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Attentional Blink in Natural Stimuli

(a collaboration with S. Makeig, Swartz Center of Computational Neuroscience, UCSD, supported by DARPA)

Humans comprehend the "gist" of even a complex natural scene within a small fraction of a second. If, however, observers are asked to detect targets in a sequence of rapidly presented items, detection of a target succeeding another target by about a third of a second is severely impaired. Remarkably, this impairment is absent if the second target immediately follows the first. These two phenomena constitute the "attentional blink" (AB; Raymond, Shapiro, & Arnell, 1992). Explanations of AB invoke an attentional "bottleneck", a capacity limited processing stage, to be involved in causing the AB. The hypothesis of a single and central bottleneck predicts that the properties of the AB, in particular its duration, would be independent of stimulus category. Since most experiments on the AB use well-controlled but artificial stimuli, the question arises whether the same phenomenon occurs for complex, natural stimuli. In our experiments we presented rapid sequences of complex stimuli and asked observers to detect and remember items of a specific category (faces, watches or both). We found a consistent AB for both target categories but the duration of the AB depended on the target category. This dependence implies that a single attentional bottleneck is unlikely to account for the AB under natural viewing conditions. In addition, this result further highlights the care that has to be taken when generalizing results obtained using simple stimuli to predictions about visual performance under more natural conditions.