In this study, development of young children's understandings of maske
d facial expression was examined from the, perspective of the developm
ent of ''theory of mind''. In Experiment 1, short stories in which one
character masks facial expressions to make another character have fal
se beliefs were presented to 3-, 4-, and 6-year-old. They were asked q
uestions to assess their judgements an various mental states (desire,
belief, and intention) of story characters. And, to assess children's
''representational theory of mind'', they performed a ''Smaties Task''
. The results showed that recognition of masked facial expression was
developed from 3 to 4 years. Scores on ''Smaties Task'' was also impro
ved duing the same period. An additional analysis showed that the majo
r determinant of to determine the understanding of masked facial expre
ssion was not the age but the possession of ''representational theory
of mind''. In Experiment 2 more sophisticated but similar type of proc
edures were presented to 3- and 4-year-old children. Results replicate
d the results in Experiment 1 and the understanding of the intention o
f characters was also Found to develop from 3 to 4 years.