Tag Archives: capuchin

To the bitter end: primates can also fall into the sunken cost fallacy

People are notorious for not wanting to waste our time and effort — to the point that we’re willing to sink more of both into an endeavor we’re already on even if it is obviously futile. Our primate relatives seem to be the same.

Image credits Dimitri Houtteman.

Our reluctance to give something up after we’ve worked hard to get it, or otherwise invested a lot of time of effort in, is known as the “sunken cost” fallacy. In essence, the more effort you’ve put into something, the likelier you are to keep working on it even if you know it’s for naught.

It hails from our very distant past, in our ancestors and the ancestors of the human race. It’s a mechanism that makes sure our brains won’t give things up easily and instead wait for a return on investment — giving up too early might mean wasted energy, which could very well mean death in the wild. But there are many scenarios in modern times when the sunken cost fallacy is a net drain on our achievements and quality of life.

New research comes to help us understand the roots of the sunken cost fallacy, finding that two of our related species — capuchin monkeys and rhesus macaques — are also susceptible to this behavior.

Money business

“The epitome of the sunk cost is I’ve invested so much in this, I’m just going to keep going,” said Professor Sarah F. Brosnan from the Georgia State University (GSU), the paper’s senior author.

The team believes there are two factors that work together to generate the sunk-cost fallacy. The first is an evolutionary mechanism meant to help us balance costs and benefits. The second factor is uncertainty regarding the outcome: it might work, so why not keep at it?

They tested this hypothesis through a series of experiments with capuchin monkeys and rhesus macaques, finding that both are susceptible to the sunk cost fallacy, especially so when they’re uncertain about the outcome.

Housed at the GSU’s Language Research Center, the primates have both indoor and outdoor areas available to them, either for play or to take place in voluntary, non-invasive cognitive and behavioral research Brosnan says.

In the study 26 capuchin monkeys and 7 rhesus macaques played a simple video game. Through a joystick, they could move a cursor onto a target. If they successfully hovered it over the target as it moved, they would hear a sound and get a treat. If they failed in the task, they wouldn’t get a reward and the game would restart. After they got the hang of it, the team would test the primates on rounds of either 1, 3 or 7 seconds.

“Monkeys have really quick reaction times on these games,” said Brosnan, “so one second to them is actually a long time.”

Most rounds actually only lasted for 1 second, the team notes. From a purely practical point of view, this means that “if you didn’t get a reward after that, it was actually better to quit and start a new round”, according to Brosnan. That’s not what the animals did, however.

“They persisted 5 to 7 times longer than was optimal, and the longer they had already tried, the more likely they were to complete the entire task.”

Uncertainty was a powerful driver here, as the monkeys were less likely to continue the experiment if they got a signal that additional time and effort was required (though they wouldn’t always stop). They see this as an indication that the sunken cost fallacy is a product of evolution, and it’s deeply rooted in our developmental history (since these species are relatively distantly related to us). An animal’s ability to hunt, forage for food, or to wait for an appropriate social context would benefit from such a mechanism.

It also shows that it’s not a product of our higher mental abilities such as rationalization, from our concern to maintain our public image as someone reliable and capable, or anything similar. These factors likely help flesh the fallacy out, but our relatives can’t boast them to the same extent as we do.

Finally, the team notes that their findings show why tenacity isn’t always a virtue. Understanding the mechanisms that tug on our motivations from the shadows may then help us lead better, more fulfilling lives by focusing on what really matters to us.

“We’re predisposed to keep trying,” Brosnan said. “And when we find ourselves sticking with things, we should also be a little reflective. Do I have a good reason to keep trying? Or should I leave with no reward, because it will save me more in the long run? That’s really hard to do. But hopefully we can use our cognitive abilities to help us overcome the emotional heartache of occasional sunk costs.”

The paper “Capuchin and rhesus monkeys show sunk cost effects in a psychomotor task” has been published in the journal Scientific Reports.

Dogs and capuchins judge you as ‘good’ or ‘bad’, hint at the birth of human morality

Humans aren’t the only species who appreciate kindness, a new study shows. Pet dogs and capuchin monkeys have been shown preference for people that help others, pointing to a possible origin of our sense of morality.

Image credits Fathromi Ramdlon / Pixabay.

Personal preference certainly plays a hand but for the most part, humans share an instinctive understanding of right and wrong — a certain innate morality that goes beyond upbringing. Previous studies have shown that children as young as three-months-old can recognize ‘bad’ behavior and have pretty complex responses to it.

But where does this infant morality spring forth from? To find out, Kyoto University comparative psychologist James Anderson and his colleagues tested if other species exhibit this sense of right and wrong. Their tests on dogs and capuchin monkeys show that these species make similar social evaluations.

There’s something fishy about you


The team first tested capuchins in two settings — first to see if they show any preference for ‘good’ people, and then to gauge their attitude to perceived fairness.

The monkeys watched an actor trying to open a container with a toy inside and seemingly fail. He would then present the container to a second actor, who would either help or refuse him. After the show, both actors offered food to the capuchins who had to decide on which one to accept.

They were then shown two actors who began the test with three balls each. One of the actors would request them from his companion who handed all three over. When asked to give them back, he either handed all three balls over or refuse to pass them up. As before, these two actors then offered the monkeys food.

If the second actor helped with the container or returned the balls, the monkeys didn’t show any preference between the offers of food. However, if he refused to help or didn’t hand over the balls, they showed a preference for the first actor, accepting food from him more often.

Suspicious Capuchins.

Yea you better hand them balls back, boy.
Image credits One more shot Rog / Flickr.

The next step was to test if dogs responded more positively to people who helped their owner than to those who refused to do so. Each owner was given a container that he would struggle to open and present to one of two actors. This actor would either help or deny the owner’s request. The second actor remained passive. Both then offered the dog a reward that it had to choose from.

Like the capuchins, dogs didn’t show any preference if the actor helped the owner. If he refused to help, the dogs were more likely to take the second actor’s treat.

There’s something fishy about you

Anderson considers the results as proof that capuchins and dogs make social estimations somewhat similar to those of infants. It’s not necessarily a conscious reaction, but an emotional one.

“If somebody is behaving antisocially, they probably end up with some sort of emotional reaction to it,” he says.

And if capuchins they can pick up on clues in human interaction, it’s almost certain that they can do so with other primates. It’s likely that they rely on this moral code to decide which members of the group are reliable and which are likely to rip them off. Dogs, on the other hand, have a long history shared with humans and have evolved to be very perceptive of human behavior, be it with a dog or another human. In both cases, this capacity to estimate other group members’ worth would help cement social systems by excluding bad cooperation partners.

So it’s not that capuchins or dogs have a burning desire to set the world on a path to righteousness — rather, it’s about trust and reputation:’This monkey won’t return my stuff, so I won’t share my stuff with it.’ ‘This human won’t help mine open his stuff. That’s not something a good member of the pack does, so I’ll be wary of him until I know what he’s about.’

It’s an important skill to have in a situation where cooperating is the only way to survive. On the one hand, it guards individuals from raw deals. On the other, recognizing when you’re doing something ‘bad’ is vital if you are to remain in the group.

It’s possible that our inbuilt sense of morality is rooted in these early social evaluation mechanism.

“I think that in humans there may be this basic sensitivity towards antisocial behaviour in others. Then through growing up, inculturation and teaching, it develops into a full-blown sense of morality,” says Anderson.

The full paper “Third-party social evaluations of humans by monkeys and dogs” has been published online in the journal Neuroscience and Behavioral Reviews.

A capuchin hammering away. Credit: University of Oxford

Monkeys in Brazil make stone flakes, which means some of those ancient tools might falsely be attributed to hominids

A capuchin hammering away. Credit: University of Oxford

A capuchin hammering away. Credit: University of Oxford

Humans and tool use are intrinsic. There’s no way we can imagine life as a human or human ancestor, be it today in our technologically-enabled society or millions of years ago in the wilderness, without tools. Humans aren’t the only tool users in the animal kingdom, however. Ravens, chimps, and monkeys use tools too, scientists will tell you. But while these may seem impressive, hominid tool prowess is unrivaled. Or so we like to think — could we be giving ourselves too much credit?

In the Brazilian forest, a startling find made big waves among anthropologists after a team witnessed with their own eyes how a capuchin monkey turned a plain old stone into a flake — the most basic cutting tool, but one of vital importance. Some of the earliest flakes we’ve found are 3.3 million years old and, naturally, scientists attributed them to human ancestors who lived in those times, like Australopithecus afarensis or Homo habilisIn light of this recent remarkable discovery, however, we can only beg the question: Were all of those tools made by human ancestors? 

Tomos Proffitt, a paleoanthropologist at Oxford University, was there when a capuchin monkey took a rock and bashed it against others. Luckily, Proffitt and colleagues caught it all on tape for the rest of us to see. When they finally descended to the site, they found 111 fragmented stones which the capuchins had dropped. Half of these fractured flakes exhibited conchoidal fracture, a feature commonly associated with hominid flake production.

Capuchin monkeys are pretty clever and you can often see them bash rocks against nuts to crack them open and enjoy their sweet kernel. But this time, the monkeys weren’t cracking nuts — they were cracking stones and in the process produced flakes that, in some respects, rival those found in Africa millions of years ago.

There’s a catch, though. The monkeys didn’t seem to have any idea what to do with the flakes once they made them. The fact that the bashed rocks ended up looking like tools seems to be coincidental. Instead, what the capuchin was after were the minerals from the quartz. These are licked and ingested, the flakes once sucked dry thrown away — or so it seems, anyway.

“While humans are not unique in making this technology, the manner in which they used them is still very different to what the monkeys seem capable of,” said co-author and leader of the Primate Archaeology (Primarch) project Michael Haslam, from the University of Oxford.

Moreover, the ancient tool flakes bear evidence of more intent than what Proffitt and colleagues found in Brazil. Ancient bones which are etched with hundreds of cut marks found in sites alongside flakes also add weight to the idea that, indeed, human ancestors were using such tools with intent millions of years ago. Proffitt, however, cautions that not all of these thousands of flakes collected so far may be made by humans.

“This does not mean that the earliest archaeological material in East Africa was not made by hominins. It does, however, raise interesting questions about the possible ways this stone tool technology developed before the earliest examples in the archaeological record appeared. It also tells us what this stone tool technology might look like. There are important questions too about the uniqueness of early hominin behaviour. These findings challenge previous ideas about the minimum level of cognitive and morphological complexity required to produce numerous conchoidal flakes,” Proffitt said.

It’s not entirely clear why the capuchins do this, though. More investigations might shed some light on this question.

The findings appeared in the journal Nature