David Bryant (1992) argues for a common spatial representational system that operates on both verbal and perceptual input. To evaluate this possibility, a more detailed model will be needed, specifying at least (a) how the SRS works, (b) how and when it receives inputs, (c) how details of individual objects are incorporated into or associated with knowledge of their location, and (d) how the SRS interfaces with other, nonspatial knowledge. There are other details in which I'd be particularly interested as the argument for the SRS is further developed, including the degree of involvement of the SRS required in order to produce differential access.
1.2 Is there a single spatial representational system or format that integrates verbal and perceptual information about spatial configuration? Bryant argues for it, as have others (e.g., Jackendoff, 1987; Jackendoff & Landau, 1991; Miller & Johnson-Laird, 1976). Given that the end product of perceptual and linguistic input is the representation of a configuration consisting of details from both, and given phenomena such as the spatial interference effects of Easton & Bentzen (1987), the possibility of common representation, or at least shared resources, must certainly be considered. But to evaluate the possibility, it seems to me we'll need a more detailed model that specifies at least (a) how the SRS works, (b) how and when it receives input from perceptual and linguistic systems, (c) how details of individual objects are incorporated into or associated with knowledge of their location, and (d) how the SRS interfaces with other, nonspatial knowledge (so that, for example, indeterminate spatial relations can be encoded, or factual information about a landmark can be associated with knowledge of its location).
1.3 There are a few other details in which I'd be particularly interested as the argument for the SRS is further developed. In paragraph 2.8, Bryant argues that differential access is a feature of the SRS rather than of the perceptual or linguistic systems. Are we to assume from this wording that involvement of the SRS is REQUIRED in order to produce differential access? If so, is the SRS invoked on-line and from the beginning, during early processes of attention and learning? My guess, from Bryant's arguments and from previous research results (e.g., Logan, 1991), is that he would say yes.
1.4 Another aspect of Bryant's SRS that I'm curious to know more about concerns his arguments (paragraphs 3.3 & 3.4) for the use of absolute coordinate systems. First, is this restricted to absolute representation? It doesn't seem hard to find cases in which absolute positions of objects in allocentric or egocentric space are not known but relative positions are. (This would be more common for described than for perceived space.) But subjects can presumably form a spatial representation in such cases. Would Bryant argue that in these cases, subjects default to some arbitrary set of absolute coordinate values for the configuration and take a default perspective on it? Often, too, the distinction between absolute and relative representation becomes blurred, as in the case of egocentrically defined space, where the origin for the absolute scale is an arbitrary and mobile point.
1.5 There are, of course, many other details to be fleshed out, but these strike me as some of the basic ones. The arguments made by Bryant are timely and important, and the questions raised by his manuscript are worthy of pursuit. Here's hoping many more fruitful and funded years of research on spatial cognition can answer some of them.
Bryant, D.J. (1992) A Spatial Representation System in Humans. PSYCOLOQUY 3 (16) space.1
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