A novel, illustrated questionnaire to distinguish projector and associator synaesthetes

Individual differences in synaesthesic experiences have recently received much interest, with synaesthetes typically being classified as either projectors (seeing colours projected externally in space) or associators (experiencing colours in their "minds eye"). However, the current standard method of ascertaining these differences through self-reported ratings of statements has been found to be unreliable. Here, we report a test-retest comparison of two sequentially presented questionnaires, asking participants to rate how well the depictions reflect their own experiences. The first questionnaire used standard rating statements, while the second presented the synaesthetic experience in a visual, illustrated format. Results from 12 female synaesthetes highlighted the test-retest consistency with the illustrated questionnaire to be significantly higher than statements alone, suggesting that the visual presentation more approximates and reflects the synaesthetic experience. Through doing so, the illustrated questionnaire is considered to enable an accurate and reliable partition of synaesthetes into projectors and associators.