Gary Morgan
The origins of Theory of Mind development and delay in deaf children comes from early
language and communication experience.
Recent research has shown that typically developing infants as young as 13 months display
evidence of theory-of-mind (ToM) abilities in nonverbal tasks. However, the preconditions
for false belief attribution have not yet been documented. This study investigated the role
of language experience in children’s ability to track false beliefs using eye-tracking methods.
In the first study, we compared 16- to 26-months-old, either hearing or deaf, with hearing
parents. The children viewed a movie of a cat chasing a mouse in a true and false belief
situation. The results show that hearing children, but not deaf children, accurately predict
the behaviour of the characters with a false belief. The second study compared the mental
state language in conversations of hearing mothers with deaf and hearing infants. Signed
and spoken conversations were analyzed with respect to mental state categories. The
results showed that mothers of deaf infants used far less cognitive mental state language
than mothers of hearing infants.
These findings support the position that access to at least a minimum of mental state talk
contributes decisively to the expression of ToM reasoning. Previously widespread reports of
ToM deficits at 4-5 years of age in deaf children may originate in atypical early
conversational experience. The reason why input from hearing care-givers to deaf children
differs from input to hearing children is complex. Earlier work suggests delayed
comprehension and production of mental state language in deaf infants. It is possible that
care-givers react to this delay by reducing usage of such structures in talk to the children,
thus further affecting their development. Deaf children with good language skills may still be
at a disadvantage in ToM reasoning later in development because of this early missed
period of language exposure.