John Palmer

jpalmer@u.washington.edu
Research Professor, Psychology

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Not taking students autumn 2007

The study of visual attention addresses two main phenomena: divided and selective attention. In vision, divided attention concerns the consequences of presenting multiple visual stimuli rather than a single stimulus. For example, a button on a web page might be easy to find on its own, but more difficult to find in a crowded display with many elements. Selective attention concerns the degree to which one visual stimulus can be processed and others ignored. For example, how well can one read the next word in this sentence and ignore the words surrounding the relevant word? Research in the Palmer lab focuses on the quantitative measurement of attentional effects on behavior. These measurements are then used to test alternative theories. Much of the prior work has used psychophysical procedures and visual search to quantify effects of divided attention. For simple stimuli, the results has been consistent with noise reduction accounts of the effects of divided attention. Such an account is also consistent with the "biased competition theory" that has been applied to much physiological research on attention. Research in the lab also addresses selective attention. In particular, we seek to measure the attentional "spatial tuning function" in a way that can be used for both behavior and neural activity.

An additional research focus is a collaboration with Dr. Mike Shadlen on decision. The Shadlen lab studies the neural basis of perceptual decisions by measuring behavior and single-unit neural activity in monkeys. Our collaboration is making a close comparison in the behavior of humans and monkeys for perceptual decisions. In particular, we seek mathematical models that can describe both behavior and neural activity. Current studies are examining how perceptual decisions are affected by difficulty, bias and speed stress.