The detection threshold of a luminance-defined Gabor is improved by two high contrast, aligned flanking Gabors, an effect termed collinear facilitation. However, the neural basis of collinear facilitation is not well understood. This thesis focuses on a number of issues in collinear facilitation to better our understanding of its neural basis. (1) Cortical sites: the cortical site of collinear facilitation was investigated, and results showed that collinear facilitation is a purely monocular phenomenon. (2) Temporal properties: Collinear facilitation has fast dynamics for initiation and once collinear facilitation occurs it either decays slowly or is associated with a sustained detection. (3) Selectivity to other types of stimuli: chromatic stimuli (which isolated the S-cone opponent and the L/M cone opponent mechanisms) and 2nd order stimuli (a 2D white noise or ID noise multiplied with a Gabor envelope) were used and the results showed that collinear facilitation occurs in chromatic processing, and that some 2nd order stimuli also exhibit collinear facilitation. However, there was no interaction between luminance and chromatic systems nor between 1st and 2nd order mechanisms, suggesting independent processing streams for collinear facilitation. All of these results supported the conclusion that collinear facilitation is not a general property of cortical neurons in V1 since most V1 neurons are binocular, sensitive to both chromatic and achromatic stimuli and sensitive to both 1 st and 2nd order stimuli. Furthermore, the temporal properties of collinear facilitation suggest complex dynamic interactions, not simply explained by the passive propagation of long-range recurrent intra-cortical connections between flanks and target.

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.

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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 purpose of this study was to investigate the teaching of photography in the elementary school as a means of enhancing the development of visual awareness in children. Studies have shown that children's visual perception development can be advanced through training programs that encourage observation and responsive selection of visual stimuli. Because perceptual development is one of the goals of art education, the development of art curricula that can best account for children's perceptual growth is warranted. The photography curriculum developed in this study attempts to enhance the perceptual development of children.In Chapter I, the problem area was discussed and procedures for conducting the study were established. The problem was two-fold and questioned first whether or not a taxonomy of visual perception skills could be developed and used for the identification of educational goals and objectives, and second what black and white photographic projects should be included in a visual perceptual curriculum. Strategies were presented to insure a detailed and systematic examination of the perception and photography areas.Chapter II included an examination of the background literature pertinent to the development of the problem. The two areas covered were: 1) children's visual perceptual development, and 2) the teaching of photography. An analysis of selected perceptual theories and conditions important to the development of a taxonomy was presented in Chapter III. Due to the excessive number of perceptual theories found in the literature, only the theories of Jean Piaget, Jerome Bruner, Eleanor Gibson, James Gibson, June McFee, Viktor Lowenfeld, along with some of the theories concerning Gestalt psychology, perceptual orientation, perceptual sets, and motivation were included. None of these theories attempted to provide all the answers to perception, but each was used as an empirical base from which a taxonomy of visual perception skills was developed.In Chapter IV a taxonomy was presented for classifying the various visual perception concepts and skills into an organized structure. Taxonomic systems have been used in diverse educational situations for identifying goals and objectives. From an analysis of the visual perception literature, the major components of perception discussed by the various authors were isolated and organized into a workable list. Each component was defined and analyzed to determine similarities and differences. From the analysis the following major categories were chosen to comprise the taxonomy:1.00 Perception of Form2.00 Perception of Space3.00 Perception of Movement and Events4.00 Perception of Illusions5.00 Perception of RepresentationsFinally, in Chapter V the material presented in the previous chapters was synthesized into a photography curriculum for the elementary school. The taxonomy developed in Chapter IV was the system used for identifying the major goals and objectives required for enhancing the perceptual development of children. If the goal of art education is the development of children's visual awareness, then a properly structured photography program may provide the necessary educational experiences for this development.Based on the study and a review of the literature, the author concluded that photography can be singled out as a potentially viable method for stimulating visual awareness in children. However, photography remains one of the least understood and investigated communication mediums. Children today live in a highly visual society that constantly bombards them with instant communication media. Therefore, further investigations need to take place to reveal the educational potentialities which photography has for the elementary school curriculum.

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Experiments were conducted examining human interception of projectiles. It was found that fielders tend not maintain a linear optic trajectory (LOT) as advocated by McBeath, Shaffer, and Kaiser (1995) for interception in two-dimensions. Furthermore, it was shown that its curvature provided an ambiguous cue to action. New interception models were proposed based on optic acceleration cancellation (OAC) and the constant δ model significantly improved upon the performance of the LOT model. Awareness of interception strategy was investigated by questioning subjects about their angle of gaze variation during the ball flight. A lack of awareness of the critical information that guides interceptive behaviour was demonstrated. It is proposed that the information is stored implicitly, challenging the position of Shanks and St. John (1994). Subjects were asked to discriminate the visual information that they experienced before running to catch real balls to examine the validity of experiments that test human ability to discriminate the acceleration of simulated trajectories. Discriminative performance found to remain high even when the duration of viewed information is reduced. This intact discriminative ability led to the suggestion that trajectory discrimination occurs very rapidly after ball launch. The movement and gaze angle of fielders running to catch under conditions in which OAC cannot be sustained was analysed. Subjects showed little deviation from the strategy until the final moments of the catch. The overall conclusion to the thesis is that subjects react rapidly to the optic acceleration of a projectile to determine interceptive behaviour but may not be aware of the sensory basis of their decision and use an approximate version of the constant δ strategy to reach the interception point.