N. Masataka (1996) reported results of an experiment in which 6-month-old deaf infants were presented with videotapes that showed 5 identical scripts signed in Japanese Sign Language by 5 deaf mothers toward their deaf infants or toward their deaf friends. The experiment demonstrated that infants showed greater attentional and affective responsiveness to infant-directed signing than to adult-directed signing. The present study explored the possibility that this same phenomenon might extend to hearing infants who have never been exposed to signed language. When the same stimulus tape as used previously was presented to 45 six-month-old hearing infants, they too showed greater attentional and affective responsiveness to infant-directed sign than to adult-directed sign. This fact suggests that infants are prepared to detect sign motherese characteristics without specific experience in the modality.