Coloured Letters and Numbers (CLaN): a reliable factor-analysis based synaesthesia questionnaire

Area of Science:

• Cognitive Neuroscience
• Psychology
• Neuroscience

Background:

• Synaesthesia is a complex perceptual phenomenon with significant individual variability.
• Existing research highlights the heterogeneity even within specific synaesthesia subtypes like grapheme-colour synaesthesia.
• A need exists for standardized tools to quantify these individual differences in synaesthesia research.

Purpose of the Study:

• To design and validate a reliable and comprehensive questionnaire for grapheme-colour synaesthesia.
• To capture the heterogeneity of grapheme-colour synaesthesia, including factors like localisation, automaticity, deliberate use, and longitudinal changes.

Main Methods:

• A large sample of 628 synaesthetes participated in the study.
• Factor analysis was employed to develop the Coloured Letters and Numbers (CLaN) questionnaire with 16 items across 4 factors.
• External validation was performed using established synaesthesia research tests, alongside assessments of test-retest reliability and construct validity.

Main Results:

• The Coloured Letters and Numbers (CLaN) questionnaire was successfully developed, comprising 16 items loading onto four distinct factors.
• The questionnaire demonstrated good test-retest reliability and robust construct validity, both internally and externally.
• The identified factors (localisation, automaticity/attention, deliberate use, longitudinal changes) effectively capture synaesthesia heterogeneity.

Conclusions:

• The CLaN questionnaire is a reliable and valid instrument for assessing grapheme-colour synaesthesia.
• This tool can effectively measure individual differences in synaesthesia, facilitating further research into performance measures.
• The CLaN questionnaire provides a valuable resource for generating new hypotheses and advancing synaesthesia research.