A Look at Humor, Laughter, Tickling and, of course, the Brain
Rebecca RothEverybody smiles and laughs at some time or another. The first laughter appears at about 3.5 to 4 months of age (8) ., way before we are able to speak. The average adult laughs 17 times a day (4) . Even monkeys and apes have some facial expressions that are similar to human smiles. But really, why do we laugh? Why are we not able to tickle ourselves? What part of the brain is responsible for laughter and humor? Why do we say some people have no sense of humor? We never go to the doctor because we feel good or because we think something is funny. Therefore, it is not a clinical problem; that is why there has not been much research done on the topic of laughter and the brain.
Although there is considerable information on the neuronal representation of speech, little is known about brain mechanisms of laughter (2) . While many researchers have tracked the brain mechanisms of depression, fear and anger, they have ignored positive emotions and have just begun to study humor. Their investigations are shedding some light on how the brain processes humor and prompts laughter.
Take this joke for instance: How many Bryn Mawr college students does it take to change a lightbulb? Answer: None, they were all so busy studying that they didn't even notice the light was out. If you found this old joke funny, you will get some activity going on in the brain. Investigations into how humor and laughter influence the brain are leading to a clearer understanding of how positive emotions affect brain mechanisms. This in turn may lead to creative ideas for new therapies for emotion disorders and pain (1) .
The physiological study of laughter has its own name, "gelotology". Research has shown that laughing is more than just a person's voice and movement. Laughter requires the coordination of many muscles throughout the body. Laughter also increases blood pressure and heart rate, changes breathing, reduces levels of certain neurochemicals (catecholamines, hormones) and provides a boost to the immune system (3) . Can laughter improve health? It may be a good way for people to relax because muscle tension is reduced after laughing. Human tests have found some evidence that humorous videos and tapes can reduce feelings of pain, prevent negative stress reactions and boost the brain's biological battle against infection (1) . More studies are needed in this field to uncover whether humor or some other component such as distraction, is the predominant factor in these results.
Researchers believe we process humor and laughter through a complex pathway of brain activity that encompasses three main brain components. In one new study, researchers used imaging equipment to photograph the brain activity of healthy volunteers while they underwent a sidesplitting assignment of reading written jokes, viewing cartoons from The New Yorker magazine as well as "The Far Side" and listening to digital recordings of laughter. Preliminary results indicate that the humor-processing pathway includes parts of the frontal lobe brain area, important for cognitive processing; the supplementary motor area, important for movement; and the nucleus accumbens, associated with pleasure (1). Investigations support the notion that parts of the frontal lobe are involved in humor. Subjects' brains were imaged while they listened to jokes. An area of the frontal lobe was activated only when they thought a joke was funny. A study that compared healthy individuals with people who had damage to their frontal lobes, the subjects with the damaged frontal lobes were more likely to choose a wrong punch line to written jokes and didn't laugh or smile as much at funny cartoons or jokes (1) .
A paper published in the journal Nature has provided information about how the brain is involved with laughter. Electrical stimulation was applied at 85 discrete sites on the cortical surface of the left frontal lobe of a 16-year-old girl (A.K.) undergoing monitoring by intracranial subdural electrodes to locate the focus of chronic intractable seizures. The patient's seizures were never accompanied by laughter. During stimulation A.K. performed a variety of tasks such as naming of objects, reading a paragraph of text, or counting. A small area measuring about 2 cm x 2 cm was identified on the left superior frontal gyrus where stimulation consistently produced laughter. The laughter was accompanied by a sensation of merriment or mirth. Although it was evoked by stimulation on several trials, a different explanation for it was offered by the patient each time, attributing the laughter to whatever external stimulus was present. The duration and intensity of laughter increased with the level of stimulation current. At low currents only a smile was present, while at higher currents a robust contagious laughter was induced (2) .The results suggest that electrical stimulation in the anterior part of the supplementary motor area (SMA) can elicit laughter. The observation that A.K. was able each time to invoke a stimulus context that explained the laughter suggests a close link between the motor, affective and cognitive components of laughter. Analysis suggests that smiling and laughter might involve similar mechanisms which are closely related phenomena on a single continuum. This shows that the areas of the brain that caused laughter in A.K. are part of a larger circuit involving several different brain areas. The movement of face muscles for a smile would be the motor part of humor and the understanding of the joke would be the cognitive, thinking part of humor.
Even though we may know more about what parts of the brain are responsible for humor, it is still hard to explain why we don't laugh or giggle when we tickle ourselves. Some scientists believe that laughing caused by tickling is a built-in reflex because even babies do it (3) . If we tickle ourselves in the same spot our friend tickled us, we do not laugh as we did previously. The information sent to your spinal cord and brain should be exactly the same. Apparently for tickling to work, the brain needs tension and surprise. When you tickle yourself, you know exactly what will happen...there is no tension or surprise. How the brain uses this information about tension and surprise is still a mystery, but there is some evidence that the cerebellum may be involved (3) .Because one part of the brain tells another: "It's just you. Don't get excited". Investigations suggest that during self-tickling, the cerebellum tells an area called the somatosensory cortex what sensation to expect, and that this dampens the tickling sensation (7) . It looks as if the killjoy is found in the cerebellum.
Damage to any one part of the brain may affect one's overall ability to process humor. Peter Derks, a professor of psychology, conducted his research with a group of scientists at NASA-Langley in Hampton. Using a sophisticated electroencephalogram (EEG), they measured the brain activity of 10 people following exposure to a humorous stimuli. How quickly our brain recognizes the incongruity that deals with most humor and attaches an abstract meaning to it determines whether we laugh (6) . However, different people find different jokes funny. That can be due to a number of factors, including differences in personality, intelligence, mental state and probably mood. But, according to Derks, the majority of people recognize when a situation is meant to be humorous. In a series of experiments, he noticed that several patients recovering from brain injuries could not distinguish between something that was funny and something that was not. As follow-up to his latest research, Derks has been trying to identify the connection between mood and responsiveness to humor. Derks had originally thought that mood played a vital role in whether a person responded to humor. Someone feeling happy would be more inclined to laugh at a joke than someone feeling sad. However, early findings suggest that there is no apparent consistent pattern among people. Individuals seem to respond to humor in different ways that can't be predicted from their mood (6) . Derks traced the pattern of brainwave activity in subjects responding to humorous material. Subjects were attached to an EEG and their brain activity was measured when they laughed. In each case, the brain produced a regular electrical pattern. Within four-tenths of a second of exposure to something potentially funny, an electrical wave moved through the cerebral cortex, the largest part of the brain. If the wave took a negative charge, laughter resulted. If it maintained a positive charge, no response was given. During the experiment, researchers observed the following specific activities. The left side of the cortex (the layer of cells that covers the entire surface of the forebrain) analyzed the words and structure of the joke. The brain's large frontal lobe, which is involved in social emotional responses, became very active. The right hemisphere of the cortex carried out the intellectual analysis required to get the joke. Brainwave activity then spread to the sensory processing area of the occipital lobe (the area on the back of the head that contains the cells that process visual signals). Stimulation of the motor sections evoked physical responses to the joke (4) . Emotional responses appear to be confined to specific areas of the brain, while laughter seems to be produced via a circuit that runs through many regions of the brain. Damage to any of these regions can impair one's sense of humor. Derks's work only provides a basic picture of how the brain responds to humor. More comprehensive findings could be made if an EEG, Positron Emission Tomography (PET) scanner and Magnetic Resonance Imaging (MRI) were used on a subject simultaneously. However, only a few laboratories in the world are equipped for such testing.
Dr. Shibata of the University of Rochester School of Medicine said our neurons get tickled when we hear a joke. The brain's 'funny bone' is located at the right frontal lobe just above the right eye and appears critical to our ability to recognize a joke. Dr. Shibata gave his patients MRI scans to measure brain activity. Dr. Shibata tried to find out what part of the brain is particularly active while telling the punch line of a joke as opposed to the rest of the joke and funny cartoons in comparison to parts of the cartoon that's not funny. The jokes "tickled" the frontal lobes. The scans also showed activity in the nucleus accumbens. Activity in the nucleus accumbens is likely related to our feeling of mirth after hearing a good joke and our "addiction" to humor (9) . While his research was about humor, the results could help lead to answers and solutions about depression. Parts of the brain that are active during humor are actually abnormal in patients with depression. Eventually brain scans might be used to assess patients with depression and other mood disorders. The research may also explain why some stroke victims lose their sense of humor or suffer other personality changes. The same part of the brain is also associated with social and emotional judgement and planning.
Laughter is a complex human behavior that occurs unconsciously. While we can consciously inhibit it, we don't consciously produce laughter. That is why it is very hard to laugh on command or to fake laughter. We know that many sensations and thoughts trigger laughter, and that it activates many parts of the body. While we know that certain parts of the brain are responsible for certain functions and tasks, it seems that laughter cannot be traced to one specific area of the brain. Furthermore the relation between laughter and humor is not understood, despite their evident connection.
Humor plays a powerful and unique role in human life with wide-ranging effects on many aspects of functioning. Humor can tie people together, help us cope with daily stress, and have a positive effect on the immune systems (5) .Hopefully, uncovering the brain's specific response to positive stimuli like humor and laughter may lead to new therapies for depression.
Although Derks's early findings suggest that mood has no correlation to responsiveness to humor more studies are needed. I know when I am sad, I do not find many things funny. However, when I am in a good mood I laugh much more readily. Although the purpose of humor and laughter is still largely unknown, having a sense of humor is a key part of our personalities and it can play a powerful role in balancing negative emotions, such as fear and anxiety. If we can increase the humor processing abilities of depressed people then we may be able to combat some forms of depression. Even though there have been few studies of humor's place in the brain, understanding the basis of positive emotions will likely be as helpful as understanding the negative ones.
References1 )Brain Briefings 
2)Electric current stimulates laughter , Nature Journal
4)How Laughter Works 
5)Humor on the Brain 
6)The Heart of Laughter 
06/24/2005, from a Reader on the Web
I find this study of humor fascinating. I have a friend who drives me nuts because she just doesn't get when things are funny. She just doesn't get it and says things that make her sound really dumb because of it. And she has a Phd so she's not stupid. Of course, its in statistics so that should tell me something but I'm not sure what. I want to ask her now if she ever had some sort of trauma to her head just above her right eye but I don't know how to do that without being rude. She knows she is different though. She is not a depressed person at all either so I question the idea that humor and depression are too connected. In fact, I fancy myself as having a really great sense of humor and I've actually been treated for depression. I can be very melancholy to say the least but I laugh more than most people I know. Everything seems funny sometimes. Anyhoo, just felt like sharing. Thanks for the interesting study. Susan Bryant
Humor, jokes and laughter. Jokes spread by word of mouth seem to be the oldest form of humor. This I suspect has been embeded in folklore going back centuries. I am embarking on a research project to try to track down when the general concept of jokes and humor, consciously produced within communities, aproximately first appeared. I would love to hear from anyone with similar research interests. I have started collecting books of jokes and recording TV comedy programs. My latest acquisition is, ''The Peguin Book of Australian Jokes by Phillip Adams and Patrice Newell.'' pub. 1994. The thirty page preface is quite serious reading. Much of the rest of the book kept me crying with laughter whilst on holiday in the Mediterranian last Summer. Happy days. John Grocott