The sunk cost fallacy describes a common pattern of flawed decision-making in which individuals continue investing time, money, or effort into a losing venture primarily because of resources already invested, rather than on the basis of a rational, forward-looking assessment of the venture's future prospects. From a purely rational economic perspective, past investments that cannot be recovered, referred to as sunk costs, should have no bearing whatsoever on present decisions, since these decisions should logically be based solely on expected future costs and future benefits going forward. Despite this being widely accepted as the economically rational approach, the sunk cost fallacy remains remarkably persistent and pervasive across human decision-making generally, appearing in contexts ranging from personal relationships and career choices to major business investments and large-scale government infrastructure projects. Psychologists studying the phenomenon have proposed several possible explanations for its persistence, including a natural human aversion to consciously acknowledging that resources have been wasted, which continuing to invest can effectively help to psychologically avoid or postpone, as well as broader social pressures to appear consistent in one's decisions and public commitments over time. Notably, this cognitive bias does not appear to be uniquely human; some experimental studies have found that certain animal species also demonstrate sunk cost-like behaviour, persisting longer with a chosen course of action after having invested more effort into it, which has led some researchers to speculate that the underlying tendency may have at least some deeper evolutionary or neurological origins rather than being purely a product of complex human culture and social reasoning alone.