Introduction & Aims:
Social referencing is an important skill for infant exploration and social interaction (Klinnert, et al., 1983; 1986). We conducted a study to examine how infant characteristics affect emotional regulation during an adaptation of the visual cliff procedure.

Methods:
Two hundred fifty two mother-infant dyads were recruited for participation in the study and 41 participated in the newborn period. All infants were pre-term and healthy. The mean gestational age of the infants was 220.8 days (SD = 24.66). The majority of mother-child dyads represented middle-class, urban backgrounds.

Infant behavioral characteristics were rated using the Neonatal Behavioral Assessment Scale (NBAS). Heart rate variability (HRV) and EEG were measured once in the hospital and five times at home during the first six months after hospital discharge. HRV and EEG were recorded during the sleeping state. HRV total power represents sympathetic and parasympathetic nervous system function (Akselrod, et al., 1981). Right frontal EEG activity represents withdrawal-related behavior and left frontal activity indicates approach-related behavior (Davidson and Tomarken, 1989).

In the follow-up at 10 months, infants and their mothers participated in the adaptation of the visual cliff procedure. Emotional regulation was examined during the visual cliff procedure, with "crossing the visual cliff"- coded as representing better emotional regulation.

Maternal behavior was videotaped during home visits (for two hours each visit) and maternal responsiveness was rated according to Ainsworth's 9 points scale by four reliable raters (Inter-rater reliability between raters and the first author was .9). Raters were blind to each other's ratings and results of all infants' measures.

Non-parametric analyses (Mann-Whitney U test) were performed during statistical analysis of data.

Results:
Of the total sample of 41 infants observed at follow-up, 29 infants crossed the visual cliff and reached their mothers. Twelve infants did not. Those infants who demonstrated better emotional regulation by crossing the visual cliff showed higher performance scores on the NBAS during the first week after discharge compared to the infants who did not (p< .05). They also had higher scores of HRV total power during the first week after discharge compared to the infants who scored lower on the visual cliff procedure. (p<.01). The infants who crossed the visual cliff showed lower scores on right frontal EEG asymmetry (13.0~20.0Hz) before discharge (p<.05) and at six months after discharge (p<.05) than the infants who had lower scores on the visual cliff procedure.