"I am the greatest!" the great boxer Muhammad Ali famously declared—later adding, "I said that even before I knew I was."

According to a new study published in the journal Psychological Science, Ali's opinion of himself echoes the self-esteem in much of today's youth, who are more confident in themselves and their skills than earlier generations.

Some think the pendulum may have swung too far.

Researchers compared responses from teens in 1975 and 2006, asking questions about their qualities and abilities. The study, published last month, found that today's kids consider themselves to be far more intelligent and capable than their 1970s counterparts, and more likely to report being "completely satisfied" with themselves.

The concern that teens — and especially young women — have low self-esteem has been around for decades, fueled by alarmist media reports and feminist authors such as Naomi Wolf (in her international bestseller "The Beauty Myth").

The supposed self esteem crisis has been blamed on everything from thin fashion models to gender bias in the classroom, yet there's little evidence for a nationwide lack of low self esteem among girls or anyone else.

The new study confirms polls and surveys that find most Americans generally happy with themselves. In one of the largest surveys ever taken of American youth, a 1998 poll surveyed more than a quarter of a million grade-school students; 93 percent of teens said they feel good about themselves.

In fact, according to the study's co-author, associate professor of psychology at San Diego State University Jean Twenge, for today's youth "confidence has crossed over into overconfidence." Too much self-esteem (overconfidence) may be just as damaging as too little self-esteem.

Twenge and other researchers believe that the decades of efforts to boost self-esteem may have created unrealistic expectations in today's youth, and their inflated self-esteem may lead to a sense of entitlement: "I'm great, so I deserve great things."

Despite the popular beliefs, the vast majority of teens are quite satisfied with their bodies, appearance, intelligence, and capabilities. Efforts to instill self-esteem may have done their job too well, and like Muhammad Ali, most people feel pretty good about themselves — whether they should or not.

Benjamin Radford is managing editor of the Skeptical Inquirer science magazine. He wrote about the media and pop culture in his book" Media Mythmakers: How Journalists, Activists, and Advertisers Mislead Us." His books, films, and other projects can be found on his website.