Testosterone and persistence in mice.

In view of previous studies showing that testosterone increases persistence of food searching in chicks, a single factorially-designed experiment was carried out to investigate whether a similar phenomenon occurs in male mice. Using a runway test, it was found that testosterone, injected into castrated mice, did increase persistence. It was also shown that intact males resembled more the testosterone-injected than control-injected castrates, and that females resembled neither intact males nor either group of castrates. A larger number of training trials was found to affect feeding latencies in a similar way to testosterone. Comparison of two strains differing in emotional reactivity (BALB/c and Porton) showed differences consistent with their reactivity levels.