bob.kentridge.info

Attention and Consciousness

For many years I have been interested in the relationship between attention and awareness. These processes have been seen as being intimately related from the time of William James and Willhelm Wundt. Even today the extent to which they dissociate is hotly debated both by Psychologists and Philosophers. The issue is important because if they are one and the same thing then to study consciousness all you can just study attention which is much easier to understand and measure. I was alerted to the fact that they might dissociate when studying a blindsight patient who volunteered that he would try to attend to a particular location high in the visual field because we mentioned that the stimuli he was being asked to repond to were positioned near the top of the display screen. This would not be too odd were it not for the fact that his condition rendered him blind to the stimuli he was responding to - so far as he was concerned his responses were just guesses. If attention could alter the speed or accuracy of the guesses he made about unseen stimuli then attention must be capable of affecting stimuli independently of awareness. My colleagues and I have run many experiments over the years showing this to be the case both in blindsight subjects and in normal observers. We are currently assessing whether similar dissociations apply to other forms of attention.

Geometry and Statistics of Visual Processing

I am interested in the relationship between the computational demands of processing different types of visual information and their loci in the brain. One might, for example, hypothesise that visual information varies in the extent to which it requires geometric analysis as opposed to analysis of less local statistical parameters. Estimating object shape is largely a geometric problem although it might depend to some extent on statistical analysis of shape from shading. Perceiving texture is likely to involve a greater statistical component but is still essentially a process of recovering local surface geometry. Perception of glossiness and of sub-surface scattering are both apparently governed by statistical heuristics (albeit different ones). Some (but not all) stages of colour vision depend upon comparisons of local signals to complex scene statistics. Data from both neuroimaging experiments and experiments with neurological patients suggest that overall shape, colur, texture and probably even glossiness are all processed separately.

Rebabilitating Hemianopic Dyslexia

I have examined the mechanisms underlying hemianopic dyslexia using gaze-contingent displays with a view to refining rehabilitation procedures for this condition. In future I would like to assess the extent to which hemianopes can exploit different types of visual information falling into their subjectively blind hemifields.