Abstract
The motivations behind rodent helping behavior are unclear. We hypothesize that helping behavior is motivated by an affective state. To test this, we used a paradigm in which one rat can help another by releasing him from a restrainer. Rats were left untreated or received an injection of saline, midazolam (anxiolytic), or nadolol (peripherally acting sympatholytic). Midazolam but not nadolol or saline blocked helping. However, midazolam-treated rats opened the restrainer to access chocolate, showing that midazolam blocks helping through an effect on affect rather than through sedation or the like. To determine the role of HPA reactivity, we measured the corticosterone response to a trapped rat. Rats with the highest corticosterone responses evoked by a trapped rat did not develop consistent helping behavior. Together, these results demonstrate that rodent helping behavior is motivated by an affective state of anxiety and antagonized by physiological stress.