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UBC Theses and Dissertations

A contextual effect in feature detection Womersley, Marcus David


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.

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