Poster A116, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Behavioral Oscillations in Perceptual Organization
Gideon Caplovitz1, Gennady Erlikhman1; 1Department of Psychology, University of Nevada Reno
Oscillatory patterns of brain activity at different frequencies are known to interact with perceptual processes. Following several recent behavioral studies in the domain of attention, we demonstrate that rhythmic patterns also exist in perceptual behaviors without explicit stimulus entrainment. Oscillations in reaction time and accuracy at 7Hz (theta-band) and 10-12Hz (alpha-band) have been previously linked to sensory and attentional processes respectively. However, virtually all studies have used an attentional cuing paradigm and so the exact relationship between oscillations in behavior and cognitive processes remains unclear. In a series of experiments, subjects performed a fat/thin illusory contour discrimination task which was followed by two successive masks. The interval between the two masks ranged from 16.7 ms – 533.3 ms in steps of 16.7 ms. Discrimination accuracy fluctuated by as much as 15% as a function of the inter-mask interval. Oscillations were observed at frequencies of 4-7 Hz, 9-12 Hz, and 20-24 Hz. These effects persisted regardless of whether the 2nd of the two masks were local (disrupting local perceptual processes) or global (disrupting illusory contour perception processes), suggesting that the oscillations did not reflect feedforward completion or feedback masking processes. The effects also persisted when a 2-interval forced-choice paradigm was used, indicating that the fluctuations in behavior were due to variations in the perception of the stimulus and not in response choice. Despite not having an explicit attentional cue, we hypothesize that the observed behavioral fluctuations reflect the rhythmic nature of perceptual sampling.
Topic Area: PERCEPTION & ACTION: Vision