Humans and other primates have inherited similar patterns of illogical behavior through evolution, Laurie Santos, a psychology professor at Yale University, said in a Friday lecture in MooreHall. Santos described her research about three types of non-human primates at the psychologicaland brain sciences department's colloquium, "The Evolution of Irrationality: Insights from Non-Human Primates."
"We often think our behavior and cognition are mostly based on higher-level human intelligence, but when [Santos's] work shows that other primates make decisions in similar ways to us, it helps us realize that much of our behavior derives from evolutionarily older psychological mechanisms," Dartmouth psychology professor Jerald Kralik said in an interview with The Dartmouth.
The "stupid cognition" sometimes exhibited by adult humans is evolutionary in origin, Santos aruged, displaying a photograph of former President George W. Bush holding a book upside down. These irrational behaviors are independent of language, explicit teaching or experience with economic situations, Santos said, noting that human infants and the monkeys she has worked with demonstrate the traits as well.
In her research, Santos found that both Rhesus monkeys and Princeton University undergraduates display anchoring biases, relying too heavily on one piece of information in making decisions. When students were asked to multiply all numbers between one and 10 to achieve one final product, for example, they guessed a smaller number if they began with one times two than if they began with 10 times nine, Santos said.
The monkeys displayed a similar error when researchers put groups of strawberries into a box, Santos said, to determine how they estimated the sum of all numbers from one to five. The monkeys expected a smaller final sum if a single strawberry was put into a box first and a larger total if five strawberries were put into the box first. The monkeys looked at the box for a longer time if the sum was not what they expected, Santos said.
Both the children and capuchin monkeys studied by Santos and her research team exhibited cognitive dissonance, where a subject's preferences are affected by decisions they have already made, Santos said.
Children were shown three stickers that they should have preferred equally -- those depicting a fish, a bee and a butterfly. The children were first asked to choose between the bee and the fish, Santos said. The subject was then asked to choose between the butterfly and the sticker they did not select. Subjects almost always chose the butterfly because they had already rejected the other sticker, Santos said. Capuchins displayed the same results when choosing among red, green and blue candies, according to Santos.
The capuchins were also given a test for irrational economic choices, Santos said. Santos wanted to know if monkeys evaluate a choice relative to a "reference point," like the amount of food they are shown, in the same way that humans do.
"Rather than see the world in absolutes, we see the world in relatives," she said. "We show loss aversion; deviations in the negative direction from the status quo have a great cognitive effect."
The capuchins were given washers as currency and were taught that they could buy food with them. The monkeys were given a choice between two research assistants. One assistant showed the monkeys a single piece of fruit but gave the monkeys two pieces half the time, whereas the other showed them two pieces of fruit but sometimes gave only one. Both researchers gave 1.5 pieces of fruit on average, but monkeys and humans both preferred the assistant showing one piece of fruit, because the choice feels like a gain rather than a loss, Santos said.
Santos, who received her doctorate from Harvard University, lectured at Dartmouth in 2004 at the Summer Institute in Cognitive Neuroscience.
"I had the privilege of being in the lab at Harvard and watching her rise from an undergraduate seeking research experience to being a star in the field," Kralik said, in reference to the two scientists' work together at Harvard's Primate Cognitive Neuroscience Laboratory.
