Eva Rinaldi/Wikimedia Commons
Source: Eva Rinaldi/Wikimedia Commons

Rational beliefs are formed on the basis of solid evidence and are open for appropriate revision when emerging evidence makes them less likely to be true. In contrast, a person with a delusion will hold firmly to the belief regardless of evidence to the contrary.

Examples are the delusion of persecution (everyone hates me), and the delusion of grandeur (the exaggerated belief in one’s self-worth). Such beliefs are subject to reasoning biases, such as jumping to conclusion in making decision on the basis of limited evidence, wishful thinking, and reality denial.

A theory of delusion formation holds that some of or all delusions are motivated (Bortolotti, 2010). For instance, delusion of persecution would be developed in order to point negative events not to the self but to others. Delusions of grandeur seem to protect the person from a low self-esteem. These examples suggest that delusions can have psychological benefits for the person.

A defense mechanism explains the origin of the motivated delusion and its content. As a defensive reaction, motivated delusions can prevent loss of self-esteem and deal with strong negative emotions. People thus hold certain beliefs (often unconsciously) in part because they attach value to them.  To maintain a positive view of themselves, they revise their beliefs in the face of new evidence of good news, but ignore bad news.

In short, motivated delusions can have psychological benefits that might lead both to the formation or maintenance of delusions. Motivated delusions allow the person avoid negative emotions and low self-esteem (McKay et al., 2005).

Everyday motivated delusions (or self-deception) allow desires shape beliefs (Bénabou & Tirole, 2016). For example, a man might believe incorrectly that he is in a happy relationship, when in fact his partner is having an affair. His belief in the fidelity of his partner and the strength of his relationship is very resistant to any evidence that would contradict his firmly held beliefs.

Motivated delusions, however, are ultimately harmful and are likely to bring psychological costs (a form of self-trap). Delusions have an adverse effect on well-being and undermine interpersonal relationships (Coltheart, 2015). For example, individuals with persecutory delusions avoid situations that they perceive as threatening, and they are emotionally anxious with respect to the content of their delusion. Family members of those who suffer from delusions may be strained or broken as a result of the absence of a “shared reality” and common goals.

One could argue that if the psychological benefits of delusional belief outweigh the potential harms, then challenging the delusion is a bad idea (Bortolotti, 2010). Therapists might decide not to challenge a delusion if they think that challenging a person is going to be ineffective or disruptive (Freeman et al., 2004).

This ethical dilemma is demonstrated in the movie Marguerite (2015). Marguerite is a thoughtful examination of an eccentric woman with delusions of grandeur. She is a wealthy woman lover of the music and the opera. She loves to sing for her friends, although she is not a good singer. Both her friends and her husband have kept her fantasy. The film leaves us wondering whether it is advisable to challenge her fantasy? Friends and clinicians urge the family members not to challenge her delusion because making her see the reality will be devastating. Her delusion is part of who she is, and her life would be empty and meaningless without it.


Bortolotti L. Delusions and Other Irrational Beliefs. Oxford University Press; Oxford: 2010.

Coltheart, M. (2015). Delusions. In R. Scott & S. Kosslyn (Eds.), Emerging Trends in the Social and Behavioral Sciences (pp. 1-12). Hoboken, USA: John Wiley & Sons.

Freeman, D., Garety, P.A., Fowler, D., Kuipers,E., Bebbington, P.E., & Dunn, G. (2004). Why do people with delusions fail to choose more realistic explanations for their experiences? An  empirical investigation. Journal of Consulting and Clinical Psychology, 72,671-680.

McKay R, Langdon R, Coltheart M. “Sleights of mind”: Delusions, defences and self-deception. Cognitive Neuropsychiatry. 2005;10(4):305–326.

Roland Bénabou  R &  Jean Tirole J (2016), Mindful Economics: The Production,

Consumption, and Value of Beliefs, Journal of Economic Perspectives—Volume 30, Number 3: 141–164.

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