An Experiment On Heredity Influence On Intelligence by Twin Study Method

Abstract

The twin study method is considered to be the most reliable one in order to study hereditary and environmental influences upon the development of intelligence.Six kinds of group intelligence tests were given to 543 MZ and 134 DZ twin pairs.The results obtained from these tests and their sub-tests told that MZ twins had higher degree of comformity than DZ twins.The evidence indicated heredity control for some functions that determined intelligence test scores,though some differences were seen in its power.The following subtests showed a strong heredity influence: 1.a test that required rapid mental activities 2.a test that involved verbal remembrance 3.a test that involved numbers and calculation 4.a test that involved recognition of the figure placed in various forms. On the other hand a test that had something to do with past experiences showed less strong heredity influence.These results might enable us to approach to the sub functions that constitute general intelligence. © 1968, The Japanese Association of Educational Psychology. All rights reserved.