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Abstract:
Some normal people "see" specific colors associated with
specific numbers or letters (graphemes). Is this a sensory effect
or simply a memory association? Are they simply being
"metaphorical" (just as we say cheese tastes "sharp")?
Synesthetically induced colors can lead to perceptual grouping and
pop-out, and are not seen with eccentric viewing, suggesting that
the effect is genuinely sensory (Ramachandran & Hubbard, Soc
Neurosci Abs, 30, 1222). Numbers or letters presented in the
periphery are difficult to identify if presented in the presence of
other, flanking, graphemes ("crowding"). This effect is attenuated
by presenting the target graphemes in a different color than the
flanking graphemes. We find that synesthetic subjects are
significantly better at identifying the target grapheme than
controls. Hence, synesthesia is a perceptual effect, as opposed to
a memory association, or mere "metaphor". Because synesthesia runs
in families, we propose that a single gene mutation causes
defective pruning between adjacent brain areas. (Hence the higher
incidence of synesthesia in artists and poets who may be more prone
to "metaphor"). Synesthesia might also provide a valuable
experimental lever for exploring the neural basis of metaphor.
(e.g., we say "disgusting" and make an expression when we smell
feces a process mediated by the ventromedial frontal. Is it a
coincidence that social and moral disgust use the same word and
expression, also involving ventromedial frontal)?
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