A developmental-genetic analysis of aggressive behavior in mice: I. Behavioral outcomes.

In Exp I, stable lines of mice that differed in the frequency and latency of attacks were rapidly established in 2 series (by S? in the 1st series and S? or S? in the 2nd). For evaluation of the developmental-genetic proposal, an analysis was made of the ontogeny of aggressive expression in male mice of the 2 series, with a report provided of the S? and S? generations of the 2nd breeding series (Exps II and III). Comparisons between results of a longitudinal design and results of a new type of cross-sectional design (involving only siblings, or co-sibial) indicated (a) a reliable developmental course of attack expression, with a sharp rise in early maturity and a slow decline thereafter; (b) a convergence in later maturity of the behavior of lines selectively bred for high or low aggressive behavior, if Ss had been assigned to the longitudinal design; (c) a strong effect of repeated testing on attack latency and frequency, even though the dyadic tests were brief in duration and separated by long intervals. In addition, cross-generational comparisons suggested that the selective breeding differences came about primarily by changes in the behavior of the low aggressive lines, in that these Ss failed to show in early maturity the sharp increases in attack occurrence that were observed in earlier generations. Implications for developmental and evolutionary concepts (e.g., neoteny, acceleration, and heterochrony) are discussed. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)