Social facilitation is the tenency for people to be aroused into better performance on simple tasks (or tasks at which they are expert or that have become autonomous) when under the eye of others, rather than while they are alone. Complex tasks (or tasks at which people are not skilled), however, are often performed in an inferior manner in such situations. This effect has been demonstrated in a variety of species. In humans, it is strongest among those who are most concerned about the opinions of others, and when the individual is being watched by someone he or she does not know, or cannot see well.