Monkeys also understand when patience is worth it

Monkeys also understand when patience is worth it

Even monkeys understand that patience can pay off. © Karin Tilch

What is going on in our brains when we try to make the best possible decision in a situation? Researchers have now caught such a glimpse into the head of rhesus monkeys. The primates therefore understand very well that in some decisions patience and waiting can pay off in order to make the greatest profit. It was even possible to predict whether the rhesus monkeys decided to wait or move on when looking for food based on their neuronal activity.

When we want to make good decisions, many different considerations go into it. For example, we want to make maximum profit with minimal effort or in the shortest possible time. We experience thought processes like this when we are standing in line at the supermarket checkout and consider switching to the neighboring checkout instead because it might be quicker there. Animals also have to make similar decisions in their everyday lives – especially when they are looking for food. But what is going on in her brain?

Experimental setup
The experimental setup © Neda Shahidi, Xaq Pitkow

Test of patience at the feeder

Researchers led by Neda Shahidi from the University of Texas have now succeeded in following such thought processes in two rhesus monkeys. The animals were asked to search for food in an experimental room with two machines. Each machine dispensed a portion of delicious pellets at the push of a button, but at the same time subjected the primates to a test of patience. Because if they pressed the button a second time too quickly, they would come away empty-handed. However, if they waited patiently, the next time they pressed the button they were rewarded with an even larger portion than the first time. How would the monkeys decide? Wait or move on to the second machine?

“After a while they learned to pay attention to the time since the last key press and also their previous success on a box,” explains Shahidi. “If they waited a while but didn’t receive pellets, they waited even longer before pushing the next time. However, if they weren’t rewarded too many times in a row after pressing the button, they moved to the other box. They seemed to have decided that this food box wasn’t worth the wait and it was better to look elsewhere.”

Brain activity predicts decision

But the researchers were not only able to observe the primates’ behavior, but also what was going on in their heads thanks to wireless technology. Shadidi and her team used electrodes to monitor 96 neurons in the prefrontal cortex of rhesus monkeys. This area of ​​the brain is involved in many aspects of foraging, such as evaluating options, anticipating reward, preparing for action, and perceiving the outcome. A mathematical model ultimately helped the researchers to derive characteristic patterns from the measured neuron activity that were either associated with the decision to wait or to move on.

In this way, Shadidi and her colleagues were finally able to deduce from the activity in the monkeys’ prefrontal cortex what was going on in their heads and which decision they were more likely to make. “We were surprised at how well our model could predict what the monkeys would do in the next few seconds,” reports Shahidi. She and her team now hope to be able to use the knowledge gained to help patients with impaired neuronal processes – such as Parkinson’s or apathy.

Source: German Primate Center; Specialist article: Nature Neuroscience, doi: 10.1038/s41593-024-01575-w

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