Theory of mind development in deaf children: a nonverbal test of false-belief understanding.

Our aim in this study was to investigate whether previous findings pointing to a delay in deaf children's theory of mind development are replicated when linguistic demands placed on the deaf child are minimized in a nonverbal version of standard false-belief tasks. Twenty-four prelingually deaf, orally trained children born of hearing parents were tested with both a verbal and a nonverbal version of a false-belief task. Neither the younger (range: 4 years 7 months-6 years 5 months) nor the older (range: 6 years 9 months-11 years 11 months) children of the final sample of 21 children performed above chance in the verbal task. The nonverbal task significantly facilitated performance in children of all ages. Despite this facilitation, we observed a developmental delay: only the older group performed significantly above chance in the nonverbal false-belief task, even though the younger children were at the average age when hearing children normally pass standard false-belief tests. We discuss these findings in light of the hypothesis that language development and conversational competence are crucial to the acquisition of a theory of mind.