Yesterday on Postcards, we talked about viewing your career as a pyramid. That's Yahoo (YHOO) CEO Carol Bartz's image. I prefer the idea of a jungle gym. Same point: In today's non-linear, difficult-to-predict environment, you should strive for diverse experience because the step-by-step ladder won't take you far enough.

I was talking about this idea with Claudio Fernandez-Araoz, senior advisor at Egon Zehnder International. He's a globetrotting Argentinian--not a headhunter like most at the big search firm, but a go-to consultant on talent development. His 2007 book, Great People Decisions, is based on research on how the best developers of talent--Southwest Airlines (LUV), McKinsey, Intuit (INTU), Hewlett-Packard (HPQ), and General Electric (GE), among them--manage their high-potential people. These companies stretch their execs in all directions. And the execs learn not just multiple skills but also how to be flexible.

Fernandez-Araoz's latest research involves "competency assessments" of executives in Japan--part of 6,000 or so talent assessments that Egon Zehnder conducts across the globe annually. To his surprise, Fernandez-Araoz told me, "In Japan, unlike in other countries, there's a negative correlation between age and competency." Japanese executives show higher-than-average potential early on, but later they tend to flag, according to Egon Zehnder's research.

Actually, it's not so surprising why "competency"--the firm's measure of fitness for a job--declines as Japanese executives grow older. "Their potential is not being developed because they don't switch jobs and companies and industries," Fernandez-Araoz says, adding that in Japan's age-based HR system, managers tend to get promoted for tenure, not competence. "This limits the development of the high-potentials, while lowering the overall level of competence."

So go ahead, stretch yourself. And think about the four keys to successful leadership, according to Fernandez-Araoz: strategic orientation, results orientation, influence and collaboration, and team leadership. In today's collaborative world--where success also rides on lifting confidence in all around you--team leadership, I'd guess, is most important of all of these.