Previous experiments (1,3) on VTE 1 and visual discrimination learning in rats have indicated that the VTE starts to increase just before (or just as) learning begins, and after that it tends to decrease somewhat. VTE curves have not hitherto, however, ever been carried to a state of definite overlearning to see if, perhaps, when learning is complete, they may not then drop to a very low level.It has also been shown previously (3) that in initial learning rats do more VTE for an easy white-black discrimination than for a difficult white-grey discrimination. It has also been pointed out, however (4) that, in psychophysical experiments with human beings where the instruction as to the stimulus dimension to which they are to respond is already known, the more difficult discrimination tends to induce more rather than less VTE. As a possible explanation of this difference between rats and human beings it was suggested that whereas the data on VTE for rats has thus far been obtained only for the first part of learning (where essentially the animal is still learning what he is to pay attention to), the data for human beings in the psychophysical experiment are obtained after the instructions are already known. Therefore it appeared to us possible that, if rats were first brought to a condition of overlearning on an easy discrimination and then switched to a more difficult discrimination, they might, like human beings, do more rather than less VTE for the more difficult discrimination.The present experiment was an attempt, therefore, to investigate the following questions: (1) What, in general, is the course of the VTE curve for rats after learning has reached a stable maximum and overlearning has set in; (2) what will happen to VTE in rats when, after overlearning has been established on an easy discrimination, the animals are switched to a more difficult discrimination; and(3) how will the final level of VTE for rats on a relatively difficult discrimination compare with its final level on a previous easier discrimination?
THE EXPERIMENT
Differential personality changes for high-and low-aptitude groups were studied. Personality test and retest data were utilized from 5 different longitudinal studies; 3 studies were over a 2-yr. time period and 2 were over 4 yrs. Personality changes over 2 and 4 yrs. were studied for young adult males and females separately, 40 analyses of covariance were reported with retest means adjusted for initial test score. There was substantial evidence for: (a) young adults of higher aptitude to exhibit more personality change over time and in the direction of the trend of college students in general, and (b) young adults of higher aptitude to exhibit more "psychologically positive" personality development over time.
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