How can testosterone exposure early in life affect avoidance behavior in hamsters?

The premise that testosterone exposure early in life affects avoidance behavior in hamsters is accurate. Research indicates that female hamsters typically emerge from a box faster and are more active in new environments than males, suggesting they may be innately less nervous.1

When female hamsters are administered a small injection of testosterone on the second day of life, their adult behavior shifts to resemble that of male hamsters. Because this behavioral difference persists even after castration, it is believed that early exposure to androgens causes a permanent sexual differentiation of the nervous system, rather than being a result of hormone levels present during adulthood. This organizational effect demonstrates how early hormonal environments can fundamentally shape an animal's responsiveness to stimuli and subsequent avoidance tendencies.12