Critical periods in language, cognitive development, and massive online experiments
Only a few years ago, it was widely accepted that cognitive abilities develop during childhood and adolescence, with cognitive decline beginning at around 20 years old for fluid intelligence and in the 40s for crystalized intelligence. The obvious outlier was language learning, which appeared to begin its decline in early childhood. All these claims have been challenged by a recent flurry of studies — both from my lab and others. In particular, the ability to collect large-scale datasets has brought into sharp relief patterns in the data that were previously indiscernible. The fluid/crystalized intelligence distinction has broken down: at almost any age between 20 and 60, some abilities are still developing, some are at their peak, and some are in decline (Hartshorne & Germine, 2015). Most surprisingly, evidence suggests that the ability to learn syntax is preserved until around 18 (Hartshorne, Tenenbaum, & Pinker, 2018). This has upended our understanding of language learning and its relationship to the rest of cognitive development. In this talk, I review recent published findings, present some more recent unpublished findings, and try to point a path forwards. I also discuss the prospects for massive online experiments not just for understanding cognitive development, but for understanding cognition in general.