[en] Recent studies suggest that patients with Williams syndrome (WS) present specific deficit in processing numerical magnitude (Krajcsi et al., 2009; O’Hearn & Landau, 2007; Paterson et al., 2006). Contradictory evidence has nevertheless been reported about a possible impairment of their subitizing abilities (Ansari et al., 2007; O’Hearn et al., 2005, 2011). As patients with WS were always tested in the visual modality, it remains unclear whether their deficit is specific to the processing of numerical magnitude or result from their basic visuo-spatial impairment (main characteristic of the WS cognitive phenotype). A first set of results supported the second hypothesis as people with WS were shown to have lower numerical acuity only in numerical tasks with high visuo-spatial processing requirements (i.e. comparing two lengths or two arrays of elements but not when comparing two durations or two sequences of flash in a single location; Rousselle & Noël, 2013). Recently, we tested whether a similar dissociation would be observed in processing the meaning of numerical symbols. Patients with WS were asked to compare the numerical magnitude of two Arabic numbers vs two spoken verbal numerals. They also had to enumerate sets of 1 to 7 dots shown for 250 ms to explore their subitizing abilities. Participants with WS were compared to two groups of children, one matched on verbal and the other matched on nonverbal mental abilities. Our results indicate that people with WS have difficulties in accessing the meaning of numerical symbols whatever the format and present smaller subitizing range.
