Postural Sway Model

Adolph recalls a proposal by Campos and colleagues about fear of heights in infants (which mediates avoidance responses) are induced by near-falling experiences. Minor scrapes, tumbles, disturbance of equilibrium act as a positive reinforcement towards the cliff-avoidance responses. Another possible origin of the fear is a discrepancy in the usual locomotion experience and the novel perceptual input at the brink of a solid surface. Logically, infants should show avoidance responses when facing the edge of a surface. However, the posture of the infant affects the presence of cognitive comprehension that the body cannot be supported in empty space (falling consequences). The sway model proposes that for infants to stay balanced in their postures (sitting, crawling, cruising sideways along furniture, and walking) they must maintain permissible postural sway (the area where the baby's body will not fall over due to sufficient muscle strength and torque). Permissible postural sway is unique to each
The gap apparatus has adjustable length for different length (but equivalent gap sizes) testing. Infants are incentivized to span the gap with a toy tool operated by the experimenter. In both conditions (sitting and crawling) parents stood at the far side of the landing platform and help incentivize infants to retrieve the toys experimenters planted. Trials (lasted each 30s) were coded into successful (contacting the toy safely), failed (falling into the gap), and avoidance (no attempt to span the gap). To address the staircase procedure, failing and avoidance are categorized into a single failed attempt. The second experiment replicated the first with an alteration in the gap change logistics. The mechanized gap rules out the possibility of infants avoiding risky gaps due to a constant gap length. The second experiment successfully replicated all results from the first