Figure 1

The actograms show representative daily activity-rest patterns of toddlers of approximately 1.5 years of age with early nap onset times and long nap duration (a) and late nap onset times and short nap duration (b). The vertical axis shows the 7 consecutive observation days and the horizontal axis shows the course of each 24 h day from 9:00 h (9:00 am). Activity counts per minute are represented by the height of the vertical black bars on each actogram. The red arrows and the blue rectangles indicate naps and bathing periods, respectively. The red underlines are the periods that were automatically judged as sleep periods by the actigraph software. Note that the nap onset times are recognized as relatively early in (a) but as late in (b).