Mechanical measurement of infant activity: a cautionary note.

Activity level in childhood has long been of interest to researchers in psychology, personality, and pediatrics. With the current epidemic in child obesity, even greater attention is being paid to physical activity and its role in preventing excess weight gain. Activity can be rated by observers as well as recorded more objectively by mechanical devices, however, some research suggests that estimates from these two sources do not always correlate. Via a demonstration with a human infant and a doll, the present report suggests that for younger infants at least, much of their measured activity may be confounded by their caregivers' movements.