Comparing sign language and speech reveals a universal limit on short-term memory capacity

Short-term memory (STM) for signs in native signers consis-tently shows a smaller capacity than STM for words in native speakers (see Emmorey, 2002, for review). One explanation of this difference is based on the length effect: Short items yield higher spans than items that take longer to pronounce, pre-sumably because of limited processing time. Signs in American Sign Language (ASL) take longer to articulate than English words (Bellugi & Fischer, 1972). This is not problematic in natural language use, because ASL conveys information si-multaneously. However, with immediate serial recall, articula-tion time looms large. Some researchers have argued that articulation time is suffi-cient to account for the sign-speech difference in STM (Em-morey, 2002; Marschark & Mayer, 1998; Wilson, 2001; Wilson & Emmorey, 1997). If so, then STM capacity is, at its root