Non-Cooperation, In-Group Defending, and Excessive Non-Cooperation.

<p>(<b>A</b>). Under low personal vulnerability, oxytocin produces more non-cooperation than placebo when in-group vulnerability is high rather than low (range 0–5, displayed ±SE). (<b>B</b>). Compared to placebo, oxytocin enhances motivation to defend the in-group when in-group vulnerability is high rather than low (based on <i>N</i> = 72; range 1–7, displayed ±SE). (<b>C</b>). Excessive non-cooperation (i.e., own non-cooperation>expected out-group non-cooperation; range −5 to +5; displayed ±SE) emerges under high in-group vulnerability when individuals received oxytocin rather than placebo.