Psychology Professor Jennie Pyers was featured in the November issue of “Scientific American Mind” for her current research on the theory of mind and language proficiency. Using deaf Nicaraguan Sign Language (NSL) learners as subjects, Pyers and her colleague Dr. Ann Senghas, Assistant Professor of Psychology at Barnard College, investigated how awareness of verbs such as “think” and “know” impact signers’ perceptions of situations.
The two Smith graduates experimented with groups of NSL users with varying levels of language proficiency, administering a “false-belief” test consisting of a visual story shown to signers. Two pictures depicted a series of events: a boy would stow a toy in one place and exit the room. Afterward, another boy would enter the room and hide that toy in a different location. Signers then had to indicate by choosing between two different pictures whether the first boy would seek the toy in the original spot or the new one.
Pyers and Senghas found that NSL users whose vocabularies were more advanced and contained mental state verbs were much more likely to correctly perceive “false-belief,” selecting the first alternative. Signers who did not originally succeed in identifying false-belief back in previous tests in 2001 often gained false-belief understanding after learning the necessary verbs. While it was possible for signers who had the verbs to misperceive the boy’s false-belief, “nobody had acquired…false-belief understanding and not the language,” Senghas said. Thus she and Pyers proved that linguistic ability to express false-belief is necessary for the perception of it.
Pyers and Senghas, who were introduced by their advisor at Smith College, thought up the experiment after seeing children’s reactions to a cartoon that involved the ideas of mental verbs. Pyers noted that the NSL speakers never spontaneously produced mental verbs in their retelling of the story. Now they know that those who did not have the mental verbs could not relate the idea of knowledge because they could not comprehend it.
While the false-belief understanding gap between hearing speakers and deaf signers has always been apparent (the age of acquisition is four years for normal children, 7 to10 years for the deaf), the development of NSL provided an unusual opportunity
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