Formation of automatic letter–colour associations in non-synaesthetes through likelihood manipulation of letter–colour pairings

Kusnir, F. and Thut, G. (2012) Formation of automatic letter–colour associations in non-synaesthetes through likelihood manipulation of letter–colour pairings. Neuropsychologia, 50(14), pp. 3641-3652. (doi: 10.1016/j.neuropsychologia.2012.09.032)

Abstract

Grapheme–colour synaesthesia is a well-characterized phenomenon in which achromatic letters and/or digits automatically and systematically trigger specific colour sensations. Models of its underlying mechanisms diverge on a central question: whether triggered sensations reflect (1) an overdeveloped capacity in normal cross-modal processing (i.e., sharing characteristics with the general population), or rather (2) qualitatively deviant processing (i.e., unique to a few individuals). To test to what extent synaesthesia-like (automatic) letter–colour associations may be learned by non-synaesthetes into adulthood, implied by (1), we developed a learning paradigm that aimed to implicitly train such associations via a visual search task that employed statistical probability learning of specific letter–colour pairs. In contrast to previous synaesthesia-training studies (Cohen Kadosh et al., 2009 and Meier and Rothen, 2009), here all participants were naïve as to the end-goal of the experiment (i.e., the formation of letter–colour associations), mimicking the learning conditions of acquired grapheme–colour synaesthesia (Hancock, 2006 and Witthoft and Winawer, 2006). In two experiments, we found evidence for significant binding of colours to letters by non-synaesthetes. These newly-formed associations showed synaesthesia-like characteristics, because they correlated in strength with performance on individual synaesthetic Stroop-tasks (experiment 1), and because interference between the learned (associated) colour and the real colour during letter processing depended on their relative positions in colour space (opponent vs. non-opponent colours, experiment 2) suggesting automatic formation on a perceptual rather than conceptual level, analogous to synaesthesia. Although not evoking conscious colour percepts, these learned, synaesthesia-like associations in non-synaesthetes support that common mechanisms may underlie letter–colour associations in synaesthetes and non-synaesthetes.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Thut, Professor Gregor
• Authors: Kusnir, F., and Thut, G.
• College/School: College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
• Journal Name: Neuropsychologia
• ISSN: 0028-3932
• Published Online: 25 September 2012