Are people who have a crush on someone generally delusional with respect to their crush? This question came up in relationships.SE (still in beta) in this lengthy thread (which I hope you can get access to).

Basically the disagreement goes as follows:

Telling somebody with a crush


  It's possible that your crush object may never see you in a romantic light


will let them disregard the 'never' in favor of "possible", because of what DVK calls "confirmation bias" (see note at the bottom). So they would draw possibly false hope from it.

The presupposition is, that people with a crush on someone generally are delusional, at least with respect to said crush, thus suffering from this "confirmation bias".

Now I disagree with the presupposition, but want to put the question, whether it's true or not, here, to ideally get a definitive answer.

Note from DVK's comment:

As a side note - I'm aware that "Confirmation bias" may be a technically incorrect term - call it "Wishful thinking" if you prefer. Basically, the fact that a person with a crush will only hear facts, or interpret anything they hear, in a way that is positive to their desired outcome.
Unrequited love is so common that it is funny. Most childhood crushes begin as such because children are unable to identify who is interested in them. More difficult it becomes when no one is inclined to be in love with them. Being a normal person attachments form to those nearest who show compassion or have some physically appealing trait. Such beings irrational behavior based on the lack of psychological health in a person's life. Therapy can help identify why a person needs love from that individual and why they can't accept the lack of interest. Then it can help identify more suitable candidates for love who bear the same attractable traits. Finally it helps someone develop greater self-esteem and help them move on and cope with the strong pain of rejection. 

Due to the symptoms of their illnesses, those with dependency, attachment or borderline personality disorders are more likely to experience unrequited love or even become obsessed with a person.

In the most extreme and rare form stalking and erotomania can happen as a result of psychosis. These instances are actually disillusion. Normally this occurs with those who have a history of bipolar or schizo typical and are symptomatic, not under a doctors care or taking anti-psychotics.

The literature describes the changes which happen in a normal person's brain caused by love not as delusion but as bias. It has been shown that if you trust someone and you love them your more likely to overlook their faults and systematically misremember their transgressions. Moreover though beauty is in the eye of the beholder it is likewise enhanced by love. The person you love appears more attractive than they would otherwise. This is probably an evolutionary adaption to promote long lasting relationships.