Memory for an imagined pathway and strategy effects in sighted and in totally congenitally blind individuals.

The literature reports mixed results on the imagery abilities of the blind, at times showing a difference between sighted and blind individuals and at other times similarities. However, the possibility that the results are due to different strategies spontaneously used in performing the imagery tasks has never been systematically studied. A large group of 30 totally congenitally blind (TCB) individuals and a group of 30 sighted individuals matched for gender age and schooling were presented with a mental pathway task on a complex two-dimensional (5 x 5) matrix. After administering the task, participants were interviewed in order to establish the strategy they used. Results showed that both sighted and TCB may use a spatial mental imagery, a verbal or a mixed strategy in carrying out the task. Differences between the groups emerged only when last location and then entire pathway had to be remembered rather than just the last position, and were clearly affected by the type of strategy. Specifically, TCB performed more poorly than the sighted individuals when they used a spatial mental imagery strategy, whereas the two groups had a similar performance with a verbal strategy.