A teenager is being interviewed for a part-time job.

“You’ll get 10,000 yen a week to start off,” says the boss. “Then after a month you’ll get a raise to 15,000 yen a week.”

“Great!” says the teenager, “I’ll come back in a month.”

Canadian researchers used jokes like this in a study of humor published in 1999. Most people found the punch-line funny, except those with damage to the right frontal lobe of the brain. These people, whose brains had been damaged by stroke, tumor or head trauma, preferred an alternative punch-line: “Hey boss, your nose is too big for your face!”

(It’s possible “Beat” Takeshi might prefer the alternative version. That’s just to say that he prefers slapstick, not that he’s actually brain damaged — though you sometimes wonder.)

In any case, the research showed that the frontal region plays a critical role in higher cognitive functions such as humor and emotion. It was conducted by Prathiba Shammi, a psychologist at the University of Toronto, and Donald Stuss, director of the Rotman Research Institute at the Baycrest Centre for Geriatric Care, an academic health-sciences center affiliated to the University of Toronto.

Now Shammi and Stuss have followed up their research into humor by studying it in older adults. They have found that humor appreciation (the emotional response to humorous stimuli — the smile, the laugh — that occurs once the humor has been processed) doesn’t change with age. Older adults still enjoy a good laugh.

However, the ability to intellectually comprehend more complex forms of humor diminishes as the years tick by. The findings are published in the September issue of the Journal of the International Neuropsychological Society.

Participants in the study included 20 healthy older adults (average age 73) and 17 healthy younger adults (average age 28), all right-handed and conversationally fluent in English. They were asked to complete three separate humor tests: appreciation of humorous verbal statements; joke and story completion; and nonverbal cartoon appreciation.

In the first test, participants were presented with 21 humorous and seven neutral written statements and asked to pick out the humorous ones. A humor statement was something like: Sign in a hotel — “Guests are invited to take advantage of the chambermaid.” A neutral statement would be: Sign in a hotel — “Visitors are requested to turn off the lights when they leave the room”.

Older adults, perhaps not surprisingly, performed just as well as their younger counterparts in this first simple test.

In the second test, participants were asked to select the correct punch-lines for 16 incomplete joke stems. Each joke stem had four different endings of which only one was the correct (humorous) punch line.

For example: A neighbor approached Mr. Smith at noon Sunday and inquired, “Say Smith, are you using your lawn mower this afternoon?”

“Yes I am,” Smith replied warily. Then the neighbor answered: “Fine, you won’t be wanting your golf clubs, I’ll just borrow them.” This is the funny correct ending (hey, I didn’t write them, the Canadian researchers did).

Alternatively, there is the slapstick humorous non sequitur ending: “Yow!” said the neighbor, as the rake he walked on slapped his face. Then there is the logical straightforward ending: “Oh well, can I borrow it when you’re done, then?” and the unrelated non sequitur: “The birds are always eating my grass seed.”

In the third test, participants looked at 10 different cartoon drawings. Each cartoon consisted of a series of four similar drawings, only one of which had a funny detail. Participants were asked to select the correct funny version.

Older adults made significantly more errors in the second and third tests, the more cognitively challenging tests.

A series of neuropsychological tests were also administered to assess cognitive abilities such as mental flexibility. Researchers found that as cognitive abilities declined, older subjects made more errors when trying to select humorous punch-lines.

Yet, despite the deficits in humor comprehension, older adults did not differ from the young in their affective responses. In other words, they smiled or laughed when they understood the humor. This suggests that, while cognitive abilities thought to be mediated by dorsolateral frontal regions related to humor may deteriorate with aging, affective processing related to orbital and medial prefrontal regions may remain intact.

“The good news is that aging does not affect emotional responses to humor — we’ll still enjoy a good laugh when we get the joke,” said Shammi. “This preserved affective responsiveness is important because it is integral to social interaction and it has long been postulated that humor may enhance quality of life, assist in stress management, and help us cope with the stresses of aging.”

Here Shammi touches on a question that has been answered with many theories, none of which yet meet with scientists’ complete approval: Why did laughter evolve? What is it for?

Some researchers think it’s all to do with tickling. If chimps and gorillas are tickled they start panting: It’s their form of laughter. Tickling is a means of testing relationships and communicating trust.

And once humans evolved language, laughter could be elicited in almost infinite ways. Perhaps it eased our passage to becoming the animals with by far the most complex of social interactions. It originates in the right prefrontal cortex, and is one of the characteristics that make us human.

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