Representing shape in sight and touch

Abstract

We represent shape in both sight and touch, but how do these abilities relate to one another? This issue has been discussed in the context of Molyneux's question of whether someone born blind could, upon being granted sight, identify shapes visually. Some have suggested that we might look to real-world cases of sight restoration to illuminate the relation between visual and tactual shape representations. Here I argue that newly sighted perceivers should not be relied on in this way because they are unlikely to form the kinds of shape representations responsible for cross-modal recognition in normally sighted perceivers. I then argue that the available evidence makes a compelling case for the type identity view, on which the visual and tactual representations responsible for cross-modal recognition are type-identical.

Spatial representations in sensory modalities

“…“ Quaere , whether by his sight, before he touched them, he could now distinguish, and tell, which is the Globe, which the Cube” (Locke, 1694/1975, book II, ch. IX, section 8) (Green, 2021b, p. 2)?’ This question has generated many significant discussions, and here I shall not summarise those controversies. I will instead follow Green's lead and see how the tactile field hypothesis is understood in this context.…”

“…If so, the ability to apply shape concepts on the basis of both modalities relies on learned or hardwired connections between these representations. (Green, 2021b, p. 2; emphasis added)And according to Green, there are three obvious possibilities of appealing to the idea of an intrinsic similarity between visual and tactile spatial representations. The first is the view he is recommending, called the ‘type identity view’, according to which ‘vision and touch generate tokens of the same representation type’ (p. 3).…”

“…The first is the view he is recommending, called the ‘type identity view’, according to which ‘vision and touch generate tokens of the same representation type’ (p. 3). The second is called the ‘rational link view’ (Evans, 1985), according to which ‘vision and touch generate distinct representation types that are … rationally linked’ (Green, 2021a, 2021b, p. 3). And finally, the ‘structural correspondence view’ has it that ‘vision and touch generate distinct representation types that, while not rationally linked, exhibit a structural correspondence that enables the subject to make reasonable inferences about whether seen and felt shapes are the same [Cheng, 2019, 2020; Leibniz, 1765/1981]’ (Green, 2021b, p. 3).…”

“…The second is called the ‘rational link view’ (Evans, 1985), according to which ‘vision and touch generate distinct representation types that are … rationally linked’ (Green, 2021a, 2021b, p. 3). And finally, the ‘structural correspondence view’ has it that ‘vision and touch generate distinct representation types that, while not rationally linked, exhibit a structural correspondence that enables the subject to make reasonable inferences about whether seen and felt shapes are the same [Cheng, 2019, 2020; Leibniz, 1765/1981]’ (Green, 2021b, p. 3). The tactile field hypothesis is rightly classified in this category because it holds that the visual field and the tactile field share some significant spatial structural similarities , contra Strawson (1959), O'Shaughnessy (1989), Martin (1992) and Soteriou (2013).…”

“…If so, the ability to apply shape concepts on the basis of both modalities relies on learned or hardwired connections between these representations. (Green, 2021b, p. 2; emphasis added)…”