Hemispheric specialization in visual, tactile and crossmodal assembling tasks.

There is ample evidence that the right or non-language related hemisphere of the brain is superior in processing of spatial information. This issue appears less clear when a task involves elaborate mental operations that require the integration of spatial information at a stage beyond mere perceptual discrimination. Examples are block design tasks, which are frequently used as estimates of general intelligence. Results of these tests have been contradictory as to whether there is a right hemispheric advantage for their execution. This study was aimed to look at a possible hemispheric preponderance in block design tasks comparing visual, tactile and crossmodal spatial performance. A two-dimensional template had to be reproduced by arranging cubes with surfaces different in both colour and texture. In the visual condition the template was given in the visual modality and the cube arrangement was under visual control. In the tactile condition the template was presented tactually and the cube assembly had to be done under entirely tactual control. In the crossmodal condition the template was presented visually and the assembly was restricted to tactual control. Task completion time (TCT) and number of correct responses (NCR) were compared between right hand and left hand responses. Only in the crossmodal condition a constant left hand superiority of performance was found. Non-crossmodal tasks did not show a constant hemispheric preponderance. In the tactile condition allowing for easy differentiation of input to one or the other hemisphere TCTs varied only according to the compatibility of side of afferent input and side of assembling action irrespective of the hemisphere engaged. It is concluded that mental operations requiring spatial assembling not necessarily engage the non-dominant hemisphere to a larger extent than the language dominant hemisphere. For crossmodal information processing, however, the non-dominant hemisphere appears to be superior.