Twins : a study of heredity and environment / by Horatio H. Newman, Frank N. Freeman, Karl J. Holzinger.

  • Horatio Hackett Newman
Date:
[1937]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Twins : a study of heredity and environment / by Horatio H. Newman, Frank N. Freeman, Karl J. Holzinger. Source: Wellcome Collection.

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    16 TWINS: A STUDY OF HEREDITY AND ENVIRONMENT Hilgard, and one on the development of speech by Strayer.^^ A fourth study on attention by Thompson has been reported in abstract. The particular technique followed in these three studies is the same. It consists in giving one twin, designated T, a given type of training as soon as the infant appears to have advanced far enough in his development to profit by it, meanwhile withholding this special training from the other twin, then subsequently giving the same training to the second twin, designated C. The comparison, then, is between the effect of early training and de¬ ferred training. The plan of these studies does not make it possible to trace the later consequences of a contrast between the possession of a specific type of training and deprivation of that training. It bears chiefly on the question whether training is more effective at a later stage of maturation than at an earlier stage, and whether, consequently, maturation is an important factor in learning. It throws comparatively little light on the opposite question, whether learning is an important factor in development. The three studies are similar in their plan and in their conclusions. In the study by Gesell and Thompson, Twin T was given intensive training in climbing and in manipulation of cubes for six weeks, beginning at the forty- second week, when both twins were at the threshold of climbing and combining ability. Four days after the close of T's training С was given two weeks of training. Several weeks after the end of C's training T climbed with greater facihty and showed more confidence. However, a much shorter period of practice was needed to bring approximately the same facility at a later than at an earlier period. The same result was found in the case of manipulation of cubes. However, a well-marked difference in atti¬ tude appeared, in that С showed more dependency, caution or fearsome- ness. Hilgard trained the same twins according to the following schedule: initial test, eight weeks training of first twin, retest, eight weeks training of second twin, second, third, and fourth retests. The activities studied were digit memory, object memory, ring-toss, paper-cutting, and walking boards of various widths. The twins were approximately equal on the initial and final tests. The time at which practice was given, therefore, produced no difference in the ultimate skill. Early practice produced earlier proficiency, Josephine R. Hilgard, The Effect of Early and Delayed Practice on Memory and Motor Performances Studied by the Method of Co-twin Control {ibid., XIV, No. 6 [1933]), pp. 493-567. L. C. Strayer, Language and Growth: The Relative Efficacy of Early and Deferred Vocabulary Training Studied by the Method of Co-twin Control {ibid., WW, No. 3 [1930]), pp. 209-319.