Animal laughter has been a controversial claim. Until fairly recently, laughter was considered uniquely human. However, most human behaviours have evolved and so we should not be too surprised to find primitive versions in other species. As many pet owners already know, their animals display behaviour that looks like they are having fun during rough and tumble play. Puppies and kittens seem to engage in behaviour that has no obvious rewards other than the joy of play. Initially it was argued that these behaviours were precursors to adult aggression – a means of developing survival skills for hunting. Even the interpretation of animal behaviour was misguided. For example, chimpanzees who bare their teeth in a smile are generally regarded as displaying a threat or fear response.
However, animal laughter during play had to be rethought when Jaak Panksepp made an amazing discovery with rats.25 First, he noticed that rats that had been deafened for experiments on hearing did not engage in as much rough-and-tumble play as normal rats. There was something missing in these deaf rats. It turns out that it was the squeals of delight. When Panksepp placed a sensitive microphone in the cage that makes high-frequency sound audible to human hearing, they discovered a cacophony of 50 kHz chirping during the play sessions – the rat equivalent of laughing. He soon discovered that rats were also ticklish and would chase the experimenter’s hand until they were tickled. Apparently, rats are most ticklish at the nape of the neck. They would play chase with the hand and all the other familiar baby tickling games like ‘coochie-coo’. Baby pup rats laughed the most, and as the play activity declined with age so did the laughing.
What is it about tickling that is so enjoyable? There is a tactile element to it, but that is not enough to explain the behaviour because it is well known that you cannot tickle your self.26 There is something about being tickled by someone else that is necessary to induce the experience. It turns out that it is the absence of self-control that creates the pleasure of tickling. Whenever we touch ourselves, our brains keep track of our movements. We need this self-monitoring in order to guide our movements but also to know whether changes in sensations are due to our own actions or changes in the external world. We are not aroused when tickling ourselves because the action is totally under our own control and predictable. However, researchers at the Institute of Neurology in London found that you could tickle your self with a tickling machine when there was a delay inserted between the action of operating the lever and the probe that did the tickling.27 When the self no longer seems in control, we surrender to the illusion of an external agent. This also explains why schizophrenic patients can tickle themselves because their self-monitoring is believed to be disrupted and they attribute sensations and experiences generated by their own brains and bodies as coming from somewhere else.28 No doubt losing this sense of self during tactile stimulation extends beyond tickling into other areas of sensual pleasure, which is one reason why getting a massage can be so enjoyable!
Laughter has been considered one of the primitive universal emotions recognized in every culture. Of all the different emotional expressions, laughter is one of the few that adults who have been deaf and blind from birth can generate, indicating that it predates other emotions in our evolution. If it is so old and shared with other species, this suggests that it may have a really important function. Although we all have moments of solitary mirth, private jokes that make us smile, laughter is predominantly a social phenomenon that has its roots both early in human development and also early in the development of our species.
We like to laugh and make others laugh. Not only does laughter have a multitude of benefits in terms of coping with stress and illness, but it works to bind individuals together in social coalitions. It is a deep emotional response activated by the emotional regions of the amygdala and associated brain networks, but it operates in conjunction with higher order processes related to social cognition – thinking about others. We use laughter to signal our willingness to be members of the group and we also laugh at others to ostracize them. In this way, laughter is a powerful weapon of group coalition and identity. However, sometimes this weapon can go off on its own. We know this because various disorders that disrupt the connectivity of the different brain regions associated with laughter can lead to impulsive and socially inappropriate outbursts.29 Multiple sclerosis, strokes, Alzheimer’s disease, Parkinson’s disease and other forms of brain lesions can damage the communications between different parts of the brain that control social behaviour. Even in healthy adults, the stress of highly emotional situations such as funerals can cause us momentarily to lose the capacity to suppress our giggling. It’s also one of the reasons that alcohol and comedy go hand in hand. When you drink you are partially disinhibited because alcohol impairs cortical suppression. We are more at ease and less concerned about our behaviour in public. We become louder, sillier and find jokes funnier, or at least laughing at them more acceptable. Socially appropriate laughter requires not only interpreting complex social situations but also regulating impulses that may be inadvertently triggered. This is why children must learn to control laughter. We may be born to smile and laugh, but eventually our cultures take over and tell us when it is appropriate to do so. This may explain why comedians are continually pushing the boundaries of socially acceptable humour and yet deep down we are egging them on. We take delight in testing the boundaries of our own self-control.
Securely Attached to Apron Strings
Initially most babies are party animals – staying up all night and willing to be friendly with anyone. They find all adults fascinating. It may be true that in comparison to other women, young babies prefer to look at their own mother’s face, listen to her voice and prefer the taste of her breast milk as well as her smell,30 but when it comes to socializing, young babies initially don’t care who the adult is so long as they interact with them in a meaningful way. Meaningful for a young baby means attentively. So long as our interactions are timed to the babies’ activity they pay attention to us.31 As noted, babies have been shown to copy adult facial expressions but in reality most of the copying goes in the other direction. That’s why they don’t like adults who hold impassive faces.32 On the other hand, adults who engage in an overly animated manner, too much ‘in your face’ as it were, are equally upsetting.33 The perfect combination is one of harmony with infant–adult interactions coordinated in a synchronized ballet of behavioural exchanges.34 For the baby, it is as if the first six months have all been about discovering that they are human and paying attention to other humans. Now the task switches to constructing their unique sense of self.