Whether it’s a friend jumping out from behind a bush or accidentally walking into a web of fake cobwebs, most of us will have fallen victim to a scare prank at some point. Now scientists have come up with a theory for why “jump scares” are so often followed by laughter – with insights for pranksters hoping to concoct Halloween tricks that tickle rather than terrify. A popular explanation for why certain jokes or situations provoke laughter is that humour is all about surprise: successful jokes tend to set up an expectation that is overturned by the punchline. “The problem with that theory is that we find all sorts of things funny that aren’t surprising, and there are lots of surprises that we don’t find funny,” said Marc Hye-Knudsen, a PhD fellow and humour researcher at Aarhus University in Denmark, who led the research. Another recent theory is that humour requires both a violation in our sense of how the world “ought” to be, and the almost simultaneous assessment that this breach is harmless or benign. Such violations can take many different forms, from the violations of linguistic norms in puns and wordplay, to the social norm violations of embarrassment humour. Hye-Knudsen and his colleagues suspect that something similar may explain why the initial shock of a jump scare is often quickly followed by laughter. To explore this, they examined evidence from various experimental and real-world situations, from toddlers’ experiences of peekaboo – a game that most initially find upsetting, until they learn that it is benign and it becomes hilarious – to a field study conducted at a haunted-house attraction, which found that guests smiled or laughed after jump scares three-quarters of the time. “Haunted house attractions and horror films both deliberately immerse audiences in their make-believe worlds to increase their general state of fear, which makes their startle responses to the jump scare bigger. But that startle also immediately pulls them out of that narrative world, so they can reappraise it as benign,” said Hye-Knudsen. The team also examined data from 100 online scare prank videos, finding that successful pranksters tended to intensify the stimulus their victims were exposed to – by, for example, targeting common phobias, which perhaps compensates for viewers’ psychological distance from these events. “Seeing a video of a complete stranger being the victim of a scare prank may not register as much of a violation, because you’re not socially close to them, so online pranksters must spice up their pranks to get a bigger response,” Hye-Knudsen said. The research was published in Evolutionary Psychology. Hye-Knudsen believes his findings could have implications for pranksters plotting Halloween scares this week. “The main lesson would be, know your audience and tailor your Halloween scares accordingly,” he said. “Don’t dress up like a serial killer and hide in your grandmother’s closet, but don’t just walk up to your friend and say: ‘boo’, either: you need to anticipate what level of scary is going to violate your target’s expectations, but they’re also going to be able to laugh at afterwards. “Also, when you laugh, invite them to laugh along with you, so that they don’t feel they’re being laughed at, and the situation really is benign.” Dr Coltan Scrivner, a behavioural scientist at Aarhus University’s recreational fear lab, who was not involved in the study, said its conclusions fitted with his own research on the psychology of scary play. This showed that fearful experiences such as haunted houses are only perceived as playful if the fear is at the right level. “Many people, including scare actors, think that more fear is always better for the person being scared. However, research suggests this is not the case. Instead, people seek out a sweet spot of fear, where fun is maximised,” Scrivner said. “This paper suggests that humour may be one tool a scare actor can use or promote, in order to help people achieve [that] sweet spot. “Just keep in mind that one scare doesn’t fit all,” he added. “Everyone’s sweet spot of fear is a little different.”