The unbounded productivity of (sign) language

Abstract

Abstract Unbounded productivity is a hallmark of linguistic competence. Here, we asked whether this capacity automatically applies to signs. Participants saw video-clips of novel signs in American Sign Language (ASL) produced by a signer whose body appeared in a monochromatic color, and they quickly identified the signs’ color. The critical manipulation compared reduplicative (αα) signs to non-reduplicative (αβ) controls. Past research has shown that reduplication is frequent in ASL, and frequent structures elicit stronger Stroop interference. If signers automatically generalize the reduplication function, then αα signs should elicit stronger color-naming interference. Results showed no effect of reduplication for signs whose base (α) consisted of native ASL features (possibly, due to the similarity of α items to color names). Remarkably, signers were highly sensitive to reduplication when the base (α) included novel features. These results demonstrate that signers can freely extend their linguistic knowledge to novel forms, and they do so automatically. Unbounded productivity thus defines all languages, irrespective of input modality.