What Atypical Adults Can Teach Us about Development

In my presidential address, I described the early trap I fell into of describing the super‐baby capable of one after another adult perceptual ability, then how I discovered that two atypical populations of adults allowed me to study developmental mechanisms, namely, the role of early sensory input in sculpting the nervous system and the biological preparedness that constrains the experiential effects. Specifically, studies of adults who had dense central cataracts during childhood revealed that there are multiple critical periods during which visual input alters the potential of the nervous system for later refinement. Studies of adults with synesthesia generated novel hypotheses, subsequently supported experimentally, about the details of the biological preparedness that bias the child's early learning. Nevertheless, later studies indicated that considerable residual plasticity remains in adulthood.