The variability of innate darkness preference in mice: an evaluation of Ungar's design.

This study attempted to elucidate the controversy surrounding the experiments of Ungar examining the effects of scotophobin on dark preference in mice. The behavior of 45 noninjected mice in the type of maze described by Ungar was examined. Seven subsequent tests were conducted for dark box time (DBT) and motor activity. In general, the results indicated that DBT in all subpopulations of mice selected according to different criteria on the preference test fluctuated during the course of experimentation. Further, on the basis of the present data, the problem of summation effects from combined probabilities in the series of independent comparisons was readily apparent, so that the probability of obtaining significant differences between groups was increased as the results of Ungar's data analysis. A strong relationship between motor activity and DBT was also obtained, suggesting that other, nonspecific factors may influence motor activity and shorten the elevation of DBT.