Individual differences in the capacity limitations of visuospatial short-term memory: research on sighted and totally congenitally blind people.

The study of visuospatial imagery processes in totally congenitally blind people makes it possible to understand the specific contribution of visual experience for imagery processes. We argue that blind people may have visuospatial imagery processes, but they suffer from some capacity limitations. Similar, although smaller, limitations and individual differences may be found in sighted people. Visuospatial imagery capacity was explored by asking people to follow an imaginary pathway through either two- or three-dimensional matrices of different complexity. The blind appear to use specific visuospatial processes in this task (Experiments 2 and 3), but they have difficulty with three-dimensional matrices; sighted people have no such difficulty with three-dimensional matrices (Experiment 1). On the other hand, when a three-dimensional pattern exceeded sighted capacity, the blind and sighted showed similar patterns of errors. Subsequent analyses suggested that both visuospatial processes and verbal mediation were used.