Development of synaesthetic consistency: Repeated autonomous engagement with graphemes and colours leads to consistent associations

Abstract

Synaesthetic consistency is the hallmark of synaesthesia and plays an important role in the definition and validation of synaesthesia. It has been hypothesised that the acquisition of initially unspecified synaesthetic associations is based on consolidation processes. Thus, we investigated in non-synaesthetes whether repeatedly engaging with grapheme-colour associations mimics the developmental trajectory of synaesthetic consistency in genuine grapheme-colour synaesthesia. This was the case for the two tested experimental groups, irrespective of whether they were instructed to memorize their chosen associations, but not for the passive control group. Moreover, consolidated associations of the experimental groups resembled those frequently found in genuine synaesthesia. Furthermore, the acquisition of consistent graphemecolour associations resulted in a transfer of benefits to performance in recognition memory for abstract stimuli, as also found in genuine synaesthesia. Our findings suggest that consistent synaesthetic associations are based on consolidation processes due to repeated engagement with graphemes and colours.

Neurophenomenology of induced and natural synaesthesia

“…The associative nature of synaesthesia has led many to speculate that a learning component must be involved in the development of specific synaesthetic associations, especially when the inducers are cultural artefacts, as it is the case in grapheme-colour synaesthesia [5,6,10,43]. In line with this claim, the induced forms of synaesthesia reviewed here cast doubt on claims that genuine synaesthetic phenomenology can only occur in a rare subset of the population that exhibit a genetic predisposition [73,74].…”

“…For this reason, it will be interesting to investigate in future studies whether training-induced synaesthesia is associated with cognitive benefits found in natural synaesthesia, such as an enhanced memory (for a review, see [2]). A first training study, which examined if grapheme-colour associations are based on the consolidation of environmental contingencies, provides preliminary evidence that this may be the case [43].…”

“…[39]symbol-colourpost-hypnotic suggestionphenomenology, behaviourKusnir & Thut [40]letter-colourincidental learning (visual search)behaviourMeier & Rothen [30]letter-colourassociative learningbehaviour, psychophysiologyNair & Brang [9]sound-phosphenesensory deprivationphenomenology, behaviourNiccolai et al [41]grapheme-colourtraining battery (several tasks)behaviourNunn et al . [42]word-colourassociative learningbehaviourOvalle Fresa & Rothen [43]grapheme-colourincidental learning (generation of associations)behaviourRo et al . [44]sound-tactile sensationbrain injuryphenomenology, behaviour, neurophysiologyRothen et al .…”

“…In addition, all participants in the experimental group (18/18) also demonstrated letter-specific behavioural effects (e.g. consistency and synaesthetic Stroop) and phenomenology suggestive of natural synaesthesia (for similar effects on consistency, see [43]). Extending the previous study, these effects were found only for the experimental group—and not for either of the control groups.…”

Synesthetic Colors Associated with Personality

“…Studies with bilingual synesthetes revealed that synesthetic responses for the more recently obtained language depended upon similarity to the primary language (Mills et al, 2002, 2009; Mroczko et al, 2009; Rich et al, 2005; Witthoft & Winawer, 2006; also see Barnett et al, 2009 for review). Importantly, new grapheme-color associations can become highly consistent through repetition, even in adulthood (Ovalle-Fresa & Rothen, 2019). For example, Uno et al (2021) reported that as their adult subjects became increasingly familiar with rare Japanese characters over periods of 5 to 8 years, their grapheme-color synesthetic associations become more stable.…”