The spatially global control of attentional target selection in visual search

ABSTRACT

Glyn Humphreys and his co-workers have made numerous important theoretical and empirical contributions to research on visual search. They have introduced the concept of attentional target templates and investigated the nature of these templates and how they are involved in the control of search performance. In the experiments reported here, we investigated whether feature-specific search templates for particular colours can guide target selection independently for different regions of visual space. We employed behavioural and electrophysiological markers of attentional selection in tasks with targets defined by specific colour/location combinations. In Experiment 1, participants searched for pairs of colour targets in a particular spatial configuration (e.g., red in the upper and blue in the lower visual field). In Experiment 2, they searched for single colour-defined targets at specific locations (e.g., red on the left or blue on the right). Target displays were preceded by non-informative cues containing target-colour items at task-set matching or mismatching locations. Contingent attentional capture was observed only for matching cues. However, both matching and mismatching cues elicited identical N2pc components, indicating equivalent attentional capture. This shows that the rapid deployment of attention towards target features is spatially non-selective, and that selection of colour/location combinations occurs at later post-perceptual stages. This was further corroborated in search displays where targets were accompanied by target-colour distractors at nonmatching locations. Here, spatial biases towards the target emerged late and were strongly attenuated relative to displays without such distractors. These results demonstrate that attentional templates for target-defining features operate in a spatially-global fashion. Feature-based guidance of visual search cannot be restricted to particular locations even when this is required by the demands of an attentional selection task.

KEYWORDS:

• Selective attention
• top-down control
• spatial cueing
• event-related brain potentials
• feature-based attention

Disclosure statement

No potential conflict of interest was reported by the author.

Notes

1. The presence versus absence of a colour change between cue and target displays may also have contributed to the pattern of behavioural spatial cueing effects in Experiment 2. Trials with fast RTs (valid trials with matching cues and invalid trials with mismatching cues) were trials where the cues and targets had the same colour, whereas RTs were slow on trials where there was a colour change. The reverse spatial cueing effect observed for trials with mismatching cues (and the large positive spatial cueing effects on trials with matching cues) may therefore in part also reflect RT costs associated with a colour change.

2. It should be noted that there was no main effect of Response Compatibility and no interaction between Response Compatibility and Target Display Type in Experiment 1 (both F < 1.6). This difference is presumably because responses were determined by the properties of single objects (their alphanumerical category) in Experiment 2, but depended on a relational property between two different objects (same versus different bar orientation) in Experiment 1.

Additional information

Funding

This work was supported by the Economic and Social Research Council (ESRC) UK [grant number ES/L016400/1].