In 1979, identical twins Dean and David Kopsell took part in a study I conducted on cooperation and competition between twins. They were 9 years old at the time, a highly compatible pair who worked together on their puzzle task with skill and motivation. The smiles on their faces reflected the joy they felt in a job well done. Their IQ scores were well above average and perfectly matched.

Today, at 29, Dean and David are both finishing doctoral degrees in horticulture at the University of Georgia and are seeking similar research positions at the same institution.

How did the Kopsell twins come to walk the same career path? What has made me a researcher and not an investment banker, another person a teacher and not a ditchdigger? And why do some people find their jobs gratifying, while others experience only the daily grind? Since we spend most of our waking hours in the workplace, these questions are key.

Increasingly, researchers have been turning to identical and fraternal twins for answers, with dramatic results. They are finding that genetics, in addition to familial interests, educational, social and other environmental pressures, have a considerable impact on how we choose what we do--and how happy we are with that choice.

Twins reared apart, one University of Minnesota study showed, chose jobs that were similar in terms of complexity level, motor skills and physical demands. In other studies, twins have been shown to have similar tendencies when it comes to enterprising, conventional and artistic undertakings; they also share basic interests, be they science, the pastry arts or public speaking. In both sets of measurements, the similarities between identical twins are greater than between fraternal twins.

Is Everybody Happy?

But it's not only the content of our work that is influenced by genes. Studies with twins have shown us that our satisfaction on the job may be at least 30% attributable to genetic factors. This finding is intriguing because it seems to be related to intrinsic job satisfaction-questions of challenge or achievement-rather than extrinsic factors such as work conditions or supervision. In other words, internal rewards that come from teaching students or composing music, for example, affect the twins' job satisfaction in more similar ways than working late hours or having an irate boss. This makes it easier to understand why identical twins reared apart chose similar occupations-their matched genetic predisposition probably steered them toward tasks at which they both excelled and which brought them joy, pride and satisfaction. People in general may, therefore, better understand their level of job satisfaction in terms of how well their abilities and opportunities coincide.

People bring a unique predisposition or set of expectations to the workplace that may be harder to modify than previously thought. And though tinkering with the lighting or buying a better printer or hiring companionable staff may improve job satisfaction, it may not help as much as one might hope. These same genetically influenced tendencies, in more satisfied types, may help explain why some people persist at interesting or fulfilling jobs even when they offer only modest pay or slim hopes of advancement. When we like what we do we may be more tolerant of troubles that arise from time to time in any work.

Job satisfaction may also partly be affected by our characteristic happiness levels. Recent twin research showed that the genetic contributions to happiness and stability are about 50% and 80%, respectively, while life events have only a transitory effect on happiness. How does this work on the job? A bonus may momentarily elevate the satisfaction of an upbeat worker, but is unlikely to sustain it. Longer coffee breaks may lighten the loathing of a despondent employee, but won't alter his outlook for long. Moreover, two individuals with equally well-matched talents and tasks may vary in job satisfaction if one is typically happy and the other is typically depressed.