From Capture to Inhibition: How does Irrelevant Information Influence Visual Search? Evidence from a Spatial Cuing Paradigm

Abstract

Even though information is spatially and temporally irrelevant, it can influence the processing of subsequent information. The present study used a spatial cuing paradigm to investigate the origins of this persisting influence by means of event-related potentials (ERPs) of the EEG. An irrelevant color cue that was either contingent (color search) or non-contingent (shape search) on attentional sets was presented prior to a target array with different stimulus-onset asynchronies (SOA; 200, 400, 800 ms). Behavioral results indicated that color cues captured attention only when they shared target-defining properties. These same-location effects persisted over time but were pronounced when cue and target array were presented in close succession. N2 posterior contralateral (N2pc) showed that the color cue generally drew attention, but was strongest in the contingent condition. A subsequently emerging contralateral posterior positivity referred to the irrelevant cue (i.e., distractor positivity, Pd) was unaffected by the attentional set and therefore interpreted as an inhibitory process required to enable a re-direction of the attentional focus. Contralateral delay activity (CDA) was only observable in the contingent condition, indicating the transfer of spatial information into working memory and thus providing an explanation for the same-location effect for longer SOAs. Inhibition of this irrelevant information was reflected by a second contralateral positivity triggered through target presentation. The results suggest that distracting information is actively maintained when it resembles a sought-after object. However, two independent attentional processes are at work to compensate for attentional distraction: the timely inhibition of attentional capture and the active inhibition of mental representation of irrelevant information.

Keywords: CDA; N2pc; cognitive control; distractor positivity; visual selective attention.

Figure 1

Example of the experimental design used for the current study. Participants had to report the gap position of the colored Landolt C (red, green, blue or yellow, here depicted in red) or the gray Landolt square that were presented among five gray Landolt Cs. Prior to target array onset a task-irrelevant cue array was presented for 50 ms followed by a randomly varying stimulus onset asynchrony (SOA; duration 200, 400 or 800 ms). The cue array was composed out of six stimuli with a colored singleton cue (red, green, blue or yellow, here depicted for the red condition) presented among five gray stimuli. Cue singletons and target singletons were randomly presented at the four lateralized positions. Thus, in 25% of the trials cue and target shared the same location.

Figure 2

Behavioral results depending on stimulus-onset asynchronies (SOA) conditions and cue target location. Response times and error rates are separately shown for the color (A) and the shape (B) task.

Figure 3

Event-related potentials (ERPs), time-locked to cue array onset at posterior electrodes (PO7/PO8) for each SOA condition are separately shown for the color and the shape task. Contralateral and ipsilateral waveforms are depicted relatively to the side of the color singleton cue (A–F). The lower row shows the difference waves (event related lateralizations, ERLs) for the color (G) and the shape (H) task. Time points of the cue and the target array are highlighted in gray.

Figure 4

Topographies from the ERLs during the time interval of N2pc (180–280 ms) (A,B), Pd-early (300–400 ms) (C,D), Pd-late (500–600 ms) (E,F) and CDA (600–800 ms) (G,H) separately depicted for the color and the shape task.

Figure 5

Target elicited P1/N1 components. Waveforms contra- and ipsilateral to color cues presented at the same (same and vertical quadrant) (A,C) and different side (horizontal and diagonal quadrant) (B,D) with respect to the color and shape target for the 400 ms SOA.