Attention

 

In one of our lines of attention research, subjects repeatedly (hundreds of times) search through an unchanging display to verify that the individual items composing the display are present.  Each item in the display serves as a search target equally often; the targets are always present (absent items comprise a different set).  Yet even after hundreds of trials, subjects take increasingly more time to verify that a target is present with increasingly larger displays (2-8 items).  Others have taken these results as evidence that visual search is memory-free, that observers must search for the target each time they are probed.  On this view, the more items one must search through, the longer it will take.  We are examining an alternative interpretation: that memories for multiple target locations exist for each display, and that competition among these potential target locations must be resolved before observers can verify the presence of the target (Skow & Peterson, VSS, 2005).

 

In a second line of attention research, we are investigating inhibition of return (IOR; Skow-Grant, Rauschenberger, & Peterson, submitted).  IOR occurs when observers are slower to respond to targets occurring in a location to which attention was previously drawn by an external cue and then withdrawn by a second external cue than to targets occurring in a previously un-cued location.  This form of IOR applies to locations.  Experiments have suggested that IOR may also apply to objects, as follows: When an object occupies the location to which attention is first drawn by the external cue, then the object moves to a new location before the second external cue appears, IOR was found at both the object’s old and the new locations.  From these effects, it has been concluded that IOR can be “object-based”  – that inhibition can be attached to, and can move with, an object.  We are investigating whether this latter conclusion is correct.