All parents know that having kids is a blessing - except when it’s a nightmare of screaming fits, diapers, runny noses, wars over bedtimes and homework and clothes. To say nothing of bills is too numerous to list. Some economists have argued that having kids is an economically silly investment; after all, it’s cheaper to hire end-of-life care than to raise a child. Now comes the new research showing that having kids is not only financially foolish but that kids literally make parents delusional (妄想的). Researchers have known for some time that parents with minors who live at home report feeling calm significantly less often than people who don’t live with young children. Parents are also angrier and more depressed than non-parents -- and each additional child makes them even angrier. Couples who choose not to have kids also have better, more satisfying marriages than couples who have kids. To be sure, all such evidence will never outweigh the desire to procreate (生育), which is one of the most powerfully encoded urges built into our DNA. But a new paper shows that parents fool themselves into believing that having kids is more rewarding than it actually is. It turns out parents are in the grip of a giant illusion. The paper, which appears in the journal Psychological Science, presents the results of two studies conducted by Richard Eibach and Steven Mock, psychologists at the University of Waterloo in Ontario. The studies tested the hypothesis that “Idealizing the emotional rewards of parenting helps parents to rationalize the financial costs of raising children”. Their hypothesis comes out of cognitive-dissonance (认知悔悟) theory, which suggests that people are highly motivated to justify, deny or rationalize to reduce the cognitive discomfort of holding conflicting ideas. Cognitive dissonance explains why our feelings can sometimes be paradoxically worse when something good happens or paradoxically better when something bad happens. For example, in one experiment conducted by a team led by psychologist Joel Cooper of Princeton, participants were asked to write heartless essays opposing funding for the disabled. When these participants were later told they were really compassionate -- which should have made them feel better -- they actually felt even worse because they had written the essays.