Short-term memory (STM), or the ability to hold information in mind for a few seconds, is thought to be limited in its capacity to about 7 ± 2 items. Notably, the average STM capacity when using American Sign Language (ASL) rather than English is only 5 ± 1 items. Here we show that, contrary to previous interpretations, this difference cannot be attributed to phonological factors, item duration or reduced memory abilities in deaf people. We also show that, despite this difference in STM span, hearing speakers and deaf ASL users have comparable working memory resources during language use, indicating similar abilities to maintain and manipulate linguistic information. The shorter STM span in ASL users therefore confirms the view that the spoken span of 7 ± 2 is an exception, probably owing to the reliance of speakers on auditory-based rather than visually based representations in linguistic STM, and calls for adjustments in the norms used with deaf individuals.Working memory refers to the capacity-limited ability to maintain and manipulate information relevant to an ongoing task. Over the years, a large number of studies have focused on the part of working memory dedicated to short-term maintenance of information, which is known as STM. As reports have documented a significant relationship between the size of the STM capacity for linguistic material and language abilities (for review, see refs. 1,2 ), much work has been conducted to uncover the mechanisms underlying the STM capacity limit. One of the most common measures of capacity limits in STM is the digit span task 3 , where subjects must repeat lists of digits in the same order as they are presented (i.e., forward serial recall). The number of digits to be recalled is progressively increased, and the STM span is defined as the longest sequence reported correctly. As noted in a seminal study in 1956 by Miller 4 , our ability to process information in such short-term memory tasks has a capacity limit of seven plus or minus two items. The 'magical number' of 7 ± 2 has been widely confirmed as the capacity limit in STM since this early work.However, the view that 7 ± 2 is the standard capacity of STM has been recently questioned. When non-nameable materials are used, the span of STM drops to four or five items 5 (for review, see ref. 6 ). It has been proposed that a STM span of 7 ± 2 is the exception rather than the rule. One hypothesis is that the exceptionally high STM span of 7 ± 2 is specific to linguistic material and derives from the ability of humans to chunk linguistic information 6 . An alternative possibility, however, is that the exceptionally high STM span of 7 ± 2 might be an effect of modality, arising from greater STM capacity for encoding serial information in auditory STM as compared to visual STM. In the present studies, we examined STM span in native users of ASL, which offers a unique opportunity to separate the contributions of language versus modality to STM capacity.

Capacity limits in linguistic short-term memory (STM) are typically measured with forward span tasks in which participants are asked to recall lists of words in the order presented. Using such tasks, native signers of American Sign Language (ASL) exhibit smaller spans than native speakers ([Boutla, M., Supalla, T., Newport, E. L., & Bavelier, D. (2004). Short-term memory span: Insights from sign language. Nature Neuroscience, 7(9), 997-1002]). Here, we test the hypothesis that this population difference reflects differences in the way speakers and signers maintain temporal order information in short-term memory. We show that native signers differ from speakers on measures of short-term memory that require maintenance of temporal order of the tested materials, but not on those in which temporal order is not required. In addition, we show that, in a recall task with free order, bilingual subjects are more likely to recall in temporal order when using English than ASL. We conclude that speakers and signers do share common short-term memory processes. However, whereas short-term memory for spoken English is predominantly organized in terms of temporal order, we argue that this dimension does not play as great a role in signers' short-term memory. Other factors that may affect STM processes in signers are discussed.

Short-term memory (STM), or the ability to hold verbal information in mind for a few seconds, is known to rely on the integrity of a frontoparietal network of areas. Here, we used functional magnetic resonance imaging to ask whether a similar network is engaged when verbal information is conveyed through a visuospatial language, American Sign Language, rather than speech. Deaf native signers and hearing native English speakers performed a verbal recall task, where they had to first encode a list of letters in memory, maintain it for a few seconds, and finally recall it in the order presented. The frontoparietal network described to mediate STM in speakers was also observed in signers, with its recruitment appearing independent of the modality of the language. This finding supports the view that signed and spoken STM rely on similar mechanisms. However, deaf signers and hearing speakers differentially engaged key structures of the frontoparietal network as the stages of STM unfold. In particular, deaf signers relied to a greater extent than hearing speakers on passive memory storage areas during encoding and maintenance, but on executive process areas during recall. This work opens new avenues for understanding similarities and differences in STM performance in signers and speakers.

Short-term memory (STM) is thought to be limited in capacity to about 7 AE 2 items for linguistic materials and 4 AE 1 items for visuospatial information (Baddeley & Logie, 1999; Cowan, 2001). Recently, we (Boutla, Supalla, Newport, & Bavelier, 2004) challenged this dichotomy between linguistic and visuospatial STM by showing that STM capacity in users of American Sign Language (ASL) is also limited to about 4 or 5 items.

Previous studies have demonstrated that early deafness causes enhancements in peripheral visual attention. Here, we ask if this cross-modal plasticity of visual attention is accompanied by an increase in the number of objects that can be grasped at once. In a first experiment using an enumeration task, Deaf adult native signers and hearing non-signers performed comparably, suggesting that deafness does not enhance the number of objects one can attend to simultaneously. In a second experiment using the Multiple Object Tracking task, Deaf adult native signers and hearing non-signers also performed comparably when required to monitor several, distinct, moving targets among moving distractors. The results of these experiments suggest that deafness does not significantly alter the ability to allocate attention to several objects at once. Thus, early deafness does not enhance all facets of visual attention, but rather its effects are quite specific.