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Short-term memory for position and hemisphere advantage in hearing and deaf signers and nonsigners Allegra Cattani & J. Clibbens University of Plymouth, UK To investigate the visual short-term memory consequences of altered sensory and language input early in development, we studied visual memory for position in deaf signers and non-signers who had been auditorily deprived since birth and hearing signers and non-signers. The present work is the first attempt within the visuo-spatial cognition field to investigate a comparison study of a large sample (N=97) of four groups of participants involving deaf signers (N=28) and non-signers (N=18) versus hearing signers (N=20) and non-signers (N=31). In this way, we could compare the effects of deafness per se regardless of the effect of acoustic feedback and separately the effect of the presence/absence of acoustic feedback regardless of the effect of the signed and vocal language used. Although a decade ago only a handful of studies had attempted to systematically study the non-linguistic aspects of spatial cognition in deaf signers, recent studies involving mental imagery and motion perception and detection have investigated the brain reorganization documenting effects of sensory deprivation or sign language use. Results from studies with deaf signers (Neville & Bavelier, 2002; Bavelier, Brozinsky, Tomann, Mitchell, Neville & Liu, 2001; Bavelier, Tomann, Hutton, Mitchell, Corina, Liu, & Neville, 2000; Finney & Dobkins, 2001; Bosworth & Dobkins 1999; Neville & Lawson, 1987) suggested that visual perception in the deaf may be altered as a result of their auditory deprivation – this is the so called auditory deprivation hypothesis. Alternatively, altered visuo-spatial cognition in the deaf may arise as a result of their acquisition and use of sign language (Emmorey, Kosslyn and Bellugi, 1993, Emmorey and Bettger, 1995; Chamberlain and Mayberry, 1994) – this is the so called sign language hypothesis. In Study 1 we used a similar methodology to that of Neville & Bellugi (1978). The task was to determine whether a circle seen consecutively twice on a computer screen was placed in the same or a different position. Participants responded by pressing a key. In this way, no digit or letter was included in order to avoid any confounding effects with numerical or alphabetical processes. Furthermore, to analyze the lateralization effect we introduced a variant task where the circle was presented inside a grid of rectangles. In this way, the categorical (e.g., an equivalence class such as above, below, left of, right of) and coordinate (e.g., metric spatial properties) spatial relation representations (Kosslyn, 1987; Emmorey and Kosslyn, 1996) were also investigated. We believed that the grid condition may help participants as a “cue” (coded by vocal or signed language) to recall the location of the circle. Within the grid background condition the stimuli are categorized and identified by the participant in terms of the categorical spatial relation representation (for example in the task “identify the position of a circle in a grid” the participant can use as a strategy ‘the circle is in the upper left rectangle’ in - vocal or signed - language). Blank background stimuli are identified within a coordinate spatial relation representation (for example in the task “identify the position of a circle in a blank space” the participant does not use any vocal or sign description which can help him but uses only spatial cues such as near-far-same). Results showed that the use of sign language enhanced memory for position of a circle. The auditory deprivation hypothesis explained the relative enhancement. The deaf (regardless of sign language use) showed an atypical lateralisation compared to the hearing groups. The hearing showed a normal hemisphere advantage in terms of Kosslyn’s (1987) proposal of categorical spatial relation representations in the left hemisphere and coordinate spatial relation representations in the right hemisphere. By contrast, the deaf showed an atypical hemispheric