Abstract In The World of the Newborn, Charles and Daphne Maurer (1988) proposed that the normal newborn is synesthetic. They argued that “the newborn does not keep sensations separate from one another, but rather “mixes sights, sounds, feelings, and smells into a sensual bouillabaisse” in which “sights have sounds, feelings have tastes,” and smells can make the baby feel dizzy (p. 51). In later publications, D. Maurer and Mondloch provided additional evidence for this hypothesis (Maurer, 1993; Maurer & Mondloch, 1996) and distinguished strong and weak forms of it (Maurer & Mondloch, 1996). The purpose of this chapter is to review the basis for the original hypothesis and to reevaluate it in light of the evidence since 1996 on the neural basis of synesthesia, on developmental plasticity, and on cross-modal interactions in nonsynesthetic adults and children.