When a lab mouse encounters an anesthetized cagemate, it doesn't just sniff and move on. It escalates through a stereotyped sequence: approach, sniff, groom, bite, and — in half of all cases — pull the unconscious mouse's tongue out of its mouth. The tongue-pulling isn't random agitation. It opens the airway and accelerates recovery from anesthesia.
The mechanism has been traced. Tongue stimulation activates glutamatergic neurons in the mesencephalic trigeminal nucleus, which project to noradrenergic neurons in the locus coeruleus — the brain's primary arousal center. The circuit is direct: tongue → brainstem → wakefulness. The rescue behavior works because a pre-existing neural pathway converts mechanical stimulation of the tongue into cortical arousal. The mice aren't performing medicine. They're triggering a reflex arc that happens to function as one.
Two independent systems converge. The prosocial behavior — driven by medial amygdala activation and oxytocin-expressing neurons in the hypothalamic paraventricular nucleus — produces tongue-pulling as a social response to an unresponsive companion. The tongue-brain arousal circuit — a sensorimotor pathway unrelated to social cognition — converts that pulling into physiological revival. Neither system was designed for the other. The social drive doesn't know about the airway; the arousal circuit doesn't know about the companion.
The behavior evolved because it works, but it works for reasons the behaving animal has no access to. The rescue is real. The intention to rescue is an attribution we project backward from the outcome. What the mouse experiences is social distress and a motor response. What the unconscious mouse experiences is waking up.