We welcome the Editors' invitation to reply to Dr. Gur's Perspective "Seeing on the Fly", in which he argues that visual perception is entirely driven by snapshot images resulting from saccade landings, and against the idea that vision is a dynamic process that incorporates information present in the temporal transients delivered by all kinds of eye movements. In Gur's opinion, saccade landings act as image "flashes" and elicit neural responses that dominate the entire periods of fixation, so that, contrary to recent findings, the small eye movements that continually occur during fixation serve no perceptual function.
Unfortunately, Gur's Perspective is affected by numerous flaws, including neglect of a large body of literature, misconceptions concerning proposed dynamic theories, inaccurate portrayals of eye movements and neural responses, arbitrary and unjustified assumptions on neural processing, erroneous interpretations and multiple factual errors concerning previous experimental findings and procedures. Practically every point raised against dynamic theories, and almost every point raised in favor of saccade landing acting as an instantaneous flash, contains inaccuracies and/or misplaced assumptions. Once these errors are recognized, Gur's proposal becomes baseless and illogical.
This letter aims to clarify the major misconceptions present in Gur's Perspective and correct the most glaring inaccuracies. In Gur's defense, we acknowledge that his perspective follows the traditional camera-like view of the visual system, the pervasive view based on explicit spatial processing and representations that match naive introspection. Since many readers may only be familiar with this textbook view, we briefly summarize the concepts of dynamical vision before addressing Gur's Perspective.
Recognizing that vision relies on the dynamic signals provided by all kinds of eye (and body) movements opens up important new areas for experimental and theoretical studies, including the extent to which eye movements can be tuned and controlled to improve performance, how these control signals are naturally generated, and how planning, oculomotor, and visual signals interact.