This study aims to determine the combined effect of degree of brain injury and age on mastery behavior among infants. Specifically, it investigates whether degree of brain injury in infancy can predict later competence, or mastery motivation behavior at both 7 and 10 months of age. In this context, mastery motivation is defined as “persistence” or the percent of time spent engaging in persistent behavior. To test the hypothesis that there would be a significant interaction between age and brain injury on mastery scores, participants engaged in 12-15-minute toy play sessions at 7- and 10-months-old. Data was analyzed using a two-way mixed ANOVA. Although a statistically significant interaction between age and brain injury was not found, the results showed a small main effect in the direction hypothesized: more brain injury was associated with lower mastery motivation scores. Also found in the direction hypothesized was that on average, mastery motivation scores were higher at age 10 months than at age 7 months among infant participants. Lastly, there was a significant difference in mastery motivation scores found among the severe brain injury group, where scores were statistically significantly higher at 10 months old than 7 months old. These results suggest that brain injury may remain relatively stable throughout infancy, unless the brain injury is severe. In the case of severe brain injury, mastery behavior appears to show a natural incline, as there were no interventions used in this study. On this understanding, varying degrees of brain injury should be considered when investigating brain injury in infancy and its effects on mastery behavior
