Geeks and geezers are two words not likely to appear in the same sentence. Elderly eccentrics are often described as geezers, while cutting edge computer fanatics have come to be known as geeks. But they share the title of a new book called Geeks and Geezers: How Era, Values and Defining Moments Shape Leaders. Authors Warren Bennis and Robert Thomas are experts on leadership and change who set out to explore differences between America's oldest and youngest entrepreneurs and reformers.

Sidney Rittenberg, 81, decided as a young man he wanted to help build bridges between cultures. He's devoted much of his career to promoting business ties between China and the United States, despite the fact that he spent 16 years in a Chinese prison. He now teaches college, where he often lectures on the importance of idealism. "I find myself continually having to encourage students and young entrepreneurs not to be afraid of the future, as long as you're sure that what you're doing is right," he said. "I think some of us in my generation got stamped out as incorrigible optimists, and I think that's something important."

Elizabeth Kao, 34, is a marketing executive at the Ford Motor Company. When she looks at people in Sidney Rittenberg's generation, she too is struck by their positive outlook. "I feel like when they were young, they were full of optimism, whereas I think my generation is possibly a little more cynical," she said.

The difference is also reflected in their choice of heroes. Sidney Rittenberg names public figures like American President Franklin Roosevelt. Elizabeth Kao, reared in an era of celebrity scandals, says her role models are people closer to home, like her parents. It's such distinctions that intrigue Robert Thomas and his co-author Warren Bennis. Mister Thomas says they chose the title for their new book, Geeks and Geezers, as an affectionate way to dramatize the difference between leaders in their twenties and early thirties, and those in their 70s and beyond.

The two groups of rebels and innovators launched their careers in different eras, with different goals. "The geeks have grown up in the digital era, have always known computers and the Internet," said Robert Thomas. "The geezers, by contrast, grew up in an era dominated by significant world events, on the order of the Depression and World War II. And when we asked our geezers what was important to them at age 25 to 30, what we heard over and over again was a desire to achieve a measure of stability, particularly coming out of an era of instability. Whereas what our geeks referred to was their desire to shake things up. With all the growth of the Internet and all kinds of business opportunities, it wasn't just a matter of getting a good job and working your way up the corporate ladder. It was striking it rich early."

In fact, many young leaders expressed impatience with corporate ladders, or other traditional hierarchies respected by their elders. Brian Sullivan was in his mid twenties when he founded a venture capital firm called Rolling Oaks Enterprises. "I never was in the military as most of our predecessors were, especially in the finance and industrial sectors," he said. "So, yes, there seems to be a bit of rebellion against that structure. But we all recognize there has to be a certain amount of structure for a company to have some consistency."

And while Elizabeth Kao works at a huge corporation with a complex chain of command, she too wasn't willing to wait years to make her voice heard. "When I hired into Ford, I was part of the manufacturing leadership program, and there was this flurry of new ideas as we took a look around," she said. "So we did quite a bit with the Ford production system."

Nancy Beardsley: "And do you find yourself dealing differently with people under you?"

Elizabeth Kao: "My feeling is that the people who work for me are a team. It is not a command-control situation but rather that our team gives each one of us the opportunity to shine."

Robert Thomas says younger leaders who may work at several jobs in just a few years, also have a different view of corporate loyalty. "The late 1940s and 1950s was an era when you found a job and stayed with it, and there was a payoff for you in the course of a lifetime," he said. "Whereas for our geeks there was a very strong sentiment that the employers no longer felt responsible to them, and therefore they no longer felt obligated to employers. It was their responsibility to manage their individual careers."

Young leaders like Elizabeth Kao also say they want more balance in their lives. "People in my generation are products of the generation before us, people who were willing to work the massive hours," she said. "I don't want it to come to the point that I to regret that I didn't have children, or that I didn't spend time with them."

But the book also reveals what the two groups have in commonqualities that could be vital for good leadership in any era. Nearly all had some kind of life altering experience that taught them resourcefulness and resilience. For Sidney Rittenberg, it was being isolated in a Chinese prison. "You have to learn how to use your mind in such a way that you are thinking positively to demonstrate to your captors who you are," he said.

Elizabeth Kao says her turning point was the failure of a dot-com company she started with college friends. "This was a huge learning experience, not only why did things fail, but what could I do to avoid that situation the next time," she said.

And Robert Thomas says geeks and geezers haven't just learned from past experiences. "The geezers share in common an openness to learning new things," said Robert Thomas. "And we find similar qualities among our geeks. They don't necessarily read the way the geezers did. This is not a reading culture. However, they do a tremendous amount of traveling. They're very interested in new cultural art forms. So in that respect what they share is an openness to new things."

Robert Thomas says that openness means geeks and geezersfor all their differences can work well together in the same company. And they can learn from each other one group seasoned by war and economic hard times, the other confronting the pioneering possibilities of the Internet age.

Geeks and Geezers is published by Harvard Business School Publishing.