Extensive Phenomenological Overlap between Induced and Naturally-Occurring Synaesthetic Experiences
bioRxiv Preprint Server August 3, 2020 David. J. Schwartzman, Ales Oblak, Nicolas Rothen et al. 4 citations preprint
Grapheme-colour synaesthesia (GCS) involves automatic, consistent colour experiences triggered by letters or numbers. Two recent studies showed that extensive associative training can produce behavioural, neurophysiological, and phenomenological markers of synaesthesia in non-synaesthetes, but they did not deeply compare the induced experiences to natural synaesthesia. This study analyzed interview transcripts from participants who underwent such training and from natural synaesthetes. Both groups shared several experiential categories, including stability, location, shape, relative strength, and automaticity of colour experience. However, automaticity differed significantly: natural synaesthetes mostly reported automatic experiences, while induced synaesthesia-like experiences were mostly described as wilful. Additional categories emerged only in natural synaesthetes, highlighting heterogeneity. The results indicate that intensive training can alter conscious perception, producing phenomenology substantially resembling natural synaesthesia.