Spin him right round, baby, right round
Allen sent in this tidbit (and the post title inspired by the catchy 80s Dead or Alive tune), from What's Going on in There? : How the Brain and Mind Develop in the First Five Years of Life (Lise Eliot):
From the book:
"These researchers exposed babies, who ranged in age from three to thirteen months, to sixteen sessions of chair spinning: Four times a week for four weeks, the infants were seated on a researcher's lap and spun around ten times in a swivel chair, each spin followed by an abrupt stop. ... Not surprisingly, the babies loved this treatment. ... In addition to this "trained" group, there were two groups of control infants, one that received no treatment, and one that came in for the same sixteen sessions but only sat on the researcher's lap in the swivel chair; they did not get to spin.
"The results were striking. Compared with both control groups, the babies who were spun showed more advanced development of both their reflexes and their motor skills. The difference was particularly marked for motor skills like sitting, crawling, standing, and walking. In fact, the study included a set of three-month-old fraternal twins, of whom one received the training and the other did not. By the end of the study, when they were four months old, the twin who had experienced the vestibular stimulation had mastered head control and could even sit independently, while the unstimulated twin had only just begun to hold his head up."
Lots of other good stuff in there, though this stood out as a very low-effort, high-impact fun activity.