Roles of chromatic and luminance information in pattern recognition
Abstract
Do chromatic changes supply perceivers with different information for recognizing objects from luminance changes? This study seeks to answer this question in the case of two-dimensional pattern recognition. Experiment 1 tested the hypotheses that luminance changes are used by the visual system to perceive an edge, and chromatic changes are used by the visual system to perceive a region, and also to perceive an edge at some level. Experiment 2 evaluated whether results of Experiment 1 were specific to the particular spatial frequency contents of the stimuli had. Experiment 3 tested the same hypotheses evaluated in Experiments 1 and 2, using a different manipulation. The subject's task was to compare a pattern defined by chromaticity or luminance to the standard pattern. In Experiments 1 and 2, I evaluated the disruptive effects of two types of degradation: (1) degradation of a pattern's edges, and (2) degradation of a pattern's region. Degraded areas looked as if they were occluded by small squares and/or rectangles whose color was identical to the background. One way to recognize a 2-D pattern is through the perception of its edges. If degradation of the edges by luminance (or chromaticity) harms comparative judgments, then luminance (or chromaticity) is used to perceive those edges. Similarly, another way to recognize a 2-D pattern is through the perception of its central region. If degradation of the region by chromaticity harms comparative judgments, then chromaticity is used to perceive that region. In Experiment 3, I degraded a comparison pattern's profile. To degrade edge information, I placed additional edges around the comparison pattern to make the pattern's edge gradual rather than sharp. To degrade region information, I eliminated the smooth continuity by inserting intermediate colors or inserting the background color. The performance in each degradation condition was compared with baseline. The results obtained in this series of experiments confirmed the main hypotheses: the visual system identifies edges using luminance changes, although chromaticity may also be used for edge identification; the visual system identifies region though chromatic changes. Whether spatial frequency alone can account for these results will be discussed.
Degree
Ph.D.
Advisors
Melara, Purdue University.
Subject Area
Psychology|Experiments|Cognitive therapy
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.