Social processing deficits in agenesis of the corpus callosum: narratives from the Thematic Apperception Test

Clinical observations suggest that individuals with agenesis of the corpus callosum (ACC) and normal IQ may have deficits in social intelligence. This study analyzed responses by normally intelligent individuals with ACC to pictures from the Thematic Apperception Test. A rating system was developed to assess three elements of story-generation: story logic, social understanding, and common content. Six individuals with ACC (five complete and one partial; IQs>85) were compared to eight controls matched for sex, age, and IQ. Based on independent rankings of story protocols by two raters, the five individuals with complete ACC were found to be significantly impaired on all three criteria. The one individual with partial ACC performed better than the majority of controls in all three domains. Results demonstrated that individuals with complete ACC are impaired in understanding socially complex scenes and generating appropriate narratives. Absence of the anterior corpus callosum appears to be important for this deficit.