It's easy to tell when a child does not like the food he or she is served!

One of the automatic responses that we seem to have to different events is the display of emotional expressions. The disgust that shows on the face of a child who is given something to eat that they do not like is easy to read.

While playing cards it's important to keep a poker face.

Facial expressions of emotions enable us to respond to others in appropriate ways. If someone is looking very sad, it may not be the best time to crack a joke about their shoes. On the other hand, it may be just what they need. This isn't as simple as it seems at times. While we can display emotions through our facial expressions, we can also hide our emotions. The expression "poker face" is used to describe people who can maintain the same expression throughout a game of poker regardless of how good or bad the hand may be. It seems that some of this control is unconscious and develops by watching others. Some people are also very good at "putting on a happy face". This is a talent that actors need as they use facial expressions to portray emotions to the audience.

Even software designers have not over looked the importance of facial expressions in what makes us human. One of the most significant challenges in computer graphics now is to develop a way of realistically portraying human emotions. This is seen as a challenge as there are a significant number of human facial muscles that are capable of a large amount of expressions. Realistic simulation of muscles requires the simulation of muscle action wrapping around the skull structure, jaw rotation, and folding and stretching properties of skin.

Possibly even more exciting and linked directly to the idea that laughter is good for us, is research that shows that manipulating the facial muscles into particular expressions can even effect the way that we feel. This is known as the facial feedback hypothesis.

Placing a pen in your mouth like this can make you feel better

In one study by Strack, Martin, and Stepper (1988), subjects were asked to hold a pen in their lips only or in their teeth without touching their lips (makes a smile-like facial expression). A control group was set up with subjects holding a pen in their hand. Subjects were then given a number of tasks to do including rating how funny cartoons were. Subjects who had the pen in their teeth rated the cartoons as funnier than the other subjects.

The researchers concluded that just by manipulating facial muscles, one can affect the mood of subject (or at least their ratings of cartoons) and that facial movement that simulates a smile resulted increased funniness ratings. There is still some speculation about what causes this apparent correlation. Some studies seem to show that this may be related to the relative brain temperature that we have. Smiling lets the brain cool down while frowning heats things up.