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Copyright 2012 Aileen M. Echiverri-Cohen - University of Washington

Copyright 2012 Aileen M. Echiverri-Cohen - University of Washington

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lower rates <strong>of</strong> correct identification <strong>of</strong> the second target under Lag 2 and 3 conditions (e.g., one<br />

or two distractors presented between targets). With more than two intervening distractors,<br />

participants are again able to correctly identify both targets under Lag 4 and 5 conditions. This is<br />

termed an "attentional blink," referring to a deficit in the ability to identify a second target <strong>of</strong> a<br />

pair <strong>of</strong> stimuli presented closely in time. This is thought to happen because the presentation <strong>of</strong><br />

two or more distractors allows the participant to recover from the impairment in attention.<br />

Accordingly, when plotting accuracy <strong>of</strong> identification <strong>of</strong> the second target (T2), a U-shaped<br />

pattern emerges as a function <strong>of</strong> length <strong>of</strong> lag.<br />

Cognitive models <strong>of</strong> AB that explain this U-shaped pattern fall into two categories: early<br />

(attentional gating model; Weighselgartner & Sperling, 1987; inhibition model, Raymond, et al.,<br />

1992) or late selection (two-stage processing model; Chun & Potter, 1995, interference model;<br />

Shapiro, Raymond, & Arnell, 1994). Both highlight the limitations in processing two targets<br />

close in time within a stream <strong>of</strong> stimuli (Peterson & Juola, 2000). Early selection refers to the<br />

recruitment <strong>of</strong> attentional resources in the early stage <strong>of</strong> visual processing initiated by the<br />

processing resources needed in the identification <strong>of</strong> the first target that leads to poor<br />

identification <strong>of</strong> the second target. In contrast, with late selection, attentional resources are<br />

recruited by an item in the distractor position immediately following the first target leading to<br />

limited resources in processing the second target. Although more studies are consistent with late<br />

selection (e.g., Vogel, Luck, & Shapiro, 1998, Vogel & Luck, 2002; Di Lillo et al., 2005) than<br />

early selection theories (e.g., Giesbrecht & Kingstone, 2004), others show that attentional<br />

mechanisms may operate at multiple levels <strong>of</strong> perception. Indeed, recent studies have adopted a<br />

connectionist model that suggests that both perceptual and post-perceptual level selection in AB<br />

can occur (Bowman & Wyble, 2007; Giesbrecht et al., 2009), depending on task demands (e.g.,<br />

8

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