Abstract The hypothesis that newborns’ perception is synesthetic holds up well in light of recent evidence on the neural basis of synesthesia, on developmental plasticity, and on cross-modal interactions in non-synesthetic adults and children. The starting point for this paper is our previous proposal that newborns’ perception is synesthetic: that their undifferentiated sensory pathways lead to cross-modal influences on their perception resulting in perceptual experiences that resemble, in some respects, the perception of adults with synesthesia (Maurer 1993; Maurer and Maurer 1988; Maurer and Mondloch 1996, 2004; see Johnson and Vecera 1996, for a similar argument they called the parcellation conjecture).