Why do sensitive periods exist?
Sensitive periods are increasingly well-understood at the neural-physiological level. However, we know little about the evolutionary selection pressures that produce sensitive periods. In this talk, I present a formal modeling approach to studying the evolution of sensitive periods. We can model development as a specialization process during which individuals incrementally adapt to local environmental conditions, while sampling imperfect cues to the environmental state. We first compute optimal developmental systems for a range of ecological conditions. Then we expose these systems to simulated experiences in order to obtain developmental trajectories and distributions of mature phenotypes. My talk highlights four main results. First, matching empirical findings, sensitive periods often result from experience or from a combination of age and experience, but rarely from age alone. Second, individual differences in the duration of sensitive periods emerge across ontogeny: individuals who sample more consistent cue sets lose their plasticity at faster rates. Third, consistency in individual differences gradually develops across ontogeny (i.e., ‘personality’ emerges). Fourth, individuals might perseverate along developmental trajectories despite accumulating evidence that an alternate trajectory more likely matches the ecology. We find that formal evolutionary modeling can illuminate the rise and fall of plasticity over the life course.