ABSTRACT
It is also true that some babies naturally require a lot more sleep than others. Our figures certainly indicate very extensive individual differences in the sleep requirements of one-year-olds. From the complete distribution of sleeping times, we found that a few babies were reported as regularly taking as little as nine hours' sleep in the twenty-four, whereas, at the other extreme, one or two babies seemed to need as much as eighteen hours a day. The range of individual differences is thus so large that some babies appear to require literally twice as much sleep as others.
