Subjects

Thirteen mother-infant pairs volunteered to participate in a longitudinal investigation on the development of infant communication. They were contacted by letter from birth announcements in the local newspaper. All had full-term births with no complications and all passed a six-month hearing test. Only middle-income mothers older than 21 years were included in the sample. Seven infants were male and six were female. Twelve of the dyads were Caucasian and one was African-American.

Procedure

Infants and mothers were videotaped weekly from age 4 to 52 weeks and then bi-weekly from 53 to 104 weeks. Here we report the findings from twelve observation sessions on each infant, six sessions prior to and six sessions following the acquisition of visually guided reaching (see below for definition and coding) for a total of 156 observation sessions. By design, the observed first instance of successful visually guided reach was designated as observation session number seven, and coding was done for six sessions prior and six following and including the session containing the first observed reach. The age range for the first observation session was 5–16 weeks, for the last session the range was 18–30 weeks. The age range for the onset of the first observed instance of successful reaching was 12–22 weeks (Mean = 16.3 weeks). [This mean age of onset of 4 months was earlier than the Bayley norm for reaching onset of 4.8 months, which we attribute to the facilitative effect of the social context].