Contingent Capture Hypothesis Research Articles

Investigating attentional control sets: Evidence for the compilation of multi-feature control sets

Top-down control over stimulus-driven attentional capture, as postulated by the contingent capture hypothesis, has been a topic of lively scientific debate for a number of years now. According to the latter hypothesis, a stimulus has to match the feature of a top-down established control set in order to be selected automatically. Today, research on the topic of contingent capture has focused mostly on the manipulation of only a single feature separating the target from the distractors (the selection feature). The research presented here examined the compilation of top-down attentional control sets having multiple selection features. We report three experiments in which the feature overlap between the distractor and the top-down sets was manipulated on different perceptual features (e.g., colour, orientation and location). Distractors could match three, two or one of the features of the top-down sets. In line with our hypotheses, the strength of the distractor interference effects decreased linearly as the feature overlap between the distractor and the participants’ top-down sets decreased. These results therefore suggest a decline in the efficiency with which distractors involuntarily capture attention as the target-similarity decreases. The data support the idea of multi-feature attentional control sets and are discussed in light of prominent contemporary theories of visual attention.

Crossmodal attentional control sets between vision and audition

The interplay between top-down and bottom-up factors in attentional selection has been a topic of extensive research and controversy amongst scientists over the past two decades. According to the influential contingent capture hypothesis, a visual stimulus needs to match the feature(s) implemented into the current attentional control sets in order to be automatically selected. Recently, however, evidence has been presented that attentional control sets affect not only visual but also crossmodal selection. The aim of the present study was therefore to establish contingent capture as a general principle of multisensory selection. A non-spatial interference task with bimodal (visual and auditory) distractors and bimodal targets was used. The target and the distractors were presented in close temporal succession. In order to perform the task correctly, the participants only had to process a predefined target feature in either of the two modalities (e.g., colour when vision was the primary modality). Note that the additional crossmodal stimulation (e.g., a specific sound when hearing was the secondary modality) was not relevant for the selection of the correct response. Nevertheless, larger interference effects were observed when the distractor matched both the stimulus of the primary as well as the secondary modality and this pattern was even stronger if vision was the primary modality than if audition was the primary modality. These results are therefore in line with the crossmodal contingent capture hypothesis. Both visual and auditory early processing seem to be affected by top-down control sets even beyond the spatial dimension.

Contingent capture of involuntary visual attention interferes with detection of auditory stimuli.

The involuntary capture of attention by salient visual stimuli can be influenced by the behavioral goals of an observer. For example, when searching for a target item, irrelevant items that possess the target-defining characteristic capture attention more strongly than items not possessing that feature. Such contingent capture involves a shift of spatial attention toward the item with the target-defining characteristic. It is not clear, however, if the associated decrements in performance for detecting the target item are entirely due to involuntary orienting of spatial attention. To investigate whether contingent capture also involves a non-spatial interference, adult observers were presented with streams of visual and auditory stimuli and were tasked with simultaneously monitoring for targets in each modality. Visual and auditory targets could be preceded by a lateralized visual distractor that either did, or did not, possess the target-defining feature (a specific color). In agreement with the contingent capture hypothesis, target-colored distractors interfered with visual detection performance (response time and accuracy) more than distractors that did not possess the target color. Importantly, the same pattern of results was obtained for the auditory task: visual target-colored distractors interfered with sound detection. The decrement in auditory performance following a target-colored distractor suggests that contingent capture involves a source of processing interference in addition to that caused by a spatial shift of attention. Specifically, we argue that distractors possessing the target-defining characteristic enter a capacity-limited, serial stage of neural processing, which delays detection of subsequently presented stimuli regardless of the sensory modality.

Multiple attentional control settings influence late attentional selection but do not provide an early attentional filter

When one is responding to targets containing a specific feature, non-predictive peripheral cues that share this feature lead to faster responses to the target, while cues that do not contain the target feature effectively are ignored, providing evidence for the role of attentional control settings (ACSs) in the contingent capture hypothesis. It is unclear, however, at what stage of processing multiple ACSs are implemented. We took advantage of the excellent temporal resolution of electroencephalography to demonstrate that the maintenance of multiple ACSs influences later stages of attentional selection rather than providing an early attentional filter. N2pc analyses for cues and targets revealed a similar degree of spatial capture for any peripheral cue, regardless of control settings, with target P3s reflecting the application of the ACS color contingencies.

What is top-down about contingent capture?

In the present study, we explored the mechanisms involved in the contingent capture phenomenon, using a variant of the classic precuing paradigm of Folk, Remington, and Johnston (1992). Rather than keeping the target fixed over a whole block of trials (as has traditionally been done with contingent capture experiments), we encouraged participants to adopt a top-down set before each trial. If top-down attentional set determines which property captures attention, as is claimed by the contingent capture hypothesis, one would expect that only properties that match the top-down set would capture attention. We showed that even though participants knew what the target would be on the upcoming trial, both relevant and irrelevant properties captured attention (Experiment 1). An intertrial analysis (Experiments 1 and 2) showed that previous contingent capture findings may, to a large extent, be explained by intertrial priming. In addition, when participants were further forced into adopting the required top-down set (Experiments 3 and 4), irrelevant cues were suppressed, suggesting that top-down control might operate through disengagement of attention from the location of a property that does not match top-down goals. The present findings suggest that top-down control and intertrial priming make their own distinct contributions to the contingent capture phenomenon.

Can intertrial priming account for the similarity effect in visual search?

In a visual search task, a salient distractor often elongates response times (RTs) even when it is task-irrelevant. These distraction costs are larger when the irrelevant distractor is similar than when dissimilar to the target. In the present study, we tested whether this similarity effect is mostly due to more frequent oculomotor capture by target-similar versus target-dissimilar distractors ( contingent capture hypothesis), or to elongated dwell times on target-similar versus dissimilar distractors ( attentional disengagement hypothesis), by measuring the eye movements of the observers during visual search. The results showed that similar distractors were both selected more frequently, and produced longer dwell times than dissimilar distractors. However, attentional capture contributed more to the similarity effect than disengagement. The results of a second experiment showed that stronger capture by similar than dissimilar distractors in part reflected intertrial priming effects: distractors which had the same colour as the target on the previous trial were selected more frequently than distractors with a different colour. These priming effects were however too small to account fully for the similarity effect. More importantly, the results indicated that allegedly stimulus-driven intertrial priming effects and allegedly top-down controlled similarity effects may be mediated by the same underlying mechanism.

Tracking the Location of Visuospatial Attention in a Contingent Capture Paradigm

Currently, there is considerable controversy regarding the degree to which top-down control can affect attentional capture by salient events. According to the contingent capture hypothesis, attentional capture by a salient stimulus is contingent on a match between the properties of the stimulus and top-down attentional control settings. In contrast, bottom-up saliency accounts argue that the initial capture of attention is determined solely by the relative salience of the stimulus, and the effect of top-down attentional control is limited to effects on the duration of attentional engagement on the capturing stimulus. In the present study, we tested these competing accounts by utilizing the N2pc event-related potential component to track the locus of attention during an attentional capture task. The results were completely consistent with the contingent capture hypothesis: An N2pc wave was elicited only by distractors that possessed the target-defining attribute. In a second experiment, we expanded upon this finding by exploring the effect of target-distractor similarity on the duration that attention dwells at the distractor location. In this experiment, only distractors possessing the target-defining attribute (color) captured visuospatial attention to their location and the N2pc increased in duration and in magnitude when the capture distractor also shared a second target attribute (category membership). Finally, in three additional control experiments, we replicated the finding of an N2pc generated by distractors, only if they shared the target-defining attribute. Thus, our results demonstrate that attentional control settings influence both which stimuli attract attention and to what extent they are processed.

Top-down contingent capture by color: evidence from RT distribution analyses in a manual choice reaction task

According to the contingent capture hypothesis, observers can specify their control settings in advance of the target’s presentation to quickly attend to relevant target colors. Two predictions were derived from this hypothesis and tested in a manual choice response task. First, contingent capture by color was expected: capture of spatial attention by a better-matching color stimulus should be stronger than capture by a less-matching color stimulus. Second, with the control settings specified in advance, the contingent capture by color should commence early after the stimulus onset and should be evident among fast correct responses in an RT distribution. Both predictions are shown to hold true in two experiments. Results are discussed in light of contrasting evidence for saccadic instead of manual responses.

Stimulus-driven capture and attentional set: selective search for color and visual abrupt onsets.

Recent evidence suggests that attentional capture is contingent on the attentional control setting induced by the task demands (C. L. Folk, R. Remington, & J. C. Johnston, 1992). Because the experiments on which these conclusions are based can be criticized for several reasons, the contingent capture hypothesis was tested using 2 visual search tasks in which subjects searched multielement displays in which a color singleton and onset singleton were simultaneously present. Both experiments show that the contingent capture hypothesis does not hold: Irrespective of attentional set, attention was captured by the most salient singleton. The findings suggest a stimulus-driven model of performance in which selection is basically determined by the properties of the featural singletons present in the visual field.

Stimulus-driven capture and attentional set: Selective search for color and visual abrupt onsets.

Recent evidence suggests that attentional capture is contingent on the attentional control setting induced by the task demands (C. L. Folk, R. Remington, & J. C. Johnston, 1992). Because the experiments on which these conclusions are based can be criticized for several reasons, the contingent capture hypothesis was tested using 2 visual search tasks in which subjects searched multielement displays in which a color singleton and onset singleton were simultaneously present. Both experiments show that the contingent capture hypothesis does not hold: Irrespective of attentional set, attention was captured by the most salient singleton. The findings suggest a stimulus-driven model of performance in which selection is basically determined by the properties of the featural singletons present in the visual field.