Tag Archives: Rhesus

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.

Condomless, reversible male contraceptive treatment shows its worth in rhesus monkey trial

Recent success in a rhesus monkey trial might propel a new type of reversible, condom-free male contraceptive closer to market.

Image credits Astryd_MAD / Pixabay.

We have sex for many reasons — mainly because it’s awesome. But for the most part, the biological incentive, that of procreation, isn’t one of them. Coming up with effective contraceptives that don’t take away from the act’s enjoyment can thus have a huge impact on the quality of life for countless people. A new male contraceptive treatment shows great promise in this regard. It has shown its effectiveness in a new trial, successfully blocking reproduction in a group of rhesus monkeys for more than a year.

Known as Vasalgel, the treatment works by blocking the vas deferens — the tubes that sperm travels down through on its merry way. It forms a flexible, spongy, hydrogel material which allows fluids to pass but holds back sperm cells like a net. In theory, this will allow males to ejaculate but eliminates the risk of unwanted pregnancies altogether.

It’s also very simple to administer — all you need to do is get one injection with long lasting effects. Animal studies so far have also shown that the effects are fully reversible.

Monkey business

The trial took place with 16 male adult rhesus monkeys who received Vasalgel injections. They were then housed for a full breeding season with three to nine fertile females. This was done in a free-living environment to ensure a free, unrestricted interaction between the sexes. Seven of the males were housed with the females for up to two years.

During this time, none of the group’s couplings resulted in pregnancy. The monkeys didn’t show any complications or adverse reactions to the treatment. Based on this trial and previous results from rabbit trials, non-profit Parsemus Foundation is now preparing for the first human trials of the treatment. The company said last year that it hopes to have the treatment commercially available by 2018 with an international pricing structure to ensure that men the world over can afford the contraceptive.

It’s an ambitious goal but with the recent success, it probably still holds strong.

“Contraceptive development is a hugely expensive project,” said Parsemus executive director Elaine Lissner last year.

“But this is not just another early-stage lead; we’re so close on this one. It’s time to finish the job we’ve started.”

Vasalgel was inspired by the work on a polymer contraceptive called RISUG, which is in advanced clinical trials in India; some of the men have been using RISUG for more than 15 years. But right now, only local men near the study sites in India are eligible for the trials, and formal reversibility studies have only been done in animals, not men.

If you’re a guy, you’re pretty limited in the range of contraceptives you can use. Despite huge interest from pharmaceutical companies, this market has remained impressively unchanged in the last century. There are several projects in the works — but most rely on chemical or hormonal regulation of sperm production and still come with a wide range of side effects. So the only established contraceptives are condoms, and vasectomies. The first one isn’t guaranteed to work, the CDC estimating a failure rate of 12%. Vasectomies, on the other hand, are very difficult to revert, which understandably puts a lot of people off.

Vasalgel could make a welcomed addition to the market. By physically blocking sperm, it works similar to a condom. However, you don’t have to keep one handy at all times or put anything on before sex. You also don’t have to unpack and risk damaging it, improving ease of use and reliability. We don’t know exactly how long the gel will last in human users, but that’s something Parsemus has to find out in human trials.

Another huge advantage is that the procedure is reversible. According to Parsemus, the rabbit trials have shown that after Vasalgel was flushed from the critters’ vas deferens, sperm production returned to normal. This removes one of the biggest gripes we have with vasectomies — their permanence.

There still is a lot of work to be done before Vasalgel will come to market, however. The rhesus monkey trial was limited in scope and didn’t include a control group. While unlikely that none of the 16 males managed to charm the females, the results should be taken with a grain of salt. It’s a very good result for Vasalgel, but it’s not a definitive answer.

It’s also worth noting that just because something works in animal studies, it’s not a guarantee that human subjects would see the same results. At least three rounds of human trials are needed before it’s even considered for regulatory approval. But up to now the results are encouraging, so there’s a big chance it will ultimately be green-lighted for human use.

The full paper “The contraceptive efficacy of intravas injection of Vasalgel™ for adult male rhesus monkeys” will be published later this week in the journal Basic and Clinical Andrology.