Often when problem solving, we don’t have the time or cognitive capacity to painstakingly evaluate each solution. Instead, we make an educated guess or rely on our common sense or a rule of thumb. These shortcuts (called “heuristics”) may save us time and cognitive processing, but they don’t always lead to the optimal solution.
Take, for example, the “less is better” effect: valuing a single, high quality object more than that same high quality object plus an object of lower quality. The addition of the lower quality object somehow decreases the subjective value of the higher quality object, even though the quantity of the two objects is greater than the high quality object alone.
This may seem ridiculous, but humans have clearly demonstrated this effect. In one experiment, Hsee (1998) asked participants to indicate how much they would be willing to pay for a set of dishes. In one condition, the set contained 24 dishes. In another condition, the set contained 40 dishes, but 9 of them were broken. Even though the second condition contained more unbroken dishes than the first, the amount that participants were willing to pay for the first set was greater than for the second set. The inclusion of some broken dishes decreased the value of the second set, even though it actually contained more unbroken dishes than the first set.
It’s important to note that participants weren’t comparing the two sets of dishes directly; each participant was only asked to name a price for one set of dishes. Their responses, then, were based on their valuation of the particular set of dishes without additional information or comparison.
When Hsee asked participants to name prices for both sets of dishes, the “less is better” effect disappeared. Instead, participants said that they would pay more for the larger set of dishes than the smaller one. This indicates that humans use comparison information (when it’s available) to make valuation judgments, and we can use this information to overrule heuristics and arrive at the optimal choice. But when we don’t have that comparison information, our heuristics can sometimes steer us wrong.
What about nonhuman animals? Do they rely on similar heuristics when problem solving, and thus make similar suboptimal choices?
Kralik et al. (2012) investigated whether rhesus macaques would also demonstrate the “less is better” effect. In both the lab and a more naturalistic setting, they gave the macaques two options: a more-preferred treat (like a grape), or a more-preferred treat AND a less-preferred treat (like cucumber).
They found that the macaques chose the grape alone significantly more than the grape + cucumber. At first glance, this doesn’t make sense; when given the choice between more food and less food, it’s more evolutionarily advantageous to choose more food. However, it seems that the macaques were more concerned with the quality of the choice than the quantity, and somehow the presence of the less-preferred cucumber lowered the quality of the more-preferred grape. So the decision was instead between lower-quality food (grape + cucumber) and higher-quality food (grape).
It turns out that focusing on quality more than quantity might actually make evolutionary sense: research on the foraging behavior of animals suggests that, when food is scarce, focusing on the quality of food in a particular location (rather than quantity) may lead to more optimal foraging decisions (Do I keep eating at this tree or move on to another one?). Additionally, when food is abundant, averaging the quality of all the food in a particular location will maximize outcome.
So it seems that when solving this problem, macaques rely on a heuristic that may maximize outcome in the wild, even though it doesn’t maximize outcome in this particular task. And, unlike humans, macaques aren’t able to use comparison information to override the heuristic and make the optimal choice. Perhaps factoring in comparison information requires higher cognitive processes that macaques don’t possess, or perhaps macaques just need more experience with the task in order to factor in comparison information.
Either way, the results of these experiments suggest that some heuristics may have an evolutionary origin that predates the split between humans and other primates. And they may have developed even earlier than that: Pattison & Zentall (2014) recently found that dogs also demonstrate the “less is better” effect!
If you’ve enjoyed reading about animal cognition research on this blog, check out Inside Animal Minds, a short NOVA series on animal cognition. The first episode airs tonight at 9 pm on PBS!
Hsee, Christopher K. “Less is better: When low-value options are valued more highly than high-value options.” Journal of Behavioral Decision Making 11.2 (1998): 107-121.
Kralik, Jerald D., et al. “When less is more: Evolutionary origins of the affect heuristic.” PloS one 7.10 (2012): e46240.
Pattison, Kristina F., and Thomas R. Zentall. “Suboptimal choice by dogs: when less is better than more.” Animal cognition (2014): 1-4.