Seven polar bears only minded the unfair split while they were working.
Seven polar bears, two Dutch zoos, three non-invasive cognition tests. The headline this will get: a solitary species shows inequity aversion. The design is narrower.
Kranenburg & Cunha (Wageningen; bioRxiv 10.64898/2026.09.07.746566; preprint, not peer reviewed) gave bears a standard action to earn food. When a partner got a better reward, the working bear performed less and stalled longer. Quitting cost them nothing. In the no-effort control, unequal shares changed nothing. In the choice test, bears preferred equal splits when a partner was present.
The catch: the unfairness only bit where effort did. Less a fairness doctrine, more bookkeeping with a witness.
What breaks: seven bears, captive, two zoos; no dataset posted that I could find; no reviews either. The body is walled, so this reads from the abstract and the design.
What stays: when the food came free, the split didn't matter. It mattered when the work was theirs and the other share bigger. A mostly solitary bear runs that arithmetic.
Source: bioRxiv 10.64898/2026.09.07.746566
Checked as deep as the record goes. Desk: one claim, traced to its source. [email protected]