Elsevier

Cortex

Volume 126, May 2020, Pages 134-140
Cortex

Research Report
Synaesthesia is linked to a distinctive and heritable cognitive profile

https://doi.org/10.1016/j.cortex.2020.01.002Get rights and content

Abstract

This study argues that there exists, in the general population, a distinctive profile of cognitive traits that predisposes people to develop synaesthesia (termed a ‘synaesthetic disposition’). This consists of more vivid mental imagery, better episodic memory, and greater attention-to-detail (amongst others things). Using a machine-learning classifier, we show that it is possible to distinguish synaesthetes from others using only standard cognitive and personality measures. Importantly, people with multiple forms of synaesthesia have a more distinctive profile (i.e., they can be more accurately classified). This suggests that whilst the presence/absence of synaesthesia is dichotomous, the underlying causal mechanisms are continuous. Moreover, we provide evidence that the cognitive profile constitutes a heritable endophenotype. Non-synaesthetic relatives of synaesthetes are cognitively similar to synaesthetes. This provides new insights into why synaesthesia might have evolved (i.e., it is possible to have the cognitive benefits of synaesthesia in the absence of the anomalous experiences). The notion of a synaesthetic disposition represents a novel, quantifiable individual difference in cognition/personality. This paves the way for determining if this is linked to a distinctive pattern of clinical vulnerabilities.

Section snippets

Method

We report how we determined our sample size, all data exclusions (if any), all inclusion/exclusion criteria, whether inclusion/exclusion criteria were established prior to data analysis, all manipulations, and all measures in the study.

Results

As a preliminary analysis, the individual test scores of the synaesthetes are compared against the controls (see Supplementary for full test breakdown). Significant differences were found for accuracy scores on the Embedded Figures Test (t(199) = 2.832, p = .005) and Memory test (t(199) = 2.928, p = .004), with synaesthetes scoring higher. Moreover, synaesthetes self-report greater mental imagery across all senses (t(199) = 3.553, p < .001), greater sensory sensitivity (t(199) = 5.838, p

Discussion

This is the first study to show that synaesthetes can be discriminated from non-synaesthetes based on brief standard measures of cognition and personality using machine-learning classification. The accuracy of classification was shown to depend on two initially hypothesised variables: the extensiveness of a person's synaesthesia (someone with more extreme synaesthesia has a more distinctive cognitive profile) and whether one is genetically related to someone with synaesthesia (non-synaesthetes

Open practices

The study in this article earned Open Materials and Open Data badges for transparent practices. Materials and data for the study are available at https://osf.io/xk893.

CRediT authorship contribution statement

Jamie Ward: Formal analysis, Writing - original draft. Gözde Filiz: Data curation.

Declaration of Competing Interest

The authors declare no conflicts of interest.

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