Abstract
96 male rats were tested in open field in dim-light condition or bright-light condition for 3 min. per day for 5 days. The validity of 7 open-field test measures was assessed on the basis of the concept which was defined operationally using the test situation as the external criterion. Ambulation in the first 1 min. and rearing showed not only validity but also some generality. An interactive measure (ambulation in the first 1 min. and defecation) was proposed as a new significant measure. Larger intercorrelations among measures were obtained in a less stressful situation. In view of the results, an interpretation of previous conflicting results was proposed. Considerable constant factor-loading pattern across days and groups was noted, and this suggested the validity of the factor structure of an open-field test measure. Scores obtained on Day 1 showed some heterogeneity among scores obtained during 5 days.
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