SSHRC
2006-2010

Perception of 3D structure and surface properties across the visual field

Gurnsey, R.

This research seeks to explain as many visual phenomena as possible in terms of low-level mechanisms participating in the upward flow of information from eye to brain. Mechanisms studied are ones that encode local spatial structures such as the orientations of contours, texture boundaries and symmetry, and optical flow. The characteristics of mechanisms that encode these properties are inferred through psychophysical experiments with human subjects and the construction of computational models which constitute theories of the mechanisms under study.

Mechanisms that participate in the detection of symmetry, orientation and optical flow will be studied. Particular interest is in how sensitivity to symmetry and orientation change when stimuli are presented to different parts of the retina. This work on optical flow focuses on a widely discussed visual illusion known as the Pinna illusion. It consists of two concentric rings of micropatterns that when made to expand on the retina seem to rotate in opposite directions. Understanding why this illusion occurs will help us understand how motion is processed under normal circumstances.

A new direction in this research concerns the ability to perceive 3D shape in peripheral vision. A substantial portion of the research that will be conducted in the next five years will deal with this issue. This is an exciting new direction because, although we know quite a bit about how sensitivity to 2D structure (e.g., symmetry and orientation) change as a function of position in the visual field, we know almost nothing about how our sensitivity to 3D structures changes in peripheral vision. So the opportunity to expand our knowledge is very great.