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UBC Theses and Dissertations

Dynamic spatial tuning of attentional focus in the attentional blink Jefferies, Lisa N.


When two sequential targets (T1, T2) are inserted in an RSVP stream of distractors, perception of T2 is impaired at inter-target lags shorter than 700 ms. Paradoxically, this deficit disappears when T2 is presented directly after T1 (Lag-1 sparing). Visser et al. (1999) found that Lag-1 sparing occurs only when T1 and T2 are presented in the same stream. In contrast, Shih (2000) obtained Lag-1 sparing with targets in separate streams. Four experiments addressed this inconsistency and revealed Lag-1 sparing with targets in different streams, but only when observers had no foreknowledge of T1' s location. We hypothesized that when T1 location is known, the attentional spotlight is focused narrowly on that stream; if T2 then appears in the other stream it is missed, and Lag-1 sparing does not occur. When T1 location is not known, the spotlight is focused broadly, encompassing both streams, and Lag-1 sparing ensues.

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