Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 85-88).

Thesis (M.Sc.)--York University, 2005. Graduate Programme in Kinesiology and Health Science. / Typescript. Includes bibliographical references (leaves 52-58). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11748

Thesis (Ph.D.)--Boston University. / Discrimination without awareness of the stimuli being responded to has been observed in a number of different experimental situations. In the classic case, the subject is instructed to relax or to engage in what is essentially a task of imagination, while incidental stimulation is presented at a level of intensity or duration such that he remains unaware of its presence. Responses of some comparatively unrestricted type are collected and analyzed for effects attributable to the stimulation. Present interest is in the case where the subject is effortfully attending to an objective task of discrimination. His range of possible responses to the task is quite narrow, and he is required to respond almost at once. The incidentally supplied stimulation is of a novel class, different from the stimulus material of the attended task; it is such as to present directly one of the possible task responses. The method used was an adaptation of a psychophysical judgment procedure, with individual subjects viewing the materials in a tachistoscope. A rectangular patch of standard size was presented first, followed in a few seconds by a test patch of variable size; the subject was required to report whether the latter was greater or smaller than the standard. A brief, unnoticed flash preceding the test patch carried the word greater or smaller or a nonsense control stimulus. A first experiment, using only three subjects, failed to yield any evidence of influence upon the judgments due to the unnoticed incidental words. In the second experiment, 32 subjects participated. The duration of the incidental flash waa gradually increased until the subject reported noticing its presence. Statistical analysis was restricted to the last 40 responses obtained at duration levels lower than the level at which recognition occurred. For the test patch of the same size as the standard (which had been presented on 24 of the 40 trials), it was clear that some subjects had indeed been influenced in the direction of agreeing with the unnoticed greater or smaller. The effect was statistically significant over all 32 subjects. About ten achieved a high degree of agreement with the incidental word, while the agreement scores of the others were distributed in approximately a chance fashion. Agreement was not influenced by sex of the subject. Four other test patches were of sizes greater or smaller than the standard. For two of these patches, subjects responded more accurately following the appropriate flash of greater or smaller than following the nonsense flash. No consistent relationships were found between latency of responding and agreement with the flashed stimulus. It is concluded from the main result that attended judgments of objective matters are (among some individuals) subject to influence from unreportable stimulation which directly presents the response to be used. This implies some necessary modification or extension of remarks made by Klein and others relative to this point. While attention usually acts to exclude activations which would be consciously rejected as inappropriate, such activations do (among some individuals) in a significant number of cases influence attended behavior without becoming conscious. A tentative conceptualization of the process is presented, based on psychoanalytic considerations by Kris and Fisher.

Visual crowding is a dramatic breakdown of object recognition that has been studied extensively as a gateway to determine the mechanisms that underlie normal object recognition. Despite numerous proposed models and mechanisms, a unifying account has yet to be found. Proposed mechanisms reach from purely hierarchical, bottom-up accounts that place crowding early in the processing stream, to high-level attention-based accounts that allow for recurrent processing and top-down feed-back. The aim of the current work was to investigate a range of factors that would help to differentiate between these accounts. Firstly, object-category was studied as a factor that would be expected to modulate crowding if the phenomenon were to affect object recognition during several stages along the processing stream. Secondly, knowledge was studied as a possible source of top-down feedback that, if found to have a direct influence on crowding, would provide evidence against a purely hierarchical account for object recognition. Thirdly, anticipation of flanker-presence was studied as a factor modulating volitional attention-allocation. Observing an influence of anticipation on object recognition under the influence of crowding, would provide support that crowding may be the result of a limitation to focus attention. Finally, object-familiarity was studied as another factor that may modulate crowding via top-down feedback. Of these factors, only object-familiarity was found to have an influence on visual crowding. However, instead of being the result of top-down feedback, hard-wired pathways developed based on repeated exposure might explain the effect of object-familiarity. In summary, none of the studied factors provided univocal evidence to suggest that crowding were to occur at multiple levels of object recognition, or that crowding were to be influenced by higher-level effects. Hence, it may be concluded that a purely hierarchical bottom-up account is sufficient to account for the effects visual crowding exerts on normal object recognition.

The question is addressed of whether the perception of a form is exclusively determined by a prior analysis of its elements, and two major paradigms are reviewed, viz., Gestalt and information processing. Three experiments were carried out. Experiment 1 employed a signal detection task to test the hypothesis that embedding a line segment feature in a unitary figural context would facilitate its detection. The contextual effect found falsified the theory of a one-way causation between analysis of figural elements and form perception. Experiment 2 showed that a necessary condition of this context effect on feature detection is the three-dimensionality of the unitary context. With bi-hemiretinal stimulus presentation Experiment 3 showed a significant context effect in the RVF, but not in the LVF. Some current paradigms are applied to these results; it is argued concurrently that the explanation of phenomena called "perceptual" entails the solution of two problems:, that of determining what constitutes such an explanation, and an adequate theory of the experiential aspect of perceptual phenomena. These are addressed in Appendices A and B. / Arts, Faculty of / Psychology, Department of / Graduate

No description available.

No description available.

No description available.

No description available.

No description available.