zero-sum thinking
A mindset that frames situations as win-lose, where one person's gain is another's loss. Often used in economics, game theory, and everyday psychology.
When you fall into zero-sum thinking, you tend to overlook possibilities for cooperation.
His zero-sum thinking made the atmosphere within the team worse.
From English 'zero-sum' + 思考 (thinking). The term 'zero-sum' originates from game theory.