Wishful thinking is the formation of beliefs and making decisions according to what might be pleasing to imagine instead of by appealing to evidence, rationality, or reality. It is a product of resolving conflicts between belief and desire. Studies have consistently shown that holding all else equal, subjects will predict positive outcomes to be more likely than negative outcomes (see valence effect). However, new research suggests that under certain circumstances, such as when threat increases, a reverse phenomenon occurs.

Some psychologists believe that positive thinking is able to positively influence behavior and so bring about better results. This is called “Pygmalion effect”.

Christopher Booker described wishful thinking in terms of

“the fantasy cycle” … a pattern that recurs in personal lives, in politics, in history – and in storytelling. When we embark on a course of action which is unconsciously driven by wishful thinking, all may seem to go well for a time, in what may be called the “dream stage”. But because this make-believe can never be reconciled with reality, it leads to a “frustration stage” as things start to go wrong, prompting a more determined effort to keep the fantasy in being. As reality presses in, it leads to a “nightmare stage” as everything goes wrong, culminating in an “explosion into reality”, when the fantasy finally falls apart.

In addition to being a cognitive bias and a poor way of making decisions, wishful thinking is commonly held to be a specific informal fallacy in an argument when it is assumed that because we wish something to be true or false, it is actually true or false. This fallacy has the form “I wish that P is true/false, therefore P is true/false.” Wishful thinking, if this were true, would rely upon appeals to emotion, and would also be a red herring.

Wishful thinking may cause blindness to unintended consequences.