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

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Chapter 1
to incongruent condition (Mills, Boteler, and Oliver, 1999), while non-synaesthetes do
not show this pattern. As with tests of consistency, this pattern of performance has
been found for different subtypes of synaesthesia, including not only grapheme-colour
synaesthesia, but also music-colour (Ward et al., 2006), music-taste (Beeli, Esslen,
and Jäncke, 2005), and mirror-touch (Banissy and Ward, 2007; summarised later in
Figure 1.5) variants.
Notably, individuals who have over-learned colour associations may also
behave similar to synaesthetes on the synaesthetic stroop task. For example, Elias and
colleagues report a single case study in which a non-synaesthetic individual with
reliable digit-colour associations, as a result of years of training using coloured
numerical codes in cross-stitching, performed comparably to synaesthetic subjects on
tests of consistency and stroop interference (synaesthetes differed from the control on
functional magnetic resonance imaging [fMRI] measures of synaesthesia in colour
selective regions but not on behavioural measures; Elias, Saucier, Hardie, and Sart,
2003). This is consistent with the findings of MacLeod and Dunbar (1988) who
trained non-synaesthetic subjects to associate black and white geometric shapes with
colour names over thousands of trials. When participants were later presented with a
stroop task, involving the geometric shapes presented in a congruent or incongruent
colour, the typical stroop interference pattern was observed (MacLeod and Dunbar,
1988). In neither study were subjects experiencing synaesthetic colour interactions,
implying that associative (rather than perceptual) components may be able to account
for some of the patterns of performance shown by colour synaesthetes on synaesthetic
stroop and consistency measures. However, more recent findings suggest that, in
colour synaesthetes, the synaesthetic stroop effect may be a consequence of both
perceptual and associative components (Nikolić, Lichti and Singer, 2007). Using