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Lisa N. Jefferies, Vincent Di Lollo; Temporal dynamics in the expansion and contraction of the attentional window. Journal of Vision 2007;7(9):808. doi: 10.1167/7.9.808.
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© ARVO (1962-2015); The Authors (2016-present)
The vast amount of visual information in the world necessitates a selective mechanism that limits visual processing to objects or locations of interest. Visual attention fulfils this selective function, and may be allocated with varying degrees of success over tasks, space, and time. We propose a qualitative model that accounts for the modulation of the spatial extent of the focus of attention across time, and we test that model in a series of experiments. Specifically, we employed the Attentional Blink (AB) and Lag-1 sparing, to test the spatiotemporal modulations of attention. When two sequential targets are inserted in a rapid stream of distractors, perception of the second target is impaired at short inter-target lags (AB deficit). Paradoxically, this deficit disappears when the second target appears directly after the first (Lag-1 sparing). Lag-1 sparing always occurs when the two targets appear in the same spatial location, but occurs to targets in different spatial locations only if the focus of attention encompasses both locations. Given this, the incidence and magnitude of Lag-1 sparing provides a sensitive measure of the degree to which the focus of attention encompasses the location of the second target. The present research utilized two simultaneous distractor streams to measure our ability to shift and expand spatial attention over time. Two main findings emerged: first, when the second target appeared directly after the first, there was a progressive transition from Lag-1 sparing to AB deficit as the SOA between successive items was increased. This provides a measure of the spatiotemporal modulations of the focus of attention. Second, the change from Lag-1 sparing to AB deficit was related linearly to SOA. This strongly suggests that the spatial extent of attention varies linearly over time and that the expanding and shrinking of the focus of attention may be analog in nature.
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