Based on four-month temperament group status, 278 infants were invited to continue participation, and, of these, 234 participated at nine months. There was no differential attrition based on temperament group. Infants who dropped out were not significantly different from those who remained in the study in terms of negative affect, positive affect, or motor activity.
Of the 234 infants who participated at nine months, 152 (65.8 %) were Caucasian; 31 were African American (13.4 %); 14 Hispanic (6.1 %); 5 Asian (2.2 %), and the remaining 32 children were of other or mixed ethnicity. Eighty-four percent of the children (n = 187) came from intact homes and roughly half of the children (n = 111) had siblings. Mothers averaged 32 years of age (SD = 5.3) and fathers averaged 34 years (SD = 6.1) at the time of the child’s birth.
Of the 234 infants who participated at nine months, 152 (65.8 %) were Caucasian; 31 were African American (13.4 %); 14 Hispanic (6.1 %); 5 Asian (2.2 %), and the remaining 32 children were of other or mixed ethnicity. Eighty-four percent of the children (n = 187) came from intact homes and roughly half of the children (n = 111) had siblings. Mothers averaged 32 years of age (SD = 5.3) and fathers averaged 34 years (SD = 6.1) at the time of the child’s birth.
