If you’ve ever stayed in a relationship too long or stuck with a project that was going nowhere, you’re not alone. Humans are generally reluctant to give up on something they’ve already committed time and effort to. It’s called the “sunk costs” phenomenon, where the more resources we sink into an endeavor, the likelier we are to continue—even if we sense it’s futile.

But why would we engage in such potentially self-defeating behavior?

Georgia State University researchers think two factors may play a role. First, it may be a deep, evolutionarily ancient mechanism that helps us balance overall cost and benefit. Second, it may be influenced by uncertainty about the outcome (you never know; it might work out, so why not keep trying?)

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