The Effects of Stimulus Orientation and Response Bias Upon Dynamic Visual Acuity.
Abstract
In experiments on dynamic visual acuity, test stimuli are characteristically presented in various orientations to the subject as they are moved across his visual field. However, current literature on static visual acuity indicates that acuity thresholds vary as a function of stimulus orientation. Static acuity thresholds are reported to be lower for the vertical and horizontal orientations, whereas, higher thresholds are found for oblique orientations. This has been referred to the 'oblique effect.' It is not known whether the same phenomonon operates in dynamic visual acuity. Hence, it is of interest to determine whether such an effect occurs under moving target conditions. The present studies utilized the up-and-down method to determine acuity thresholds for eight orientations (4 cardinal and 4 oblique) of Landolt Cs over three angular velocities. Response-bias scores were computed for each subject and compared to the threshold data. A significant orientation effect was found for both dynamically and statically presented targets, but it was not an oblique effect. That is, thresholds were not consistently higher for oblique orientations. The data further revealed a significant negative rank-order correlation between the subject's response-bias scores and their threshold scores across orientations, for dynamically presented targets. The data were suggestive that a subject's response bias contributes to the error in the measurement of psychophysically derived acuity thresholds. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 19, 1977
- Accession Number
- ADA047827
Entities
People
- Lawrence H. Frank
Organizations
- Naval Aerospace Medical Research Laboratory