Are Eye Movements the Basis for Differences in the Neurophysiological Signals of Familiar and Novel Images?
Studies in humans and monkeys have shown differences in the time spent examining novel images (e.g., Gothard et al. 2004). Studies that measure looking time traditionally involve pairs of images and a relatively long period of free viewing. This is a very different procedure from our task where images were centrally presented in sequences of a few hundred milliseconds for each image. However, even this short presentation period provides sufficient time for visual recognition and the generation of saccades. To examine the effects of eye movements on our results, we first computed for each stimulus presentation, the location of the center of gaze relative to the center of each image and determined the median position during the time the image was on the screen. We then compared these median eye positions for each data set (using those data sets where all images were shown at full contrast, n = 42) by the nonparametric rank-sum test. There was no systematic difference between eye position