Visual imagery without visual experience: evidence from congenitally totally blind people.

We explored the ability of congenitally totally blind people (who were contrasted with age-, sex- and education matched blindfolded sighted subjects) to perform tasks which are mediated by visual mental imagery in sighted people. In the first (pictorial) task, subjects had to mentally compare the shape of the outline of three named objects and to indicate the odd-one-out. In the second (spatial) task the participants were asked to memorise the position of a target cube in two- and three-dimensional matrices, based on a sequence of spatially based imagery operations. In addition, during half of the trials of both imagery tasks subjects were required to perform a concurrent finger tapping task, to investigate whether the blind subjects would be more dependent on spatial processing. Although blind participants made significantly more errors than sighted participants, they were well able to perform the spatial imagery task as well as the pictorial imagery task. Interference from the concurrent tapping task affected both groups to the same extent. Our results shed new light on the question whether early visual experience is necessary for performance on visual imagery tasks, and strongly suggest that vision and haptics may share common representations.