Neuroscientists have taught rats to drive tiny cars. They wanted to see if rats could learn new skills and how it affected their brains. The rats did more than expected; they seemed to enjoy the ride. Scientists noticed that the rodents took detours, suggesting they liked both the journey and the destination.
We built our first rat car from a plastic cereal container. After trying different designs, we found that rats could learn to drive forward by holding a small wire acting like a gas pedal. Soon, they were steering with surprising skill to reach a Froot Loop treat. Teaching rats to drive was not just about getting them from point A to point B; it was about seeing how they learned new tasks.
Rats living in enriched environments—places with toys, space, and other rats—learned to drive faster than those in standard cages. This supports the idea that complex surroundings improve neuroplasticity. Neuroplasticity is the brain’s ability to change and adapt throughout life in response to challenges.
After we shared our research, the story of rats driving cars spread quickly. The project continues with new and better rat-operated vehicles, or ROVs, designed by robotics professor John McManus and his students. These improved electric ROVs have rat-proof wiring, strong tires, and comfortable driving levers. They are like a rodent version of Tesla’s Cybertruck.
As a neuroscientist who supports keeping lab animals in natural settings, I found it funny how far we went from our usual practices with this project. Rats usually prefer dirt, sticks, and rocks over plastic objects. Yet here we had them driving cars.
But humans did not evolve to drive either. Our ancestors did not have cars, but they had flexible brains that allowed them to learn new skills like making fire, using language, crafting tools, and farming. After inventing the wheel, humans eventually made cars.
Though cars made for rats are far from anything they would see in the wild, we thought driving would be an interesting way to study how rodents learn new skills. Unexpectedly, we found that the rats were highly motivated during their driving training. They often jumped into the car and started moving the lever before the vehicle was even on the track. Why was this happening?
Some rats training to drive would press a lever before their car was placed on the track, as if they were eagerly looking forward to the ride ahead.
One morning during the pandemic, the rats taught me something important. It was the summer of 2020, a time when many felt isolated, even laboratory rats. When I entered the lab, I saw something unusual: the three driving-trained rats ran to the side of the cage and jumped up, much like my dog does when he wants to go for a walk.
Had they always done this, and I just hadn’t noticed? Were they just eager for a Froot Loop, or were they excited about the drive itself? Whatever the reason, they seemed to feel something positive—maybe excitement and anticipation.
Behaviors linked to positive experiences are associated with joy in humans. But what about rats? Was I seeing something like joy in a rat? Perhaps so, since neuroscience research increasingly suggests that joy and positive emotions are important for the health of both humans and animals.
With that in mind, my team and I shifted our focus. Instead of only studying how stress affects brains, we began looking at how positive events—and the anticipation of them—shape neural functions.
Working with postdoctoral fellow Kitty Hartvigsen, I designed a new plan that used waiting periods to build up anticipation before a positive event. Using Pavlovian conditioning, rats had to wait 15 minutes after a Lego block was placed in their cage before they received a Froot Loop. They also had to wait in their transport cage for a few minutes before entering Rat Park, their play area. We added challenges like making them shell sunflower seeds before eating them.
We called this our “Wait For It” research program. We named this new line of study UPERs—Unpredictable Positive Experience Responses—where rats were trained to wait for rewards. In contrast, control rats got their rewards right away. After about a month of training, we tested the rats to see how waiting for positive experiences affected how they learned and behaved. We are currently studying their brains to map how extended positive experiences affect them.
Early results suggest that rats who had to wait for their rewards showed signs of shifting from a pessimistic thinking style to an optimistic one in tests designed to measure rodent optimism. They performed better on cognitive tasks and were bolder in their problem-solving strategies. We linked this program to our lab’s broader interest in “behaviorceuticals,” a term I coined to suggest that experiences can change brain chemistry in a way similar to medicines.
This research supports the idea that anticipation can strengthen behavior. Previous work with lab rats has shown that rats pressing a bar for cocaine—a drug that increases dopamine activation—already experience a surge of dopamine as they anticipate a dose of cocaine.
It wasn’t just the effects of anticipation on rat behavior that caught our attention. One day, a student noticed something strange: one of the rats in the group trained to expect positive experiences had its tail straight up with a crook at the end, looking like the handle of an old-fashioned umbrella.
I had never seen this in my years of working with rats. Reviewing the video footage, we found that the rats trained to anticipate positive experiences were more likely to hold their tails high than untrained rats. But what did this mean?
Curious, I posted a picture of the behavior on social media. Fellow neuroscientists identified this as a gentler form of what’s called “Straub tail,” typically seen in rats given the opioid morphine. This S-shaped curl is also linked to dopamine. When dopamine is blocked, the Straub tail behavior goes away.
Natural forms of opiates and dopamine—key players in brain pathways that reduce pain and enhance reward—seem to be clues to the elevated tails in our anticipation training program. Watching tail posture in rats adds a new layer to our understanding of rat emotions, reminding us that emotions are expressed throughout the entire body.
While we can’t directly ask rats whether they like to drive, we designed a behavioral test to assess their motivation to drive. This time, instead of only giving rats the option of driving to the Froot Loop tree, they could also make a shorter journey on foot—or paw, in this case.
Surprisingly, two of the three rats chose to take the less efficient path of turning away from the reward and running to the car to drive to their Froot Loop destination. This response suggests that the rats enjoy both the journey and the rewarding destination.
We’re not the only team studying positive emotions in animals. Neuroscientist Jaak Panksepp famously tickled rats, showing their capacity for joy. Research has also shown that low-stress environments change their brains’ reward circuits, such as the nucleus accumbens. When animals are housed in their favorite environments, the area of the nucleus accumbens that responds to rewarding experiences grows. On the other hand, when rats are housed in stressful places, the fear-generating zones of their nucleus accumbens expand. It’s as if the brain is a piano that the environment can tune.
Neuroscientist Curt Richter also made the case for rats having hope. In a study that wouldn’t be allowed today, rats swam in glass cylinders filled with water, eventually drowning from exhaustion if they weren’t rescued. Lab rats handled by humans swam for hours or even days. Wild rats gave up after just a few minutes. If the wild rats were briefly rescued, however, their survival time increased a lot, sometimes by days. It seemed that being rescued gave the rats hope and encouraged them to keep going.
The driving rats project has opened new and unexpected doors in our behavioral neuroscience lab. While it’s important to study negative emotions like fear and stress, positive experiences also shape the brain in important ways.
As animals—human or otherwise—navigate the unpredictability of life, anticipating positive experiences helps drive a persistence to keep searching for rewards. In a world of instant gratification, these rats offer insights into the neural principles guiding everyday behavior. Rather than pushing buttons for instant rewards, they remind us that planning, anticipating, and enjoying the ride may be key to a healthy brain. That’s a lesson my lab rats have taught me well.