A theory of visual stability across saccadic eye movements

Abstract

We identify two aspects of the problem of maintaining perceptual stability despite an observer's eye movements. The first, visual direction constancy, is the (egocentric) stability of apparent positions of objects in the visual world relative to the perceiver. The second, visual position constancy, is the (exocentric) stability of positions of objects relative to each other. We analyze the constancy of visual direction despite saccadic eye movements.Three information sources have been proposed to enable the visual system to achieve stability: the structure of the visual field, proprioceptive inflow, and a copy of neural efference or outflow to the extraocular muscles. None of these sources by itself provides adequate information to achieve visual direction constancy; present evidence indicates that all three are used.Our final question concerns how information processing operations result in a stable world. The three traditionally suggested means have been elimination, translation, or evaluation. All are rejected. From a review of the physiological and psychological evidence we conclude that no subtraction, compensation, or evaluation need take place. The problem for which these solutions were developed turns out to be a false one. We propose a “calibration” solution: correct spatiotopic positions are calculated anew for each fixation. Inflow, outflow, and retinal sources are used in this calculation: saccadic suppression of displacement bridges the errors between these sources and the actual extent of movement.

Effects of perceptual context on transsaccadic visual matching

“…In the present experiments, it has been shown that conceptionally this may be regarded as an extension of the calibration theory of Bridgeman et al (1994), enforced by the radial anisotropy of the visual field. Alternatively, it may be considered as a contextsensitive evaluation theory in the sense of MacKay (1973): the context is provided by the saccade target attended to immediately before the eyes start to move.…”

“…One of the most recent suggestions for solving the problem of visual stability in the context of saccadic eye movements is the calibration solution of Bridgeman et al (1994). Basic to their approach is that it regards retinotopic representations as sufficient to ensure visual stability.…”

Computational models of spatial updating in peri-saccadic perception

“…They suggest that most of the visual information before the saccade is discarded, and that a new representation of the visual world is generated from new incoming information after the saccade [73]. Only some information from the pre-saccadic image, particularly the position and properties of the saccade target, are encoded in trans-saccadic memory.…”

Transsaccadic memory of position and form

“…One compelling solution to this problem is that the visual system has the built-in assumption that the world as a whole does not change during an eye movement. A mechanism that becomes important here is saccadic suppression; indeed, it has been suggested that saccadic suppression 'bridges the errors' that remain due to the imperfect cancellation mechanism (Bridgeman et al, 1994). Therefore, let us next look at saccadic suppression.…”

“…Saccadic suppression of image displacement therefore seems to imply either that the required precise comparison is normally not performed, or that transsaccadic memory about the location of objects is not available to the visual system, or is very poor. Indeed, Bridgeman et al (1994) in their theoretical account of visual stability assumed that there is no need for transsaccadic memory of object positions, rather, the spatial positions are calculated anew after each saccade. This raises the question of the nature of transsaccadic memory, and of what and how much information is contained in this store.…”