Old and new versions of the Molyneux question: A review of experimental answers

Abstract

The ‘Molyneux problem’ is typically framed in terms of the crossmodal matching of shape information from touch to vision. Indeed, shape along with intensity have commonly been considered amodal stimulus properties/dimensions (at least by developmental researchers). However, it is important to note that what is common, if anything, to the senses differs in the two cases: It is the physical stimulus (and possibly also the associated phenomenology) that is thought to be the same in the case of crossmodal (or intermodal) shape matching between touch and vision, whereas it is the nature of the underlying neural encoding that is said to be similar in the case of crossmodal matching of auditory and visual stimulus intensity. While the first empirical data to have been published on these two forms of putatively amodal crossmodal matching appeared to suggest that they both emerge surprisingly early in the course of human development (i.e., within the first month of life), certain of these seminal findings have proved difficult to replicate. Ultimately, therefore, there is currently little convincing evidence to support the notion that such putatively innate crossmodal matching of amodal stimulus dimensions is actually different in kind from the various other crossmodal correspondences that are seemingly acquired at various points during the course of human development (typically as a result of the internalization of the crossmodal statistics of the environment). As such, there may be nothing particularly special about the type of crossmodal matching thought to underlie the ‘Molyneux problem’, and continued interest in the issue may inadvertently have helped to sustain a misguided account of the differences between different types of crossmodal correspondence.