Date of Award


Degree Type


Degree Name

Doctor of Psychology (PsyD)

Committee Chair

Susan Tinsley Li


Increasing prevalence of twin births prompts the need for progress in our efforts to understand unique developmental characteristics of twins compared to singletons. When considering differences in twins’ and singletons’ cognitive, psychological, and social development, previous literature has demonstrated inconsistencies depending on the construct. Therefore, a global assumption that twins will differ from singletons in early development is refutable, and specific constructs must be examined individually. One consistency found in the literature is that early medical risk factors (e.g., prematurity, low birth weight) contribute to developmental differences found between twins and singletons. The purpose of this study was to examine differences between medically high-risk twins’ and singletons’ executive function and mastery motivation development during the first few years of life. Fourty twins and 40 singletons who participated in a Neonatal Intensive Care Unit (NICU) follow-up evaluation were matched for three risk variables: birth weight, gestational age, and number of days spent in the NICU. Existing clinical data, including demographic information and scores from the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley III) and the Dimensions of Mastery Questionnaire, 17 were analyzed. A chi-square test revealed no significant differences between twins’ and singletons’ executive function scores, as measured by object permanence items on the Bayley III. Results from an analysis of variance revealed differences between twins and singletons on the mastery motivation subscale of negative reaction to failure, and this finding approached significance at the adjusted p-value. No other group differences were found for mastery motivation subscales. This study serves as a catalyst for additional research into differences between twins’ and singletons’ executive function and mastery motivation development. Improved understanding of twins’ unique development will promote optimum clinical service delivery (e.g., developmental evaluations, early intervention, parent support, etc.), as well as better early childhood outcomes.