of a broader memory process that retains recently adopted control settings across trials. (PsycINFO Database Record