Being low mouse on the totem pole is tough on murine self-esteem. It turns out it has measurable effects on brain chemistry, too, according to recent experiments. Researchers found that mice that were bullied persistently by dominant males grew unusually nervous around new company, and that the change in behavior was accompanied by heightened sensitivity to vasopressin, a hormone involved in a variety of social behaviors. The findings suggest how bullying could contribute to long-term social anxiety at the molecular level.