The parietal distance effect appears in both the congenitally blind and matched sighted controls in an acoustic number comparison task

Visual world experience is thought to play a significant role in the development of an abstract representation of quantity in the human brain. Nevertheless, some congenitally blind individuals demonstrate excellent numerical abilities. We show that blind adults have a phenomenologically normal semantic representation of number. Electro-encephalography data demonstrate that the numerical distance effect has similar parietal correlates both in the blind and in matched sighted controls. Our interpretation is that number comparison in the blind relies on a compensation network in the initial phase of number comparison. In a second phase, an evolutionarily hardwired parietal system is exploited. The representation of number meaning has both plastic and evolutionarily hardwired components. (c) 2005 Elsevier Ireland Ltd. All rights reserved.