Specifically, it prompts men to respond to emotionally neutral social stimuli as if they were threatening. (bowdoin.edu)
After one social defeat, hamsters abandon all territorial aggression and become highly submissive, even towards a non-threatening social stimulus such as a caged hamster or a smaller, non-aggressive opponent. (cbn-atl.org)
Laughter in our own species, of course, is triggered by a range of social stimuli and occurs under a wide umbrella of emotions, not always positive. (scientificamerican.com)