The use of psychological state words during mother-child play sessions at age 3 was examined in 31 children diagnosed with delayed expressive language at 24-31 months and 21 age-matched typically developing comparison children. Children and mothers in the late talker group made more references to physiological states and fewer references to cognitive states than the children and mothers in the typically developing comparison group. The children's use of cognitive terms correlated significantly with measures of language ability, including mean length of utterance, Index of Productive Syntax score, and use of propositional complements, as well as with their mothers' use of cognitive terms. The delay in the emergence of psychological state words, particularly cognitive terms such as think and know, may affect other aspects of late talkers' cognitive and social development.
© 2002 by Cambridge University Press. Available on publisher's site at http://journals.cambridge.org/abstract_S014271640200406X.
Lee, Eliza C., and Leslie Rescorla. "The Use of Psychological State Terms by Late Talkers at Age 3." Applied Psycholinguistics 23 (2002): 623-641, doi:10.1017/S014271640200406X.