No description available.

According to Feature Integration Theory (Treisman & Gelade, 1980), search for a target defined by features on two different dimensions (e.g. green horizontal target among red horizontal and green vertical distractors) is conducted via serial attentive search of all items in the array. Results presented in this thesis clearly demonstrate that conjunction search is not conducted as a serial self-terminating search, and suggest that subjects selectively search a single feature set. Strong support is also provided for the role of local grouping processes in visual conjunction search. This includes evidence demonstrating: (1) that local context is an important factor in directing search toward the target, and (2) that groups of spatially adjacent homogeneous elements can be processed in parallel. These results point to the importance of spatial layout of target and distractor elements. More recent theories (e.g. Cave & Wolfe, 1990) will have to be amended in order to account for these data.

No description available.

No description available.

The purpose of this study was to develop a valid and reliable measure of ability to render pictorial depth. The instrument, which was named the Pictorial Depth Rendering Test, is hereafter referred to as the PDRT.The instrument is a drawing completion test containing twenty-one pictures. Each picture is a simplified line drawing of one or more familiar objects located in pictorial space through the use of monocular depth cues. Written instructions that appear with each of the drawings ask for additional visual information to be added to the pictures. The twenty-one pictures contain a total of thirty-six scoring items providing a total possible score of thirty-six. A written set of scoring instructions was also developed for the instrument.In a pilot study the test was administered to a convenience sample of sixty subjects with an age range of seven through twenty-five. The sample was divided into six groups: lower elementary; upper elementary; junior high; senior high; college non-art students, and college art majors. To determine concurrent validity of the instrument, subjects were administered two other perceptual tests: MacGregor's Perceptual Index, and Silhan's SpatialIllusionism Sensitivity Test. Significant correlations were obtained between scores on all three tests, and scores on the PDRT were also found to correlate highly with age and grade. A high correlation of .99 was found between two sets of PDRT test scores obtained from two independent test scorers. An item discrimination index was computed on the pilot study data and four items were found to be moderate, low, or non-discriminators. The pictures containing the four items were subsequently redesigned.In the main study, the refined version of the PDRT and the Spatial Illusionism Sensitivity Test were administered to a sample of 309 elementary, secondary, and college students divided into six groups: first and second grade; fourth and fifth grade; junior high school; senior high school; college non-art, and college art majors. The perceptual Index was administered to a random sample of sixty subjects were composed of ten randomly selected students from each of the six groups. A .90 correlation was obtained between scores on correlation was obtained between scores on the PDRT and scores on the Spatial Illusionism Sensitivity Test. Significant correlations were also found between scores on the PDRT and the age and grade variables. No significant relationship was obtained between the sex variable and scores on the PDRT, although group mean scores indicated that male subjects tended to score more highly than female subjects on all three tests.The main study data were subjected to one way analysis of variance and the F-ratio obtained indicated that significant differences exist among group mean scores on the PDRT. A linear progression of PDRT group mean scores was also noted.A second item discrimination index was computed on the PDRT scores of the random sample of sixty subjects drawn from the main study sample. The D-values obtained from the second item analysis revealed that the refined version of the test contains thirty-five high discriminating items and one moderate discriminating item.A Kuder Richardson (KR-20) correlation coefficient of .90 which was obtained for the total main study PDRT data indicated that the instrument has a high level of internal reliability. Subsequent KR-20 correlations which were computed for each of the six groups revealed that the test does not have a high level of reliability when administered to lower elementary students.From the results of the study, the researcher concluded that the refined version of the PDRT contains sufficiently high levels of validity and reliability to permit its use as a measure of ability to render pictorial depth when administered to fourth grade or above.

The present thesis reports psychophysical and modeling studies on the spatial properties of visual mechanisms mediating the perception of mirror symmetry in human vision. In a first set of experiments, patterns were filtered for power spectra that decayed with spatial frequency according to variable slopes. Results revealed that symmetry detection is optimal if contrast energy is roughly equated across log-frequency bands (i.e. 1/f2) and that, under such conditions, spatial scales contribute equally and independently to symmetry perception. In a second study, random-noise patterns were filtered for various orientation bands. Results showed that symmetry perception is possible at all orientations, is mediated by oriented mechanisms, and is computed independently in different orientation channels. Data also revealed that the dimensions of the spatial integration region (IR) for symmetry vary with orientation in a way that approximately matches the spatial distribution of information in the stimulus. Finally, symmetry detection was measured for bandpass textures of variable spatial density and variable contrast polarity. For such patterns, it was found that symmetry is computed at a spatial scale proportional to stimulus density and that mechanisms insensitive to contrast polarity (i.e. second-order) are involved in the scale-selection process. / Overall, results from empirical and modeling work revealed an intimate link between symmetry perception and the properties of spatial filters. In particular, I argue that the size of the IR tends to vary such that a fixed amount of information is integrated irrespective of the spatial properties of the stimulus. Implications for the functional architecture of symmetry perception are discussed, and a paradigm for future research in symmetry perception is proposed in which spatial filtering is extended to higher orders of spatial complexity.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1982. / Bibliography: leaves 109-118. / Microfiche. / x, 118 leaves, bound ill. 29 cm

Typescript. / Bibliography: leaves 145-160. / xvii, 324 l graphs, tables

Thesis (M.A.)--York University, 2006. Graduate Programme in Psychology. / Typescript. Includes bibliographical references (leaves 89-93). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR19699

Thesis (Ph.D.)--Tufts University, 1988. / Submitted to the Dept. of Engineering Design. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;