Introduction



Covert Attention Experiment	By: Ric Toploski (rtopolsk@aug.edu) Augusta State University Augusta, GA

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Introduction Task and Stimuli Design References
Introduction
Covert attention differs from overt attention in the same way that observing something out of the corner of the eye differs from gazing at it. The distinction is readily understood by students who are generally quite good at using their covert attention to focus on the really interesting stimuli in a classroom while maintaining their overt attention on the teacher. Rather than use the colloquial "out of the corner of the eye" definition for covert attention, one can use the more formal "peripheral visual and mental focus." A benefit of covert attention is that it enables us to respond more quickly to attended events, as illustrated by this experiment in which covert attention is manipulated. « Return to Top»
Task and Stimuli
The experiment is a modified version of a task employed by Posner, Nissen, and Ogden (1980). On each trial, four orange boxes appear in the corners of the screen. Initially all four boxes are equal in illumination, but after a variable delay, one of four boxes "lights up" relative to the others. The delay is measured relative to the appearance of a cue in the middle of the screen. The cue is valid, invalid, or neutral. A valid cue is an arrow that points to the side on which the illuminated box will appear. An invalid cue is an arrow pointing away from the side on which the illuminated box will appear. The neutral cue is a plus sign. The purpose of these cues is to direct the participant's covert attention. Overt attention should not change because the eyes must remain focused on the center of the screen for the participant to be able to simultaneously observe all four boxes (which are fixed via a user-controlled adjustment to appear at 7º to the right and left of center screen). The participants' task on each of the 100 trials is to identify which side the brightened box appears on as quickly and accurately as possible. In order to make shifting one's covert attentional focus advantageous, valid trials are 3 times more likely to occur than invalid trials. « Return to Top»
Design
The experiment uses a 3 X 6 within subjects design with the first variable being cue type (valid, invalid, or neutral)and the second being the delay between cue and illumination. The delays are 0, 50, 100, 200, 400, and 800 msec. The purpose of this variable is to determine when shifts of attention are most beneficial/harmful. For example, at short delays, when the arrow appears at approximately the same time as the brightened box, there should be little difference in reaction time based upon cue type since participants don't have enough time to shift. However, at longer SOA's, when the arrow appears prior to the brightened box, participants should show a benefit for valid information and a cost for invalid information. The dependent variable in the experiment is participants' speed in identifying the location-right or left-of the brightened box. « Return to Top»
References
Posner, M.I., Nissen, M.J., & Ogden, W.C. (1977). Attended and unattended processing modes: The role of set for spatial location. In H.L. Pick & I. J. Saltzman (Eds.), Modes of perceiving and processing information (pp.160-174). Hillsdale, N.J.: Erlbaum.

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