Second language acquisition of American Sign Language influences co-speech gesture production

Previous work indicates that 1) adults with native sign language experience produce more manual co-speech gestures than monolingual non-signers, and 2) one year of ASL instruction increases gesture production in adults, but not enough to differentiate them from non-signers. To elucidate these effects, we asked early ASL-English bilinguals, fluent late second language (L2) signers (>= 10 years of experience signing), and monolingual non-signers to retell a story depicted in cartoon clips to a monolingual partner. Early and L2 signers produced manual gestures at higher rates compared to non-signers, particularly iconic gestures, and used a greater variety of handshapes. These results indicate susceptibility of the co-speech gesture system to modification by extensive sign language experience, regardless of the age of acquisition. L2 signers produced more ASL signs and more handshape varieties than early signers, suggesting less separation between the ASL lexicon and the co-speech gesture system for L2 signers.