Comparison of blind and sighted participants' performance in a letter recognition working memory task.

The performance in letter recognition of 21 blind participants was compared with that of 16 age-matched sighted participants in an n-back working memory task. Blind participants were tested tactually with series of raised letters and Braille characters, and sighted participants tactually with series of raised letters and visually with series of letters presented on a computer screen. With this approach, we wanted to compare the tactual performances by trained (blind) and non-trained (sighted) participants, and tactual and visual performances by trained (blind and sighted, respectively) participants. Increments of mnemonic load increased the number of incorrect responses significantly in all n-back tasks. As expected, the blind participants outperformed the sighted ones statistically significantly in the tactile raised letters n-back task. The sighted participants produced significantly fewer incorrect responses in the visual task than the blind participants in the raised letters task, whereas there was no such difference between sighted subjects' visual performance and blind subjects' tactile performance in the Braille task. These results demonstrate the degree and limits to which everyday practice develops perceptual skills either in persons without sensory deficits (vision and visual environment), or persons with severe sensory loss (blindness and tactile environment). The performance level of blind persons relying on their tactile skills is just about the same as that of sighted subjects relying on their visual skills.