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 endeavour, the likelier we are to continue, even if we sense it's futile. A new study shows that both capuchin monkeys and rhesus macaques are susceptible to the same behaviour and that it occurs more often when the monkeys are uncertain about the outcome.
The 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?).
They have shown that both capuchin monkeys and rhesus macaques are susceptible to the same behaviour and that it occurs more often when the monkeys are uncertain about the outcome.
According to the research team, these monkeys are housed at their university's Language Research Center, where they have indoor and outdoor areas to live and play in and participate in entirely voluntary and non-invasive cognitive and behavioural research.
In the study, 26 capuchin monkeys and 7 rhesus macaques got to play a simple video game where they operated a joystick, and they needed to move a cursor onto a moving target and keep it there while the target kept moving. If they were successful, they heard a "whoop" sound that indicated success and got a treat. If their cursor lost contact with the moving target, they didn't get a reward and a new round began. After being trained, the experiment tested them on rounds of either 1, 3 or 7 seconds.
The researchers found that both species of monkeys showed sunk cost effects.
Uncertainty played a large part, because when the monkeys got a signal that additional work was required, they were less susceptible to sunk cost behaviour, though they still did demonstrate it.
This is important for several reasons. First, it suggests that this behaviour is likely driven by evolution and deeply embedded across species. Second, it shows that human capacities like rationalization, or human concerns like not giving up on something we have publicly committed to, are probably not the main drivers of the sunk cost phenomenon.
Source: Georgia State University