Absolute Phase Uncertainty in Sinusoidal Grating Detection.
Abstract
Spatial phase plays an important role in the characterization of images and other visual patterns. Despite this, relatively few experiments have investigated the role of phase per se in human vision. Recent studies have shown that human observers are more sensitive to sinusoidal grating patterns when they have prior knowledge of the pattern's absolute phase than when they do not. They concluded that observers act as phase sensitive detectors at least some of the time. Two sinusoidal grating detection experiments were carried out to extend these results. Absolute signal phase was either held constant or varied randomly across trials. On half of random-phase trials, observers were shown a sinusoidal grating cue which revealed the absolute phase of the test signal for that trial. There were three major findings. First, consistent with previous findings, detection performance in both experiments was substantially better when phase information was provided than when it was not. Second, information about signal phase was provided equally effectively by holding phase constant over all trials within a testing block (as in the constant phase conditions) or by providing an explicit phase cue 250 ms before each trial when phase was varying randomly from trial to trial. Third, a phase cue presented 250 ms after the test pattern offset led to performance intermediate between the superior constant-phase condition and the inferior uncued random phase condition. In other words, observers were able to use phase information even when it was presented in a post-cue. The findings are discussed in terms of alternative phase-sensitive detection models.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1986
- Accession Number
- ADA176343
Entities
People
- James H. Howard Jr.
- Kevin Richardson
Organizations
- The Catholic University of America