On The Simpsons, Nelson frequently shows his scorn by unleashing his trademark “Ha, ha.” While Nelson’s laughs sound the same every time he snickers at Springfield residents, a new study has shown that even similar sounding laughs are very different. And the human brain easily distinguishes between the sound of someone enjoying a joke or mocking someone and someone being tickled.
Dirk Wildgruber and his colleagues from the University of Tuebingen in Germany asked 18 men to undergo a brain scan while listening to recordings of actors performing three different types of laughter—giggles elicited from tickling, joking, or taunting. In one test, the men listened to the guffaws and then assessed whether joking, tickling, or mocking caused the laughs. Most knew when someone was laughing with someone or at someone, but found it trickier to catch tickling laughter.
For the second experiment, the men counted the episodes of hooting by using the actor’s sigh as a sign that the laughter had ended. This gave Wildgruber a way to distinguish between the types of laughing. When subjects identified social laughter—giggling at jokes and during mockery—the blood flow in the brain looked similar, meaning the brain activated the same regions in both cases. Yet when the men heard ticklish laughter, the blood flow changed.
"Laughing at someone and laughing with someone leads to different social consequences," says Wildgruber. "Specific cerebral connectivity patterns during perception of these different types of laughter presumably reflect modulation of attentional mechanisms and processing resources.”
That’s a fancy way of saying social laughter activates areas of the brain that process complex social details. But tickling laughter triggers blood flow in regions that process auditory information, while the areas that decode social cues work less.