Each hemisphere of two commissurotomy and two hemispherectomy patients was tested separately on the book form of Raven’s Standard Progressive Matrice test (RSPM) and on the book, board and tactile forms of Raven’s Coloured Progressive Matrices test (RCPM). The two patients who had undergone complete cerebral commissurotomy were tested unilaterally with the aid of a contact lens technique which permits free unilateral ocular scanning and visual guidance. The two other patients had undergone dominant (right) and non-dominant (left) hemispherectomy for post-infantile lesions and were tested in free vision. IQ estimates for the left hemispheres based on RSPM scores ranged from 74 to 103 (mean 87) and right hemisphere IQ estimates ranged from 74 to 93 (mean 83). Whereas a small and insignificant trend for left hemisphere dominance was observed on the RSPM, an insignificant trend of right hemisphere superiority appeared on the RCPM. The same trend of right hemisphere advantage had been observed on a tactile-visual modification of the RCPM (D. Zaidel and Sperry, 1973). Thus, the suggested laterality pattern seems to be modality nonspecific. In contrast to the small difference in lateral preference for each of the two tests as a whole, the individual problem sets in both tests yielded different laterality indices. Further, bigger laterality effects were observed on more difficult items. The right hemispheres also seemed more labile and less sensitive to item difficulty than either the corresponding left hemispheres or normal subjects with comparable scores. Instructions to use an overt trial-and-error solution method with the board form of the RCPM resulted in a change of strategy in both hemispheres. But only the left hemisphere of patient N.G., who did not have a ceiling effect, seemed to benefit from the opportunity for error correction to become superior on this version of the RCPM. The right hemisphere seems unable to utilize partial information as if its solution strategy is non-constructive. Neither the isolated nor the disconnected hemisphere has the dramatic focal deficits, such as unilateral neglect of space or dramatically reduced RPM scores, which often accompany unilateral cerebral insult. To the extent that RSPM measures general intelligence (“g”), our data suggest that “g” is bilaterally represented though in unequal amounts for different parts of the test. Thus, the data better support the primary abilities model of intelligence with localized and neurologically dissociable cerebral organization, than they support a hierarchical model incorporating a concept of “g” that enters into all intellectual functions and is homogeneously represented in the cerebral cortex. It is suggested that “g” may contain at least two independent factors, 9L and gR.
Programa de Estimulación Cerebral