Is synaesthesia one condition or many? A large-scale analysis reveals subgroups.

Area of Science:

• Neuroscience
• Psychology
• Genetics

Background:

• Synaesthesia is a neural phenomenon where sensory stimuli trigger unintended perceptions.
• Dozens of synaesthesia forms exist, but their co-occurrence and relationships are poorly understood.
• Understanding synaesthesia co-occurrence may illuminate underlying neural mechanisms.

Purpose of the Study:

• To investigate which different forms of synaesthesia tend to co-occur.
• To identify potential groupings or clusters of synaesthesia types.
• To provide insights into the distinct underlying mechanisms of synaesthesia.

Main Methods:

• Analysis of synaesthesia form reports from 19,133 participants.
• Utilized correlation analysis, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and multidimensional scaling (MDS).

Main Results:

• Identified five distinct groupings of synaesthesia forms.
• These groups are: coloured sequence synaesthesias (CSSs), coloured music synaesthesias, non-visual sequela synaesthesias, spatial sequence synaesthesia (SSS), and coloured sensation synaesthesias.
• Findings indicate independent probabilities of expression for these synaesthesia groups.

Conclusions:

• Synaesthesia is an umbrella term for distinct groups of related phenomena.
• These groupings suggest potentially distinct underlying neural mechanisms.
• The findings open possibilities for different genetic bases underlying various synaesthesia types.