Show I Intelligence of Twins Compared b by Y Science Science- Physical Traits Studied The most fascinating phases of twin comparisons are to the majority major major- ity of us those having to do with intellectual traits writes D. D Cecil Rife in the Scientific American The relative importance of heredity and environment in mental up make-up has been for centuries and still is a topic sure to arouse a lively discussion discussion discussion discus discus- sion in most groups of civilized man man man- kind Have twin studies shed any light on this question Considerable research has been done in this field by numerous in in- in tors There are certain difficulties difficulties difficulties however which are not often encountered in the study of physical traits We Ve cannot be sure whether a given mental test measures only innate learning capacity or whether part of the responses are the result of education and training Then too the person tested may mayor or may not respond to the best of his ability There are certain tests such as the Simon-Binet Simon and its revisions which have been thoroughly studied by psychologists over a period of I years and have been shown to be fairly valid measures of general learning capacity Hundreds of twins reared together have been give givet general intelligence tests by various investigators The average pair intra-pair difference obtained obtained ob ob- obtained for identical twins is approximately approximately approximately five points in IQ I.Q. an insignificant insignificant insignificant I figure On the other hand fraternal twins show on an average pair intra differences of from ten to twelve points which is a significant significant significant cant difference The obvious conclusion conclusion conclusion sion from such results is that intelligence in intelligence in- in is to some degree at least dependent upon genetic make |