Routes to short-term memory indexing: Lessons from deaf native users of American Sign Language

Abstract

Models of working memory (WM) have been instrumental in understanding foundational cognitive processes and sources of individual differences. However, current models cannot conclusively explain the consistent group differences between deaf signers and hearing speakers on a number of short-term memory (STM) tasks. Here we take the perspective that these results are not due to a temporal order-processing deficit in deaf individuals, but rather reflect different biases in how different types of memory cues are used to do a given task. We further argue that the main driving force behind the shifts in relative biasing is a consequence of language modality (sign vs. speech) and the processing they afford, and not deafness, per se.

Second Language Working Memory Deficits and Plasticity in Hearing Bimodal Learners of Sign Language

“…Th e diff erences between hearing and deaf individuals in terms of decreased digit span as well as increased spatial working memory performance have also been demonstrated in nonnative learners of sign (Capirci, Catt ani, Rossini, & Volterra, 1998;Keehner & Gathercole, 2007). Furthermore, language modality has been shown to bias individuals towards the use of diff erential working memory subcomponents (Hirshorn et al, 2012). Second language learners who are learning another language within the same modality (e.g., EnglishSpanish learners) could show similar working memory capacities barring any quality issues.…”

“…Th e phonological loop is well conceptualized for spoken languages, but how does the phonological loop operate when processing visual languages? Several studies have outlined the working memory system in native deaf signers (Wilson & Emmorey, 1997a, b, 1998Boutla, Supalla, Newport, & Bavelier, 2004;Hall & Bavelier, 2010;Hirshorn, Fernandez, & Bavelier, 2012). Emmorey (1997a,b, and) demonstrated that native deaf signers show similar phonological eff ects (i.e., phonological similarity eff ect, word length effect, articulatory suppression eff ect) for sign language.…”

“…Native deaf ASL signers have signifi cantly lower digit spans (i.e., 5±1) than typical native hearing English speakers (i.e., 7±2). Th ese diff erences cannot be accounted for by speed of articulation or rehearsal (Boutla et al, 2004;Hall & Bavelier, 2010) or the diff erences in the number of phonological parameters in a given sign (Hirshorn et al, 2012). It is thought that experience with auditory language and its serial properties create the environment to induce bett er temporal/phonological working memory systems for hearing individuals (Conway, Pisoni, & Kronenberger, 2009).…”

“…Examining second language learners' performance allows for an investigation into diff erences in a working memory system that is already att uned to a specifi c code and indexing strategy. According to Hirshorn et al (2012), hearing speakers have a preference (i.e., relative bias) for using the phonological loop to process spoken languages, whereas deaf signers have a preference for the visuospatial sketchpad. Th ese biases arise out of the nature of the language modality itself.…”

“…As mentioned above, the visuospatial sketchpad integrates visual and spatial information into a single code. Th us, the diff erences in language modalities might infl uence the preference of deaf signers' use of the visuospatial sketchpad for spatiotemporal indexing and hearing speakers' use of the phonological loop for temporally ordered information (Hirshorn et al, 2012). Hirshorn et al posited that there is a bias in the use of a specifi c slave system (i.e., indexing strategy) during language processing and rehearsal.…”