Discourse Coherence in Agenesis of the Corpus Callosum: Latent Semantic Analysis of the Thematic Apperception Test

Individuals with agenesis of the corpus callosum (ACC) present with a cluster of cognitive, emotional, and behavioral symptoms that seem to stem from an underlying problem with complex cognition. Previous research with ACC has found these individuals to be deficient in their narrative descriptions of socially complex situations portrayed in pictures from the Thematic Apperception Test (TAT). Latent semantic analysis (LSA) was used to analyze TAT responses from individuals with ACC and normal controls in order to attain a measurable indicator of the discourse coherence of their responses. Individuals with ACC were hypothesized to have measurably less coherent responses than would normal controls, providing a marker of their difficulty with complex cognition. The responses of the ACC group were not significantly less coherent than those of the control group. Diminished discourse coherence in TAT responses, as measured by LSA, is thus not a symptom of ACC.