Electrophysiological indices of target and distractor processing in visual search

Attentional selection of a target presented among distractors can be indexed with an event-related potential (ERP) component known as the N2pc. Theoretical interpretation of the N2pc has suggested that it reflects a fundamental mechanism of attention that shelters the cortical representation of targets by suppressing neural activity stemming from distractors. Results from fields other than human electrophysiology, however, suggest that attention does not act solely through distractor suppression; rather, it modulates the processing of both target and distractors. We conducted four ERP experiments designed to investigate whether the N2pc reflects multiple attentional mechanisms. Our goal was to reconcile ostensibly conflicting outcomes obtained in electrophysiological studies of attention with those obtained using other methodologies. Participants viewed visual search arrays containing one target and one distractor. In Experiments 1 through 3, the distractor was isoluminant with the background, and therefore, did not elicit early lateralized ERP activity. This work revealed a novel contralateral ERP component that appears to reflect direct suppression of the cortical representation of the distractor. We accordingly name this component the distractor positivity (

The attentional blink: Invreasing target salience provides no evidence for resource depletion. A commentary on Dux, Asplund and Marois

The authors have argued elsewhere that the attentional blink (AB; i.e., reduced target detection shortly after presentation of an earlier target) arises from blocked or disrupted perceptual input in response to distractors presented between the targets. When targets replace the intervening distractors, so that three targets (T1, T2, and T3) are presented sequentially, performance on T2 and T3 improves. Dux, Asplund, and Marois (2008) argued that T3 performance improves at the expense of T1, and thus provides evidence for resource depletion. They showed that when T1 is made more salient (and presumably draws more resources), an AB for T3 appears to reemerge. These findings can be better explained, however, by (1) the relationship between T1 and T2 (not T1 and T3) and (2) differential salience for T3 in the long-lag condition of Dux et al.'s study. In conclusion, the Dux et al. study does not present a severe challenge to input control theories of the AB. © 2009 The Psychonomic Society, Inc

Dos and don’ts in response priming research

Response priming is a well-understood but sparsely employed paradigm in cognitive science. The method is powerful and well-suited for exploring early visuomotor processing in a wide range of tasks and research fields. Moreover, response priming can be dissociated from visual awareness, possibly because it is based on the first sweep of feedforward processing of primes and targets. This makes it a theoretically interesting device for separating conscious and unconscious vision. We discuss the major opportunities of the paradigm and give specific recommendations (e.g., tracing the time-course of priming in parametric experiments). Also, we point out typical confounds, design flaws, and data processing artifacts