The Visual Cliff
One of my favorite experiments in developmental psychology was the “visual cliff.” Researchers wanted to see if newly-crawling babies demonstrated depth perception. So they placed the babies on a table covered by a large sheet of plexiglass that extended far beyond the edge of the table. That way, when the babies came to the edge of the table, visually there would be a cliff, but the plexiglass would keep the babies from falling off. They then had the mothers call their babies, enticing them to crawl to the edge of the table and beyond. The question was, would the babies sense danger, turn around and go back, or would they just continue crawling past the edge of the table?
The results were remarkable. Four out of five babies (80%), even with their mothers calling them, stopped at the edge of the table, turned around, and crawled back. Pretty impressive. At least until the videotapes were reviewed. Upon further examination, it was found that of those babies that turned around, three out of four (75%), as they were turning around, actually placed their center of gravity over the edge of the table, so if the plexiglass wasn’t there, they would have fallen off the table.
This is why it is never wise to leave a baby unattended on a changing table or any other
high surface. If and when he gets to the edge, he may be smart enough to sense danger, but there is a good chance he won’t be smart enough to avoid it.