You’re a cheeky 10-month-old, an expert crawler able to move with impressive speed on your hands and knees. The world is your oyster, so why do you bother staggering to your feet to become a doddering, novice walker?
Before now, psychologists looking for an answer to this question have been handicapped by the lack of observational data on how infants crawl and walk in a natural environment. When it comes to language development, there’s a long tradition of recording the words that infants are exposed to in real life, and the utterances they produce. But strangely, all the research on walking has been based on lab studies, getting toddlers to crawl or walk in a straight(-ish) path across a mat.
Now Karen Adolph and her colleagues at New York University have videoed 151 infants (aged 11 to 19 months) mucking about in a play room for an hour with their mum or other care-giver. The videos were coded to compare the movement patterns and fall rates of crawlers and walkers. The infants typically got mobile during brief bursts of activity – amounting to 32.3 per cent of the total time they were observed.
The data provide dramatic insight into the learning process involved in walking. In an hour, the average toddler took 2,368 steps (either walking or crawling), travelled 701 meters, and fell 17 times. Extrapolating to 6 hours (half a toddler’s typical waking day), this would translate to 14,000 steps a day, travelling the distance of 46 football fields, with 100 falls.
Comparing expert crawlers with novice walkers, the researchers made a particularly surprising discovery. After controlling for the fact the novice walkers spent more overall time being mobile than crawlers, the data showed that they didn’t in fact fall with any more frequency than the crawlers. This helps explain the mystery of why expert crawlers would give up a proven transport technique. “Part of the answer to ‘why walk?’,” the researchers said, “is ‘why not?’.”
Another useful outcome from the current research was that the researchers were able to compare the observational walking data from the play room with the infants’ performance on the classic standardised measure of walking (in a straight-line across a gait mat). The two correlated, providing for the first time evidence of the validity of the standard walking test.
“This corpus of natural locomotion indicates that infants accumulate massive amounts of … practice,” the researchers concluded. “They may be motivated to walk in the first place because walking takes them farther faster than crawling without increasing the risk of falling.”
Adolph, K., Cole, W., Komati, M., Garciaguirre, J., Badaly, D., Lingeman, J., Chan, G., and Sotsky, R. (2012). How Do You Learn to Walk? Thousands of Steps and Dozens of Falls per Day. Psychological Science, 23 (11), 1387-1394 DOI: 10.1177/0956797612446346