Is There a Normal Phase of Synaesthesia in Development?

Synaesthesia (one sense triggering another) has recently become amenable to scientific investigation. Recent findings are reviewed. Maurer's developmental theory of synaesthesia is then discussed. The theory states that all human neonates have synaesthesia, but that by about 4 months of age the senses have become modularized to the extent that we no longer have synaesthesia. Possible ways of testing this important theory are described, and the distinction between this account and cross-modal matching (Meltzoff) is clarified.