Roger W. Remington

Selectivity in distraction by irrelevant featural singletons: Evidence for two forms of attentional capture.

Four experiments addressed the degree of top-down control over attentional capture in visual search for featural singletons. In a modified spatial cuing paradigm, the spatial relationship and featural similarity of target and distractor singletons were systematically varied. Contrary to previous studies, all 4 experiments showed that when searching for a singleton target, an irrelevant featural singleton captures spatial attention only when defined by the same feature value as the target. Experiments 2, 3 and 4 provided a potential explanation for the discrepancy with previous studies by showing that irrelevant singletons can produce distraction effects that are dissociable from shifts of spatial attention. The results suggest the existence of 2 distinct forms of attentional capture.

The structure of attentional control: contingent attentional capture by apparent motion, abrupt onset, and color

Five spatial cuing experiments tested 2 hypotheses regarding attentional capture: (a) Attentional capture is contingent on endogenous attentional control settings, and (b) attentional control settings are limited to the distinction between dynamic and static discontinuities (C. L. Folk, R. W. Remington, & J. C. Johnston, 1992). In Experiments 1 and 2, apparent-motion precues produced significant costs in performance for targets signaled by motion but not for targets signaled by color or abrupt onset. Experiment 3 established that this pattern is not due to differences in the difficulty of target discrimination. Experiments 4 and 5 revealed asymmetric capture effects between abrupt onset and apparent motion related to stimulus salience. The results support the hypotheses of Folk et al. (1992) and suggest that stimulus salience may also play a role in attentional capture.

Moving attention through visual space

Several experiments have shown that attention as measured by simple reaction time to luminance increments can be shifted in the visual field while the eyes are kept in a fixed position. The shift of attention appears to take place within 50 msec following a cue indicating the most likely position of the target. The present study reports that these shifts of attention can be time locked to a central cue. Moreover, they show that a probe event located between the cue and the target receives maximal facilitation from attention at a time prior to maximal facilitation at the target. These results provide support for an analogue movement of attention across the visual field that does not involve the suppression found during saccades.

Involuntary attentional capture by abrupt onsets.

The extent to which brief abrupt-onset visual stimuli involuntarily capture spatial attention was examined in five experiments. The paradigm used was intended to maximize the opportunity and incentive for subjects to ignore abrupt-onset distractor stimuli in nontarget locations. Subjects made a speeded two-choice response to a target letter appearing in one of four boxes. An abrupt-onset visual stimulus, easily discriminable from the target, was flashed briefly prior to the presentation of a target. In separate blocks, the flash stimulus marked the box in which the target would subsequently appear (SAME), a different box (DIFF), fixation (CENTER), or all four boxes (ALL). Prior to each block, subjects were informed of the flash-target relationship. In all five experiments, response time was elevated in the DIFF, CENTER, and ALL conditions. The interference effect was larger for the DIFF condition and persisted for longer flash-target SOAs. These results suggest that, under appropriate conditions, spatial attention can be involuntarily drawn to abrupt-onset events despite the intention of subjects’ to ignore them.

Moving attention - Evidence for time-invariant shifts of visual selective attention

Two experiments measured the time to shift spatial selective attention across the visual field to targets 2 or 10 deg from central fixation. A central arrow cued the most likely target location. The direction of attention was inferred from reaction times to expected, unexpected, and neutral locations. The development of a spatial attentional set with time was examined by presenting target probes at varying times after the cue. There were no effects of distance on the time course of the attentional set. Reaction times for far locations were slower than for near, but the effects of attention were evident by 150 msec in both cases. Spatial attention does not shift with a characteristic, fixed velocity. Rather, velocity is proportional to distance, resulting in a movement time that is invariant over the distances tested.

Switching Between Simple Cognitive Tasks: The Interaction of Top-Down and Bottom-Up Factors

How do top-down factors (e.g., task expectancy) and bottom-up factors (e.g., task recency) interact to produce an overall level of task readiness? This question was addressed by factorially manipulating task expectancy and task repetition in a task-switching paradigm. The effects of expectancy and repetition on response time tended to interact underadditively, but only because the traditional binary task-repetition variable lumps together all switch trials, ignoring variation in task lag. When the task-recency variable was scaled continuously, all 4 experiments instead showed additivity between expectancy and recency. The results indicated that expectancy and recency influence different stages of mental processing. One specific possibility (the configuration-execution model) is that task expectancy affects the time required to configure upcoming central operations, whereas task recency affects the time required to actually execute those central operations.

The role of input and output modality pairings in dual-task performance: evidence for content-dependent central interference.

Recent debate regarding dual-task performance has focused on whether costs result from limitations in central capacity, and whether central operations can be performed in parallel. While these questions are controversial, the dominant models of dual-task performance share the assumption that central operations are generic--that is, their interactions are independent of stimulus and response modalities. To examine these issues, we conducted a series of dual-task experiments with different input and output modality pairings. One condition combined a visual-manual task with an auditory-vocal task, and the other condition reversed the input-output pairings, combining a visual-vocal task with an auditory-manual task. Input/output modality pairings proved to be a key factor; throughout practice, dual-task costs were generally more than twice as large with visual-vocal/auditory-manual tasks than with the opposite arrangement of modalities (Experiments 1 and 2). These differences could be explained neither by competition for peripheral resources nor by differences in single-task response times (Experiment 3). Moreover, the persistent dual-task costs did not appear to stem from a central bottleneck. Contrary to the dominant models of dual-task performance, we propose that central interference between tasks depends not just on the duration of central operations, nor just strategic adaptation, but also on the content of those operations. Implications for structural and strategic accounts of dual-task interference are discussed.

Contingent attentional capture by top-down control settings: Converging evidence from event-related potentials

Theories of attentional control are divided over whether the capture of spatial attention depends primarily on stimulus salience or is contingent on attentional control settings induced by task demands. The authors addressed this issue using the N2-posterior- contralateral (N2pc) effect, a component of the event-related brain potential thought to reflect attentional allocation. They presented a cue display followed by a target display of 4 letters. Each display contained a green item and a red item. Some participants responded to the red letter and others to the green letter. Converging lines of evidence indicated that attention was captured by the cues with the same color as the target. First, these target-color cues produced a cuing validity effect on behavioral measures. Second, distractors appearing in the cued location produced larger compatibility effects. Third, the target-color cue produced a robust N2pc effect, similar in magnitude to the N2pc effect to the target itself. Furthermore, the target-color cue elicited a similar N2pc effect regardless of whether it competed with a simultaneous abrupt onset. The findings provide converging evidence for attentional capture contingent on top-down control settings.

Can new objects override attentional control settings

Previous research suggests that attentional capture by abrupt onsets is contingent on top-down attentional control settings. Four experiments addressed whether similar contingencies hold for capture elicited by the appearance of new perceptual objects. In a modified spatial cuing task, targets defined by abrupt onset or color were paired with distractors consisting of an abrupt brightening of an existing object or the abrupt appearance of a new object. In Experiments 1 and 2, when subjects searched for an onset target, both distractor types produced evidence of capture. When subjects searched for a color target, however, distractors produced no evidence of attentional capture, regardless of whether they consisted of a new perceptual object or not. Experiments 3-5 showed that the lack of distractor effects in the color-target condition cannot be accounted for by rapid recovery from capture. It was concluded that attentional capture by new objects is subject to top-down modulation by attentional control settings.

Top-down modulation of preattentive processing : Testing the recovery account of contingent capture

One highly controversial issue with respect to preattentive processing concerns the degree to which the preattentive detection of “singletons” elicits an involuntary shift of spatial attention (i.e., attentional capture) that is immune from top-down modulation. According to the “pure-capture” perspective, preattentive processing drives the allocation of spatial attention in a purely bottom-up manner, in order of relative salience. According to the “contingent-capture” perspective, preattentive processing can produce attentional capture, but such capture is contingent on whether the eliciting stimulus carries a feature property consistent with the current attentional set. Pure-capture proponents have recently argued that the evidence for contingencies in attentional capture actually reflects the rapid disengagement and recovery from capture. Two spatial cueing experiments tested the rapid recovery by measuring (1) compatibility effects associated with irrelevant distractors and (2) inhibition of return to irrelevant distractors. These two measures provide converging evidence against the rapid recovery account.