A tendency to seek consistency among attitudes, thoughts, and beliefs.

<aside> ℹ️ Cognitive dissonance describes when we avoid having conflicting beliefs and attitudes because it makes us feel uncomfortable. The clash is usually dealt with by rejecting, debunking, or avoiding new information.

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This internal contradiction includes the mental conflict when your beliefs don't reflect your actions. For example; craving fast food, but also wanting to feel healthy, or have the perception that you're someone who cares about fitness.

To understand dissonance, knowing first what consonance is would help. Consonance is when you feel comfortable with your beliefs; a certain harmony exists in how you’re feeling right now. You feel good. Dissonance occurs when something disrupts your consonance. It challenges your beliefs and makes you feel uncomfortable. You feel bad, or you think to yourself, “What the heck is going on?”

Festinger’s basic hypotheses for cognitive dissonance

1. The presence of dissonance, of being psychologically uncomfortable, will motivate the person to try to reduce the dissonance and achieve consonance.
2. In addition to trying to reduce dissonance when it is present, the person will actively avoid situations and information that would likely increase it.

People alleviate cognitive dissonance in one of three ways: by reducing the importance of dissonant cognitions, adding consonant cognitions, or removing or changing dissonant cognitions.

• Lying to themselves (i.e., opting to believe a lie, or excusing an action as "not that contradictory").
• Changing their behaviour (i.e., an animal-lover deciding to not eat meat).
• Adopting a new behaviour (i.e., going for a run to offset eating a cake).

Resources

Cognitive dissonance, Wikipedia

Why is it so hard to change someone's beliefs?