Date of Award


Degree Type


Degree Name

Doctor of Philosophy



Major Professor

Daniela Corbetta

Committee Members

Jennifer Bolden, Gordon Burghardt, Hillary Fouts, Jessica Hay


The acquisition of locomotor skills and transitions within them leads to changes in infants’ exploratory abilities and interactive behaviors, which affects several aspects of parent-infant exchanges. Here, we tracked how the onset of crawling and walking affected both infants’ and mothers’ spatial exploration, interactive behaviors, and use of postures in 10-minute free play sessions held in a laboratory setting. Thirteen infants and their mothers were followed longitudinally with biweekly sessions occurring from before crawling onset until infants had two months walking experience. We focused on two 6-session transition periods centered around the onsets of hands-and-knees crawling and walking. Behavioral data from the free play sessions were used to identify changes in spatial location coordinates, interactive behaviors, and postures within and across sessions. The use of location coordinates allowed us to derive measures of spatial exploration, including distance traveled, speed of travel, dispersion in the room, and distance between the mother and the infant. We related measures of spatial exploration to their interactive behaviors with toys, furniture and each other, their use of, and transitions between, postures, and the infants’ postural stabilization during play as they moved about the room. Results showed that predominantly with the acquisition of hands-and-knees crawling, infants increased their spatial exploration of the room, which was associated with concomitant increases in their interactive behaviors and postural changes. Mothers, on the other hand, showed an increase in spatial displacement in the room, but this increase was not associated with increased interactive behaviors or postural changes. This indicated that mothers’ spatial displacement was more likely driven by monitoring their child, and not active discovery of the room. As infants gained mobility, the distance between infant and mother increased. Mother-infant interactions and explorations therefore reorganized over time as infants gained motor skills.

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