We all lie to ourselves. Some of us do it more than others but all of us do it. There are obvious disadvantages to self deception. When we deceive ourselves about the nature of reality we are ill-equipped to cope with the problems reality presents. We can't deal with a reality we don't know exists. This makes us vulnerable to threats we don't see until it is too late. We are more likely to be blindsided by misfortune for which we could have prepared if we'd been more honest with ourselves. When extreme, self deception becomes obvious to others, who respond with anything from pity to ridicule. And yet, despite these disadvantages, we all engage in self deception.
So why do we do it? The most widely accepted theory is that - in certain circumstances - self deception serves a protective function. For example, self deception can preserve confidence and self esteem in the face of failure. In the aftermath of tragedy or trauma, self deception can preserve a sense of safety and security we need to move forward. Self deception can motivate us to persevere when the odds are against us. Self deception can help us endure hardship and maintain hope for the future. When the truth is too much to bear we lie to ourselves instead.
On the surface, self deception seems like a paradox. I'll explain. Technically, deception is an intentional act. If I do something intentionally then by definition I am aware that I am doing it. To deceive myself is to intentionally tell myself something that is not true. But if I do this intentionally then I must be aware I am doing it. If I know I am telling myself a lie then don't I also know the truth? And if I know the truth then I haven't really deceived myself, right?
The question, then, is how can someone lie to himself and not know it? To my surprise, there are actually a number of ways this can happen. One method involves information processing and attention. A person can deceive himself by encoding only desirable or welcome information into memory while preventing unwelcome or undesirable information from being encoded. This is essentially a matter of "selective attention," i.e. paying attention to certain aspects of available information while ignoring the rest. This can be done on a conscious level, an unconscious level, or somewhere in between; we may or may not be fully aware of what we're doing.
Another method of self deception is through avoidance. I can keep myself uninformed of information or truths I do not want to know by avoiding activities, situations, or circumstances that might reveal them to me. For example, a wife can avoid discovering her husband's affair by not calling him at work when he claims to be working late. If she did call his work she would be told he'd left hours ago. But she doesn't call because she doesn't want to know.
Self deception can also occur via biased interpretation. Imagine I am presented with a large amount of information, some of which confirms my stance on a particular subject and some that contradicts it. I accept the information that affirms my stance as empirically valid. I decide the information contradicting my stance comes from an unreliable source and is therefore not valid. I may reach this conclusions even if all of the information comes from the same source. Self deception does not necessarally follow the rules of logic.
I'll end with a couple of principles of self deception:
*People do not tell themselves the whole truth if a partial truth is preferable.
*In self deception, people tend to be motivated by what they want to be true.