A team lead position opens in your sales unit. Two people want it.

Mara is your top performer. She has beaten her target by a wide margin three years running, clients ask for her by name, and she has made clear that she sees the promotion as the next step. If she doesn't get it, she may look elsewhere.

Jonas sells solidly but rarely tops the rankings. When new colleagues get stuck, though, they go to him. Two of last year's hires say he taught them how to close their first deals.

You have to recommend one path to your director.

This case moves with you. Make your first call, and the story jumps ahead to show what your decision set in motion. Then you decide again, and your path leads to its own ending. Finally, compare your route with our AI's and with the research.

You & AI · Case 1 · An interactive story

  1. 1Your call
  2. 2What happens next
  3. 3Your next move
  4. 4Our AI and the research

Your first decision: what do you recommend?

Our AI replies to what you write. Please leave out personal details. Privacy

The story continues from your choice. Each path unfolds differently.

Your second decision: what do you do now?

The fix

One possible ending, written by our editors. Real teams vary.

Your path

Our AI replies

Reading your reasoning

Written live by Ati, our AI editor.

Our AI's call: C

"Mara's numbers prove she can sell. They say little about whether she can help others sell, and that is the job. Jonas shows the more relevant signal, but it is one signal, mostly from two colleagues. A short, real leadership task gives both of them a fair chance to show the skill the role needs, and it gives you an honest reason to explain to Mara whatever you decide."

"Where I am unsure: if the role has to be filled next week, I would lean toward Jonas."

What the research says

The best seller is rarely the best boss. Economists Alan Benson, Danielle Li and Kelly Shue studied sales workers at 131 firms. Companies tended to promote their best sellers, and under those new managers the performance of their teams tended to fall. Salespeople who had helped colleagues close deals turned out to be the better managers.¹ Laurence J. Peter gave the pattern its name back in 1969: people rise until they reach a job they can no longer do well.²

Stars depend on their setting. Harvard Business School's Boris Groysberg followed more than a thousand star analysts on Wall Street. Those who moved to another firm saw an immediate and lasting decline in performance; much of their excellence rested on colleagues, networks and resources they left behind.³ We read that as a caution for Mara's case too. Her numbers measure Mara plus the setup around her, and a new role changes that setup.

Becoming a manager means becoming someone else. Linda Hill, also at Harvard Business School, followed 19 new managers through their first year. For star performers, the move turned out to be a deep change in identity, learned mainly through experience. As one new manager put it, nobody had warned them that a promotion could be so painful.⁴

That makes A the classic trap and puts B on firmer ground. C goes one step further: it tests the skill directly before the decision. The studies above don't test trial assignments themselves; we recommend them because they add evidence, treat both candidates fairly and match Hill's finding that people learn this role by doing it.

The AI's call and its replies are written by Ati, our AI editor, and published unedited. Answers are stored anonymously. How we use AI · Privacy

Talent Takeaway

Promote on evidence of the job someone is moving into, and look for the people others already learn from. Your best performer deserves a path too: more scope, harder clients, a role as expert or mentor. A promotion into management is only one way to say thank you.

¹ Benson, A., Li, D., & Shue, K. (2019). Promotions and the Peter Principle. Quarterly Journal of Economics, 134(4), 2085–2134. https://doi.org/10.1093/qje/qjz022

² Peter, L. J., & Hull, R. (1969). The Peter Principle: Why things always go wrong. William Morrow.

³ Groysberg, B. (2010). Chasing stars: The myth of talent and the portability of performance. Princeton University Press.

⁴ Hill, L. A. (2003). Becoming a manager: How new managers master the challenges of leadership (2nd ed.). Harvard Business School Press. See also Hill, L. A. (2007). Becoming the boss. Harvard Business Review, 85(1), 48–56. https://hbr.org/2007/01/becoming-the-boss

Further reading: Boris Groysberg, Chasing Stars (Princeton University Press, 2010), on why top performers so often lose their edge when the setting changes; Linda A. Hill, Becoming a Manager (Harvard Business School Press, 2003), the classic account of the first year in charge; Alan Benson, Danielle Li and Kelly Shue, "Promotions and the Peter Principle" (2019), the large-scale evidence behind the question in this case.