An attitude is an expression of favor or disfavor toward someone or something that influences emotions and behavior. Attitudes can be positive or negative. They are measurable and changeable. Explicit measures rely on self-reports to gauge attitudes, while implicit measures detect unconscious attitudes. Attitudes serve four functions - helping people adjust, providing frames of reference, maintaining self-image, and expressing values. Attitudes have three main components - an emotional or feeling segment, beliefs, and behavioral intentions. Barriers to changing attitudes include prior commitments, strong existing commitments, publicly expressed attitudes, low credibility of new information, insufficient new information, and fear of change.