Eye Movements and Practice Effects in the Attentional Dwell Time Paradigm

In the attentional dwell time paradigm by Duncan, Ward, and Shapiro (1994) , two backward masked targets are presented at different spatial locations and separated by a varying time interval. Results show that report of the second target is severely impaired when the time interval is less than 500 ms which has been taken as a direct measure of attentional dwell time in human vision. However, we show that eye movements may have confounded the estimate of the dwell time and that the measure may not be robust as previously suggested. The latter is supported by evidence suggesting that intensive training strongly attenuates the dwell time because of habituation to the masks. Thus, this article points to eye movements and masking as two potential methodological pitfalls that should be considered when using the attentional dwell time paradigm to investigate the temporal dynamics of attention.

Eye movements and attention in visual feature search with graded target-distractor-similarity

We conducted a visual feature search experiment in which we varied the target-distractor-similarity in four steps, the number of items (4, 6, and 8), and the presence of the target. In addition to classical search parameters like error rate and reaction time (RT), we analyzed saccade amplitudes, fixation durations, and the portion of reinspections (recurred fixation on an item with at least one different item fixated in between) and refixations (recurred fixation on an item without a different item fixated in between) per trial. When target-distractor-similarity was increased, more errors and longer RTs were observed, accompa-nied by shorter saccade amplitudes, longer fixation durations, and more reinspec-tions/refixations. An increasing set size resulted in longer saccade amplitudes and shorter fixation durations. Finally, in target absent trials we observed more reinspections than refixations, whereas in target present trials refixations were more frequent than reinspec-tions. The results on saccade amplitude and fixation duration support saliency-based search theo-ries that assume an attentional focus variable in size according to task demands and a vari-able attentional dwell time. Reinspections and refixations seem to be rather a sign of in-complete perceptual processing of items than being due to memory failure.

Attention Dependency in Implicit Learning of Repeated Search Context

How much attention is needed to produce implicit learning? Previous studies have found inconsistent results, with some implicit learning tasks requiring virtually no attention while others rely on attention. In this study we examine the degree of attentional dependency in implicit learning of repeated visual search context. Observers searched for a target among distractors that were either highly similar to the target or dissimilar to the target. We found that the size of contextual cueing was comparable from repetition of the two types of distractors, even though attention dwelled much longer on distractors highly similar to the target. We suggest that beyond a minimal amount, further increase in attentional dwell time does not contribute significantly to implicit learning of repeated search context.