Whether it's because of Chrysler's Lee Iacocca, General Electric's Jack Welch, Tyco International's Dennis Koslowski, Hewlett-Packard's Carly Fiorina or Berkshire Hathaway's Warren Buffet, there's no doubt in Donald Hambrick's mind that CEOs are much more public figures these days than they were 20 or 30 years ago.

"We used to have many more invisible, kind of Steady Eddie CEOs," observed Mr. Hambrick, who teaches management at Penn State's Smeal College of Business.

Mr. Hambrick believes that the rise of the celebrity CEO has been accompanied by increased levels of narcissism in the corporate suite, a trend that raises questions about whether a CEO's inflated opinion of himself or herself affects a company's performance.

"When I tell my friends I'm studying narcissistic CEOs, most often their immediate response is: 'Aren't they all?' "

Research by Mr. Hambrick and Arijit Chatterjee, a Smeal doctoral candidate, indicates that the more narcissistic a CEO is, the more he or she tends to make frequent changes in strategy and pursue larger and more frequent acquisitions. Moreover, the performance of a narcissistic CEO's company tends to be more irregular -- but not worse -- than the performance of companies headed by CEOs who don't have such inflated views of themselves.

"They swing for the fences," said Mr. Hambrick.

The study, "It's All About Me: Narcissistic CEOs and Their Effects on Company Strategy and Performance," is based on 111 CEOs at 105 computer and software firms between 1992 and 2004. The industries were chosen because they presented a large enough sample from which to draw conclusions and because they were populated by CEOs with varying degrees of narcissism. (Some industries such as entertainment have more than their fair share of narcissists, Mr. Hambrick explains.)

Narcissistic CEOs "tended to undertake relatively bold, risky actions, and they generated performance that was either very good or very bad -- and that tended to swing between these extremes," Mr. Hambrick and Mr. Chatterjee write in their study. However, the researchers conclude that CEOs who believe that they are great "do not generate systematically better or worse performance" than their more humble counterparts.

Narcissists take their name from the Greek mythological figure who died because he couldn't stop staring at his reflection in the water. They are convinced of their superiority, crave continued reinforcement of their inflated opinion of themselves, and react to criticism with anger and aggression.

"Narcissists favor the extreme, the grandiose and the colorful," the researchers note in their study. "Incrementalism is too invisible, too mundane to suit the needs of the highly narcissistic CEO. Narcissists need an attentive audience, which in turns means they need drama."

So rather than taking small steps, such as making small improvements in product quality or finding new distributors, they make big changes, including large swings in how much they spend on advertising and research and development. Their fondness for acquisitions reflects their confidence in their ability to run a company better than others, as well as a "desire to make a splash and get the oohs and aahs of the crowd," Mr. Hambrick said.

Still, "It takes a moderate amount of narcissism to be a CEO," he conceded.

Measuring that narcissism presented a challenge. Mr. Hambrick and Mr. Chatterjee doubted CEOs would sit for the type of standardized testing psychologists and psychoanalysts employ to measure a person's narcissism. So they had to rely on five less conventional measures: the size of the CEO's picture in the company's annual report; the number of times a CEO's name appeared in company news releases; the number of times a CEO referred to singular personal pronouns such as "I" or "me" in interviews; and two measures of the CEO's pay compared with the next highest-paid executive.

"The highly narcissistic CEO believes he or she is far more valuable than anyone else in the firm, and this then becomes reflected in the CEO's compensation relative to others," the researchers write.

Mr. Hambrick wanted to use a sixth measure: the size of a CEO's entry in Who's Who. He's convinced CEOs load up their profiles with every merit badge and other honor they've ever earned since childhood, but says the reviewers who passed judgment on the study weren't wild about his indicator.

To confirm that their five measures were valid, Mr. Hambrick and Mr. Chatterjee asked five financial analysts who had covered the industries for at least 10 years for their views on 40 of the CEOs in the study. The analysts' opinion of how inflated a view those CEOs had of themselves corresponded to the researchers findings.

Mr. Hambrick says the study provides fertile ground for future studies, including whether narcissistic CEOs try to hoard the glory in good times and deflect the blame in bad times.

But for the time being, investors, workers and other stakeholders should buckle their seat belts when they sign on with a company with a narcissistic CEO.

"You can pretty much bet on a wild ride," Mr. Hambrick cautioned. "It could be up. It could be down. But it's generally going to be extreme and volatile."