According to Error Management Theory...

When we can use either automatic or controlled thought processes, we choose the one that is the most efficient and the least likely to result in an error.

Biases in our decision$-$making are random and haphazard.

People have to manage the impressions they make, and so they will only present themselves falsely $($make an error$)$ if it will cause the other person to like them more.

When we show biases in our decision$-$making, we do so in the direction that poses the smallest cost to us if we were to make the wrong decision.