Zero-sum thinking perceives situations as zero-sum games, where one person's gain would be another's loss. The term is derived from game theory. However, unlike the game theory concept, zero-sum thinking refers to a psychological construct—a person's subjective interpretation of a situation. Zero-sum thinking is captured by the saying "your gain is my loss" (or conversely, "your loss is my gain"). Rozycka-Tran et al. (2015) defined zero-sum thinking as:

> A general belief system about the antagonistic nature of social relations, shared by people in a society or culture and based on the implicit assumption that a finite amount of goods exists in the world, in which one person's winning makes others the losers, and vice versa ... a relatively permanent and general conviction that social relations are like a zero-sum game. People who share this conviction believe that success, especially economic success, is possible only at the expense of other people's failures.

Zero-sum bias is a cognitive bias towards zero-sum thinking; it is people's tendency to intuitively judge that a situation is zero-sum, even when this is not the case. This bias promotes zero-sum fallacies, false beliefs that situations are zero-sum. Such fallacies can cause other false judgements and poor decisions. In economics, "zero-sum fallacy" generally refers to the fixed-pie fallacy.

https://en.wikipedia.org/wiki/Zero-sum_thinking