The human brain has the ability to categorize sensory input. This is called categorical perception (CP); it is how we make sense of the things we see, hear, and feel in our environments every day. One example of how we categorize the world around us is our perception of colors.  What constitutes the way we categorize the colors blue, red, green, yellow, brown, etc. is related to our culture and language.  Some languages have fewer color words than English, but it does not mean that the speakers of such languages cannot see the same colors as English speakers. Rather, their culture and language shapes and is shaped by the categories into which such colors are grouped.

One area that researchers are interested in understanding is how the human brain is able to categorize and discriminate between phonetic units.  Some researchers who have examined the categorization of speech sounds have supported two differing ideas.  The first is that CP of speech sounds is related to linguistic-specific processing; that is, a speaker’s experience with his or her native language shapes how sounds are categorized.  The second is that CP for language units is not learned, but is an innate part of our brain’s biology.  Previously, CP for language has been studied using spoken language only, but it has been difficult to understand the line between CP for general environmental sounds and CP for linguistic sounds.

By looking at ASL handshapes, Baker, Idsardi, Golinkoff, & Petitto (2005) examined these two ideas about CP.  If the processing of visual linguistic contrasts is a general perceptual ability, people who have had no experience with ASL should show CP for the handshapes in the same way as Deaf signers. On the other hand, if CP is language specific, only people who have been exposed to sign language should show CP for ASL handshapes. The signers and non-signers in this group were both able to identify the handshapes presented as being different from one another. However, only the signers exhibited CP for ASL handshapes. This study suggests that linguistic experience shapes CP for language.

The Perception of Handshapes in American Sign Language. (2005) Baker, S.A., Idsardi, W. J., Golinkoff, M., & Petitto, L.A.; Please see Petitto’s published papers and abstracts here.

Keywords: Modality, signed languages, handshapes, cognitive skills, linguistic units