Introduction

Covert Attention Experiment

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

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»

Data Format in Downloadable csv file
The data obtained via the Download data link on the PsychExperiments homepage are comma delimited. The first entry (up to the first comma) is the affiliation of the research participant. Typically this is the class to which the participant belongs. Non-affiliated participants use the default entry of Interested Person. Next is the randomly assigned ID code for the research participant. The third entry is the date. The fourth is a measure of "experiment time" in seconds. This is how long it took the participant to complete the experiment, beginning with Trial 1 and ending with the last trial. (Time spent reading instructions etc. are not included). The measure is useful as a screen for "bad" data. The time measure should be appropriate to the task--not too fast and not too slow. The fifth entry "T" is a space holder. Normally subject data would appear here but none were collected in this experiment. Next are the raw data for the experiment organized by trial number. Trial numbers are from 1 to 100. After the trial number is a text entry to indicate whether the cue was valid, invalid, or neutral. Next is a number to indicate in milliseconds the delay time. Next is a response time measure in seconds, followed by a text entry indicating whether the choice was correct or incorrect. Each of these entries is separated by a comma. The table below shows the format trial data in tabular form. Not included in the tabular display are the user information (affiliation, ID, date, and experiment time) which precede these data, as shown in the text line below the table.

Trial No.	Cue	Delay (msec)	RT (sec)	Choice	Trial No.	Cue	etc
1,	valid,	100,	2.958,	Correct,	2,	valid,

Indiana University (Purdue)--Johnsons Cognition,RYO585,11/10/2004,427,T,1,valid,100,2.958,Correct,2,valid,100,2.784,Correct

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.