Exploring within-task calibration in free-flowing manual sampling in 9-month-olds*

Change occurring across multiple timescales, from milliseconds to year-long periods, is inherent to any developmental process. Short-time behavioral fluctuations on the scale of minutes illustrate flexibility and calibration to the environmental context; however, relatively little is known about how such behavior unfolds in less controlled conditions. The current study investigates how infants’ manual object sampling movements change within a short, spontaneous, free-flowing play session in a laboratory setting. Nine-month-old infants participated in a free-flowing dyadic play session with their caregiver, where they were free to move and interact. The analysis focused on how the duration of a sampling episode with an interactive object (a button-press toy that elicited visual feedback) changed during the 5-minute-long task. A subset of infants (n = 51) engaged with the object in at least three separate 30-second windows. Their sampling episodes were categorized into these windows to assess changes in sampling duration over time. We predicted that infants would sample the object for shorter durations over time, reflecting within-task movement calibration to better match the object’s properties. However, contrary to our expectations, a linear mixed model indicated no significant differences in sampling duration, which was around 1 second across the three windows. These findings suggest that 9-month-old infants maintained a consistent sampling pattern throughout the task, with no major changes in duration. One possible interpretation is that brief, 1-second-long sampling episodes functioned as a behavioral attractor, guided by pre-existing movement strategies suited to the object’s properties. While more research is needed to fully understand how infants adapt their actions in real time, the current study is an initial step in examining within-task calibration in infants’ self-initiated manual sampling.