Effects of prior experience in raised line materials and prior visual experience in length estimations by blind people

The purpose of this research was to examine the role of expertise (as a result of previous training) in the use of raised line materials, and of visual experience by blind adults (congenitally, early and late blind), by means of tasks involving size estimation of common objects and length estimation. Results showed that, depending on the size of the objects, most participants were more successful in size estimations of common objects than in length estimations. They also showed an effect of visual experience in common object size estimation and an effect of expertise in length estimation. The results on length estimation suggested that, in this type of task, the advantage provided by prior expertise in raised line materials could surpass the one generally brought by the duration of visual experience. The findings suggest that blind people could improve their spatial mental imagery through being encouraged to use raised line materials.