The distribution of attention during toy play was studied in 6-, 9- and 12-month-old infants. Heart rate and behavior measures of attention were collected as the infants interacted with objects. There was a large deceleration of heart rate at the beginning of behaviorally defined focused attention, but little heart rate change for looks that only had behaviorally defined casual attention. Heart-rate-defined sustained attention occurred more frequently at the transition from the first instance of casual attention within a look to focused attention and during the cycling between subsequent epochs of casual and focused attention. These results show that heart rate and behavioral measures of attention are closely related in young infants at the beginning and end of object interaction but are inconsistently related within a single look at an object.