Mirror-touch synaesthesia: the role of shared ... - UCL Discovery

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Chapter 3
discrimination of colour relative to non-synaesthetic subjects. They extend this by
showing:
i) synaesthetes who experience only touch show enhanced perceptual
discrimination of touch but not of colour,
ii) synaesthetes who experience both a tactile and visual concurrent show
enhanced perceptual processing of both touch and colour (although the
robustness of differences in colour processing was less strong than for tactile
processing),
iii) synaesthetes who experience only colour do not show enhanced sensory
processing in modalities outside of vision.
These findings suggest that enhanced perceptual processing is a core property
of synaesthesia, which is not limited to colour but occurs in each affected sensory
modality.
There are two possible accounts for why synaesthetes should demonstrate an
oversensitive concurrent perceptual system: 1) enhanced perceptual processing is a
consequence of the additional synaesthetic percepts which are experienced in
everyday life (i.e. enriched perceptual experience leads to enhanced perceptual
processing) or 2) enhanced perceptual processing is related to differences in brain
development as a function of synaesthesia (which may be either a cause or
consequence of synaesthesia; i.e. widespread differences in cortical connectivity or
mechanisms of cortical unmasking; Rouw and Scholte, 2007; Cohen Kadosh et al.,
2009).
Under the first account, an oversensitive concurrent perceptual system would
be explained as a proximal consequence of synaesthetic experience. For example, the
presence of stable synaesthetic associations may impact on the internal structure of