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. (shrink)

Three experiments investigated level of processing effects on a variety of direct and indirect memory tasks, in the context of a processing theory of dissociations. Subjects studied words in five encoding conditions and received one of ten memory tests. In Experiment 1, four tests previously classified as conceptual showed a robust LOP effect, as did a direct perceptual test of graphemic cued recall. An indirect perceptual word fragment completion test was unaffected by LOP. Experiment 2 showed that a new indirect (...) version of a graphemic cued test was not affected by LOP. In Experiment 3, guided by a generation/recognition model, we constructed three new direct tests in which subjects identified words that were graphemically, phonologically, or semantically similar to studied words. The three tests differed in their sensitivity to study conditions, but LOP had no effect in any case, despite the involvement of deliberate conscious recollection. Contemporary explanatory frameworks couched as dichotomies do not provide an adequate account of the results. It seems necessary instead to specify the types of information activated by each encoding condition, the types of information required by each test, and how encoding and retrieval processes are modified by task instructions. (shrink)

The sensorimotor account of perception is akin to Gibsonian direct realism. Both emphasize external properties of the world, challenging views based on the analysis of internal visual processing. To compare the role of distal and retinotopic parameters, distractor effect – an optomotor reaction of midbrain origin – is considered. Even in this case, permanence in the environment, not on the retina, explains the dynamics of habituation.

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Eye movements play a variety of roles in perception, cognition, and communication. The roles are revealed by the duration of fixations reflecting the quality of processing in the first line. We describe possible roles of eye fixations in different temporal diapasons. These forms of processing may be specific to sensorimotor coordinations. Any generalization to other domains should be cautious.

Despite its computational elegancy, Jackendoff's proposal to reconcile competing approaches by postulating a parallel architecture for phonological, syntactic, and semantic modules is disappointing. We argue that it is a pragmatic version of the leading module which Jackendoff would probably prefer, but which he does not explicitly acknowledge. This internal conflict leads to several shortcomings and even distortions of information presented in the book.

While sharing the author's interest in the development of an action-based framework for memory research, I think the present version is neither new nor particularly productive. More differentiation is needed to describe memory functioning in a variety of domains and on the many levels of activity regulation. Above all, Glenberg's proposals seem to contradict empirical data.