How Smart Are Rats? What Experiments Reveal About Rats

Rats and mazes: a century of experiments

The laboratory rat, a domesticated form of the brown rat, became psychology’s favorite subject around 1900. In 1901 the American psychologist Willard Small published one of the first rat maze studies, using a small version of the famous hedge maze at Hampton Court Palace in England. His rats learned the route quickly, making fewer wrong turns with each run.

Later tests showed how flexible this learning is. In the 1940s Edward Tolman argued that rats form “cognitive maps”, mental pictures of their surroundings, because they could take shortcuts they had never been trained to use. In 1976 David Olton and Robert Samuelson introduced the radial arm maze, with eight arms radiating from a center, each baited once. Rats learned to visit each arm without returning to ones they had already emptied, showing a strong working memory.

In the early 1980s the neuroscientist Richard Morris designed the Morris water maze: a pool of cloudy water with a platform hidden just below the surface. Rats quickly learn where the platform is from cues around the room and swim straight to it. The test is still used worldwide to study memory and the hippocampus, the brain area that stores spatial information.

Social learning: rats learn from each other

Wild rats are famously cautious about new foods. The psychologist Bennett Galef and colleagues found how they solve the problem: a rat that smells a food odor on the breath of a colony member becomes more willing to eat that food itself. In other words, rats learn what is safe to eat from their companions.

Social learning can create local traditions. Brown rats along the Po River in Italy were recorded diving for mollusks, a habit that appears to have spread through the colony. Young rats also learn routes and feeding places by following older ones.

Do rats feel empathy?

In 2011 Inbal Ben-Ami Bartal, Jean Decety and Peggy Mason at the University of Chicago published a study in Science in which rats repeatedly learned to open a small restrainer to free a trapped cagemate. They did not open empty restrainers or ones holding toy rats. When offered a second restrainer containing chocolate chips, many rats opened both and often shared the chocolate.

The authors interpreted this as pro-social behavior driven by empathy. Other researchers argued that the rats may simply have wanted social contact, and later experiments by different teams have tried to separate these explanations. A 2015 study from Japan found that rats also helped soaked companions escape from water. Whatever the exact motive, these studies show that rats react strongly to the distress of other rats and will work to end it.

Do rats know what they know?

Metacognition means thinking about your own thinking, such as knowing that you are unsure. In 2007 Allison Foote and Jonathon Crystal reported in Current Biology that rats given a hard sound-length test could choose to skip it for a smaller, guaranteed reward. The rats skipped most often on the hardest trials, as if they knew they were likely to fail.

This was the first claim of metacognition in a non-primate. Some scientists argue that the results can be explained by simpler learning rules, so the question remains open. Even so, rats perform well on tasks once thought to be limited to primates.

Other surprising skills

Rats keep turning up in new kinds of research:

• Regret: In a 2014 study from the University of Minnesota, rats that skipped a good food offer and then met a worse one looked back at the missed option and behaved as if they regretted the choice.
• Driving: In 2019 Kelly Lambert’s team at the University of Richmond trained rats to steer small plastic cars toward a food reward.
• Hide-and-seek: In a 2019 study from Berlin, rats learned to play hide-and-seek with people, taking turns as hider and seeker, and hid more cleverly in opaque boxes.

Rats also make ultrasonic chirps when tickled or at play, which some scientists compare to laughter; read more in do rats laugh?

Rats that save lives

A different species, the African giant pouched rat, has been trained by the Belgian charity APOPO to sniff out explosives and tuberculosis. Its most famous rat, Magawa, found 71 landmines and 38 other pieces of unexploded ordnance in Cambodia and received a gold medal from the British veterinary charity PDSA in 2020. These rats are much larger than brown rats and only distantly related, but they show what a good rodent nose and a quick learner can do.

How do rats compare with other animals?

Rats do not match great apes, dolphins or crows on many tests of problem-solving, and their brains weigh only about 2 g (0.07 oz). Their intelligence is tuned to their way of life: finding food, remembering routes, avoiding danger and living in groups. For a wider comparison, see our list of the smartest animals, or compare rats with another clever mammal in how smart are pigs?