You probably laugh at something you find funny, but how much do you really know about jokes and humour? Reader's Digest (RD) questioned several experts to give us some facts about them.

“We can't know the oldest joke in the world because it would have existed earlier than writing,” says Christie Davies, professor of sociology at the University of Reading in the UK. The oldest joke book that's been found so far is the Greek Philogelos. It dates from the 4th century AD, although the jokes date from an earlier time. According to psychologist Steve Wilson, director of National Humor Month (April in the US), it contains 265 jokes.

Rod Martin, professor of psychology at the Western University in Canada, believes that while everyone is born without a sense of humour, as we develop, humour and laughter begin to appear. “Of course, some children are more serious, quiet, and less likely to laugh frequently, but this doesn't mean they don't have a sense of humour.” And according to Steve Wilson, there are no adults who don't have a sense of humour. “Almost everyone is able to develop a sense of humour, and I teach people how,” he says.

Sense of humour does differ a lot by country, according to an author named Scott Weems. British humour is thought to be absurd (荒谬的) in nature, while American humour has an aggressive quality. According to a study, Germans are found to find everything funny.

According to a new study, “prosocial (亲社会的) spending” may be as good for your blood pressure as a healthy diet and exercise. The majority of us believe that the way to become happier and healthier is by spending money on ourselves. We put in extra hours at work and save up money to be able to buy the things that we believe will bring us happiness. But what if spending money on ourselves isn’t the best way to become happier?

Past research has shown that when we spend money on others, we actually experience greater well-being than if we were to spend that money on ourselves. Could something as simple as buying a friend dinner or donating to charity improve our health, too — and if so, how? According to a paper published this February in the journal Health Psychology, it can — and one way it works is by lowering blood pressure.

In an initial study, researchers looked at the relationship between giving money to others(or “prosocial spending”) and blood pressure, a simple measure of cardiovascular (心血管的) health. One hundred eighty-six adults with high blood pressure were asked to report how much money they spent on charities, and then followed up with two years later. By then, the participants who had originally spent the most on charities had lower blood pressure than participants who had spent less money. This association held even after accounting for the effects of income, education level, and age.

Why does prosocial spending have these benefits? One possibility is that it increases how socially connected we feel. Feeling closer to the people we help can improve our relationships with others, which have a large impact on our health.

When we give our money and time to others, research suggests, even giving small amounts of money can be beneficial, and we end up gaining something as a result: We experience increases in health and happiness. In particular, giving to others may help build up our relationships and develop resilience (适应力) in the face of stress.

Have you ever wondered if you see the same colours as other people? Most people know what blue is when they see it. They call it "blue” because they were taught the word and connected it with what they saw. But how do you know what you see as blue isn't someone else's red?

The ability to perceive （感知）different colours is up to receptors （接受器）in our eyes. Light waves hit these receptors and they react depending on which colour the light is, sending signals to the brain. The brain then reads these signals to determine which colour light the eyes are receiving.

Some people's receptors are more developed than others. The inability of the receptor to feel the light waves correctly means that some people cannot tell the differences between similar colours. Those with more developed receptors can see more colours. We sometimes hear people having an argument about whether something is dark blue or black. It might be because one person has stronger receptors to feel the light than another.

In the past, most scientists would argue that everyone saw colours in the same way. However, research was conducted on monkeys, in which their receptors were changed. This enabled them to see more colours than usual. Normally monkeys can only see blue and green, but the change allowed them to see red. Their brains automatically got used to new colours. This suggests that our brains may find new colors of the things we see. Colours could be a very personal experience , unique to everyone.

So, the next time you talk about your favourite colour, just remember if yours is blue and your friend says red, you two might actually be thinking about the same colour. What if everyone in the world has the same favourite colour, but just calls it different names?