The Hilbert transform of horizontal gaze position during natural image classification by saccades

Eye movements are a behavioral response that can be involved in tasks as complicated as natural image classification. This report confirms that pro- and anti-saccades can be used by a volunteer to designate target (animal) or non-target images that were centered 16 degrees off the fixation point. With more than 86% correct responses, 11 participants responded to targets in 470 milliseconds on average, starting as quick as 245 milliseconds. Furthermore, tracking the gaze position is considered a powerful method in the studies of recognition as the saccade response times, ocular dynamics and the events around the response time can be calculated from the data sampled 240 times per second. The Hilbert transform is applied to obtain the analytic signal from the horizontal gaze position. Its amplitude and phase are used to describe differences between saccades that may testify to the recognition process.