Investigations of the processing of brief visual displays, and the explanation of such processing in terms of iconic memory, are reviewed. It is concluded that the concept of a pre-categorical sensory memory for visual material remains tenable. The ability to report material from brief visual displays is seen as depending upon parallel (and perhaps unlimited) transfer from iconic memory to a post-categorical memory mode, followed by a limited (and perhaps serial) transfer to an output stage. Decisions about, or responses to, items can only be made when they are in the output stage. Because transfer out of the post-categorical mode can be performed on the basis of pre-categorical stimulus features, pre-categorical information about items in the post-categorical mode must be accessible. One way in which this would be possible is if the transfer of an item into the post-categorical mode takes the form of the creation, to represent the item, of a temporary file of information including both pre-categorical and post-categorical features of the item. Any such feature can be used as the basis for selecting the item for transfer from the post-categorical mode to the output stage, for subsequent decision or report.

Cues↗

PubMed1983

Surface dyslexia.

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Adolescent↗

PubMed1982

The psycholinguistic analysis of acquired dyslexias: some illustrations.

Three approaches to the neuropsychology of cognitive function are distinguished: the neuroanatomical (where the primary concern is to correlate particular disorders of cognitive function with particular lesion sites), the 'general-cognitive' (in which associations are sought between impairments of performance on specific cognitive tasks and general disorders of broadly defined cognitive processes) and the model-building (in which one attempts to interpret the pattern of impairments and preservations of some cognitive function produced by brain damage in terms of an explicit model of the normal operation of this function). I claim that the model-building approach to the neuropsychology of cognitive function must take precedence over the other two. One reason for this is that any disorder of cognitive function can only be defined with reference to some model of that function. I illustrate this claim with reference to acquired disorders of reading, describing current work of a psycholinguistic nature dealing with two acquired disorders of reading: phonological dyslexia and surface dyslexia. A psycholinguistic account of normal reading is used as a theoretical framework to define and to explain the patterns of deficit and preservation observed in these two dyslexias. The detailed account of surface dyslexia in English provided by this framework is then used to make predictions about the nature of surface dyslexia in other languages: alphabetically written languages where all words are regularly spelled, or where homophones cannot occur, as well as ideographically and syllabically written languages. A case of surface dyslexia in an English-Spanish bilingual, in which such predictions were confirmed, is described.

Adult↗

PubMed1980

The persistences of vision.

Human observers continue to experience a visual stimulus for some time after the offset that stimulus. The neural activity evoked by a visual stimulus continues for some time after its offset. The information extracted from a visual stimulus continues to be registered in a visual form of memory ('iconic memory') for some time after its offset. We may thus distinguish three distinct senses in which a visual stimulus may be said to persist after its physical offset: there is phenomenological persistence, neural persistence and informational persistence. Various assumptions have been made about the relation between these forms of visual persistence. The most frequent assumption is that they correspond simply to three different methods for studying a single entity. Detailed consideration of what is known about the properties of these three forms of persistence suggests, however, that this assumption is not correct. It can reasonably be proposed that visible persistence is the phenomenological correlate of neural persistence occurring at various stages of the visual system: photoreceptors, ganglion cells and the stereopsis system. Iconic memory on the other hand, does not correspond to visible persistence, nor to neural persistence in any stage of the visual system. Recent work, in fact, suggests that iconic memory is a property of some relatively late stage in the visual information-processing system, rather than being a peripheral sensory buffer store. This suggestion raises some fundamental theoretical issues concerning the psychology of visual perception, issues with which cognitive psychology has yet to come to grips.

Afterimage↗

PubMed1980