Education and Human Sciences, College of (CEHS)


Date of this Version



A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements Of the Degree of Doctor of Philosophy, Major: Psychological Studies in Education (Cognition, Learning, and Development); Under the Supervision of Professor Brigette O. Ryalls
Lincoln, Nebraska: November, 2009
Copyright (c) 2009 Regina T. Harbourne


As infants learn to sit between the ages of 5 and 8 months, they undergo many changes in their bodies as well as in their minds, creating conditions for the emergence of skills that allow greater interaction with their environment. The present study focused on the interaction of developing postural control in sitting with cognition, exemplifying the concept of the embodied mind. Look time, or the time an infant looks at an object, served as a proxy for the construct of cognitive processing. Three experiments examined developmental changes in sitting postural control and looking. The first experiment examined archival data of typical infants who were followed longitudinally as they learned to sit. Look time was found to decrease as sitting emerged. Postural control variables changed toward greater stability and regularity as sitting independence emerged. Using an age-held-constant design, infants at the age of 6 months who sat independently had significantly shorter look times when compared to their same-age peers who were not independent in sitting. Analysis showed that look time was consistently shorter for infants who had more postural stability at any sitting stage. Experiment 2 examined look time from archival data of infants with motor delay as sitting developed. Infants with delays exhibited the same changes in look time as the infants with typical development during sitting development. Lastly, a third experiment with typical infants beginning to sit found no difference in look time between the two conditions of unsupported sitting, and supported sitting, showing that simply being provided mechanical stability does not shorten look time. By exploring the interaction of maturation, postural control and look time, the present study reveals that sitting postural control interacts with looking in a way that drives cognitive change by expanding the infant’s ability to visually explore the environment. Developmental changes in look time are not simply due to maturation, but rather are due to interactions with experiences and movement opportunities.