No bridge too high: Infants decide whether to cross based on the probability of falling not the severity of the potential fall

Fourteen-month-old walkers and 11-month-old crawlers decided whether to cross wide and narrow bridges (2-60 cm) spanning a large (71-cm) or small (17-cm) drop-off to reach their caregivers who encouraged them from the far side of the bridge. An additional group of 14-month-olds walked over a "visual bridge" apparatus, designed to match an apparatus with a real bridge and drop-off. Here, the drop-off and bridge were only illusory. Bridge widths were presented with a psychophysical staircase procedure and each infant received ~40 trials. In each study, an experimenter rescued infants if they fell. In every study, infants' behavior was recorded from side, front, and overhead views, parents provided retrospective reports of infants' crawling, walking, and falling experience, and an experimenter measured infants' body dimensions. Additional pilot data include various age groups, drop-off heights, and procedures. Videos from a subset of infants were excluded for various reasons.