For this little experiment you will need a pen.
Hold the pen lightly in your lips. Then read the following statement: Why don’t oysters ever donate to charity? Because they are shellfish!
Now, take the same pen and hold it in your teeth. Now read: Where is the English Channel? I’m not sure. We don’t get it on our TV!
Which statement did you find funnier? Typically, irrespective of whether it’s jokes, stories or comics people find things funnier when they hold the pen in their teeth than when they hold it in their lips.
This is because of something called embodied cognition. In plain language, our thoughts and emotions are affected by the position or sensations in our body; and vice versa. This stands to reason since the only real reason we think at all is so we take the necessary actions to survive or mate. Cognition isn’t simply a brain thing.
Some weird examples:
Warmth
When people feel socially rejected, they start wanting a hot drink to warm up; and when people are holding a warm drink, they rate themselves closer to important people in their lives than when they hold a cold drink.
Cleanliness
Shakespeare was right when he had Lady Macbeth say “Out damn spot, out I say!”: people actually do have a greater desire to wash after their morals are threatened; and conversely, feel transgressions are less morally wrong when they wash their hands.
Posture
People who were criticized when lying down had less left precortical activity (the part of the brain that goes into overdrive when we experience extreme emotion) than those sitting down.
Darkness
People are more likely to cheat in the dark, or act selfishly when wearing sunglasses.
Smiling
Back to the pen and the jokes. When you held the pen in your teeth it moved your face’s smiling or zygomatic muscles. The brain assumes the fact you are smiling means the joke is funny. Conversely, holding the pen between your lips prevented these muscles being activated, so you assume it isn’t funny.
So next time you’re trying to influence how someone feels, think first about how their body feels. If you want people to warm to you, turn the thermostat up or serve hot drinks; to accept an idea or bad news, make them comfortable…literally; or to take your arguments seriously, put them in a weighty folder!
Reference
For a great summary of all this research and more in this area see:
Barbara Isanski and Catherine West. The Body of Knowledge: Understanding Embodied Cognition http://www.psychologicalscience.org/observer/getArticle.cfm?id=2606
usable psychology 
Aha! So perhaps this might explain while I find it revitalising on my 10k run when I try smiling instead of wincing? I am zygomatically fooling my brain into thinking it is fun. This form of embodied cognition must surely be directed at survival; the state I’m in after 5k makes attracting a mate very unlikely.
Nice comment Chris…big zygo result. Though it could be argued, from an evolutionary perspective, that displays of athletic prowess are totally about attracting a mate and nothing to do with survival 🙂
A worrying thought Tony; my run route is around the infamous Clapham Common. Thanks for the warning.