Want to be surrounded by some of the most competitive people on the planet? Work in sales, where paychecks, bonuses, promotions, and stature are usually tied directly to organizational quotas and individual results.

Competition can be a good thing. But often it goes too far — and ironically, performance can suffer for it. Research in recent years shows that sales teams do better when members collaborate with one another. But some salespeople make that almost impossible. Having spent 25 years in this field, I’ve come across some hypercompetitive people who wouldn’t lift a finger to help a colleague and others who clashed regularly with coworkers, getting into arguments that sucked up time and energy.