Abstract

To study the cognitive mechanisms underlying backward counting we analyzed errors produced by a group of children with developmental dyslexia. Most errors involved decades which were omitted (31, __, 29), substituted (81, 70, 79) or anticipated (61, 60, 50, 59). We suggest that these errors reflect specific mechanisms operating in backward counting. Two control commands are assumed to operate within the phonological shortterm memory in order to suspend the number sequence and to allow the substitution of the decade number with the next one. A defective temporal activation of these control mechanisms produces errors that are limited to decades.