Abstract
How does our ability to effortlessly move about the immediately visible environment – without running into the kitchen walls or banging into the table, for example – develop? One prominent, and intuitive, idea argues that “visually-guided navigation” develops early, when infants first begin moving independently through their surroundings via crawling. By contrast, some classic behavioral work as well as recent neuroimaging work has suggested that visually-guided navigation develops surprisingly late, not until children are “adult” walkers, around 8 years old. To directly test these hypotheses, using functional magnetic resonance imaging (fMRI) in children at 5 and 8 years of age, we measured the response in OPA – a brain region known to support visually-guided navigation in adults – to videos depicting the first-person visual experience of the two ways by which we move about the environment over development (i.e., a “crawling” perspective and a “walking” perspective), as well as two control conditions by which humans do not (i.e., a “flying” perspective and a “scrambled” perspective). We found that the OPA in 8-year-olds, like adults, responded more to the walking videos compared to the crawling, flying, and scrambled ones, and did respond any more to the crawling videos than to the flying or scramble ones, suggesting that OPA is adultlike by 8 years of age, and interestingly supports information from a walking perspective only. Surprisingly, the OPA in 5-year-olds showed a very different pattern, responding similarly across all videos, which indicates no “walking sensitivity”. Taken together, these findings i) reveal that the visually-guided navigation system undergoes protracted development, not even supporting walking in early childhood, and only emerges around 8 years of age, and ii) raise the intriguing possibility of whether crawling (and early walking) is a mode of visually-guided navigation at all, or is processed by a different neural system.