Discrimination is action that denies social participation or human rights to categories of people based on prejudice. This includes treatment of an individual or group based on their actual or perceived membership in a certain group or social category, "in a way that is worse than the way people are usually treated". It involves the group's initial reaction or interaction, influencing the individual's actual behavior towards the group or the group leader, restricting members of one group from opportunities or privileges that are available to another group, leading to the exclusion of the individual or entities based on logical or irrational decision making. Not all discrimination is based on prejudice, however. In the U.S., government policy known as affirmative action was instituted to encourage employers and universities to seek out and accept groups such as African-Americans and women, who have been subject to the opposite kind of discrimination for a long time. Discriminatory traditions, policies, ideas, practices, and laws exist in many countries and institutions in every part of the world, even in ones where discrimination is generally looked down upon.