Abstract
Boundary extension (BE) is an anticipatory projection of scene layout; observers remember having seen beyond the edges of a view. It has been proposed that this error of commission is adaptive — one purpose being to prime upcoming layout during visual scanning. However, this hypothesis would be discounted if the plan to fixate near a boundary resulted in fairly accurate boundary memory — a credible possibility given that spatial attention precedes a fixation. Four experiments were conducted to determine if the plan to fixate near a border influences the “shape” of the extended region moments later. Ss centrally fixated each of 20–30 photographs for 250 ms, at which point a small, superimposed cue indicated whether they should fixate an object by the left or right border, or maintain central fixation. A mask rapidly replaced the picture so that in the eye movement conditions, the picture was gone before the eyes actually landed (allowing no new information to be foveated). Boundary memory was immediately tapped using a border adjustment task: the same scene (or various alternative views) appeared and S adjusted the view by moving each boundary to reveal more or less of the scene. Results showed that the to-be-fixated boundary, and the top and bottom boundaries, all yielded boundary extension. However the side opposite the targeted boundary did not; memory reflected actual boundary placement in that case alone. Consistent with the Biased Competition Model of Attention, selection between two actions (“look left vs. right”) resulted in inhibition of processing on the side associated with the “path not taken”. The attended, to-be-fixated region, however, included an anticipated swath of layout — that could serve to prime information just beyond the original view.
NIMH R01 MH54688-04A2