The effects of isolation rearing on exploration in the rat

The hypothesis that isolation rearing enhances exploration was tested in two settings which varied the extent to which exploratory behavior would be affected by competing hyperactivity. Experiment 1 measured exploration as contact of a discrete novel stimulus, in terms of bout frequency and duration. Locomotor activity was measured by photocell beam interruption. Isolation-reared rats were hyperactive, showed an increased incidence of exploratory bouts but no differences in duration of exploratory behavior, compared with group-reared controls. Experiment 2 measured, independently, locomotor activity and the preference for a novel environment over a familiar one. Isolation-reared rats, whether male or female, showed enhanced novelty preference compared with controls. No significant differences were found in locomotor activity. The results are discussed in terms of the hyperactivity of isolates interfering with investigative behavior by response incompatibility.     

Development of sex-trait stereotypes among young children in the United Staes, England, and Ireland

The Sex Stereotype Measure II (SSM II), a 32-item revision of the Williams, Bennett, and Best Sex Stereotype Measure, was developed to assess children's knowledge of conventional, sex-trait stereotypes defined by American university students. The procedure employed brief stories and human figure silhouettes which were individually administered to 5- and 8-year-old children in the United States, England, and Ireland and group administered to 11-year-olds in the United States. In the United States, knowledge of sex-trait stereotypes was found to develop in a linear fashion between the ages of 5 and 11, with more male traits than female traits being known at each age level. Cross-nationally, there was a high degree of similarity in the nature of the sex stereotypes being learned by the children in the 3 countries, although the rate of learning appeared slower among the Irish children. In all countries there was a clear progression in sex-stereotype learning from age 5 to age 8. English boys had greater knowledge of stereotypes than English girls, but this was not true in Ireland and the United States. Generally, knowledge of male stereotype traits appeared to develop earlier while knowledge of the female traits increased more rapidly between ages 5 and 8. The similarity in sex-stereotype learning in the 3 countries is discussed, and studies in progress in other countries of greater cultural diversity are noted.     

Social class, birth order, and newborn experience

Early home experiences of a group of 32 2-week old infants, equally divided according to social class, birth order, and sex, were studied. Naturalistic observations were taken on 2 consecutive days for a total of 6 hours. Compared with later-borns, firstborns received significantly more caretaker interaction on all variables studied. Compared with lower-SES infants, those from higher-SES homes received significantly more direct verbal interaction although the 2 groups did not differ on total periods of other types of caretaking interaction. The findings are consistent with birth order and social class differences reported in home environments of older infants and children.