EFFECT OF CONTRAST ON THE PERCEIVED LOCATION OF BRIEFLY PRESENTED TARGETS

Title EFFECT OF CONTRAST ON THE PERCEIVED LOCATION OF BRIEFLY PRESENTED TARGETS
Author, Co-Author A. Aitsebaomo, Harold Bedell
Topic
Year
1993
Day
Saturday
Program Number
2:30 pm
Room
Salon C,D
Affiliation
Abstract In a previous study, we found that targets presented for 75 msec or less, and followed immediately by a masking stimulus, were significantly mislocalized. We concluded that this mislocalization, as well as an accompanying reduction in saccadic amplitude, resulted from a truncation of neural processing time by the mask, and was independent of target energy. It is possible, however, that the effective contrast of a short-duration target is substantially reduced by the subsequent mask, which could presumably compromise perceived target location. To investigate the role of target contrast in perceived target location, we repeated our original experiment for targets of 33 and 200 msec duration, over a range of contrasts. The targets were presented between 6 and 10 deg in the right visual field and were not followed by a mask. Using the method of constant stimuli, the subject judged whether each target presentation was left or right of a continuously present reference marker at 8 deg. Regardless of target contrast, both the 33 and 200 msec duration targets were perceived as aligned with the reference at an eccentricity very close to 8 deg. Consistent with our previous results, a 33 msec target that was followed by a mask had to be presented more than 1 deg further in the periphery to be perceived as aligned. These results support our claim that the mislocalization of short duration targets is due to a reduction in the available processing time.
Affiliation of Co-Authors
Outline