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The Effect of Set Size on the Relation Between Saccadic and Perceptual Decisions During SearchWe have shown that when searching for a disk in noise at one of 10 locations, the accuracy of the I st saccade is similar to that of the perceptual decision at the time of saccadic programming. The present study has two goals: 1) to test whether this linden - extends to a contrast-discrimination task without noise, and 2) to measure the effect of set size on the relation between saccadic and perceptual decisions. Methods: Three observers searched over a grey background (34.5 cd/sq m) for a bright disk (63.2 cd/sq m) among dim disks (54.1 cd/sq m) along the circumference of a circle (r = 5.9 deg.) centered on a fixation cress. Four set sizes (2, 4, 6, 12) were used. In the 1st condition, stimuli were presented for 1 sec. and observers used natural eye movements. We then measured the accuracy of the first saccade (% correct using a shortest-distance criterion). In the 2nd condition, observers fixated a central cross at all times and the stimulus duration was approx. 70 as less than the median latency of the first saccade in the 1st condition (saccadic programming time). We then recorded perceptual performance and discarded trials in which observers broke fixation. Results: For set sizes of 2, 4, 8, and 12, the mean d' across observers for the perceptual decision was 2.03, 1.96, 1.94, 1.71, respectively, while the mean d' of the first saccade was only 0.73, 1.40, 1.23, 1.17. Conclusions: Unlike detection of a disk in noise, for all observers and set-sizes, the perceptual accuracy at the time of saccadic programming is better than that of the lst saccade. For set-sizes of 4, 6, and 12, the amount of information available to the perceptual system relative to that available to the saccadic system is approximately constant (fixed do ratio). For these higher set sizes, the constancy in do across set size for both perception and saccadic decisions is consistent with a simple signal detection theory (SDT) model that processes noisy signals in parallel. However, for 2 observers, at a set-size of 2, saccadic targeting appears to be worse than the SDT model prediction, perhaps due to speed-accuracy trade-off.
Document ID
20020054244
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Eckstein, M. P.
(NASA Ames Research Center Moffett Field, CA United States)
Beutter, B. R.
(NASA Ames Research Center Moffett Field, CA United States)
Stone, L. S.
(NASA Ames Research Center Moffett Field, CA United States)
Wenzel, Beth
Date Acquired
August 20, 2013
Publication Date
January 1, 1998
Subject Category
Behavioral Sciences
Meeting Information
Meeting: ARVO 1998 Annual Meeting
Location: Fort Lauderdale, FL
Country: United States
Start Date: May 9, 1998
End Date: May 15, 1998
Funding Number(s)
PROJECT: RTOP 199-12-06-37
CONTRACT_GRANT: NIH-RO1-HL-53455
PROJECT: RTOP 548-50-12
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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