August 4, 2020
Written by: Rebecca Somach
Earlier this year, a study was published that used a very unique method of behavioral testing in animals1. Researchers were able to train rats to do something that doesn’t sound real until you watch videos of it: they trained rats to drive cars. Though the vehicles might not be Formula 1 race cars, they were fully operated and controlled by the rats, leading to the name Rat Operated Vehicles, or ROVs.
The researchers were not just testing whether the rats were able to learn how to drive these cars, but were also interested in understanding if living in an ‘enriched’ environment, as compared to a standard cage, would enhance their ability to drive these cars. The ‘enriched’ environments included toys, different types of bedding materials, and ladders to climb up to different levels in the cage. The researchers found that the animals that lived in these enriched environments took less time on average to enter the car and learn to drive it compared to rats that lived in standard housing. The rats that lived in enriched housing were also more likely to get into the cars even in the absence of a reward. This study’s findings that enriched environments are able to contribute to behavioral outcomes is not a startlingly new revelation2–5 but this is definitely one of the more unique ways to arrive at this conclusion.
Training rats to drive cars might sound like a strange way to study the impact of the environment on behavior, but there are a few important reasons the researchers chose this method. Common behavioral tests for rodents include different types of mazes and object recognition tasks. These are tests for spatial cognition, which is the ability for animals or people to navigate their environment. These tests are pretty simple; most require the animal to do a single thing and learn it well. For example, some mazes require an animal to find the one hole that will lead to an exit out of many holes that won’t. The animal needs to find this same hole in the same location over several days. Researchers usually measure how fast the animal learns to find the hole and whether they go directly to it when they are placed in the maze. This is advantageous for researchers because it is simple to train the animals and the test gives a reliable measurement of their ability to do the task. It is also easier to compare results across different studies that use the same task. However, rodents do not naturally live in simple cages where they learn to navigate the exact same maze over several days. In the woods, city, or if they sneak into a home, rodents navigate lots of different spatial environments for food rewards that are constantly changing locations. They need to deal with different stimuli on a daily basis, just as humans do. When designing tasks to test behavior, researchers need to balance how a task will be challenging enough to really test the animals and how difficult it will be to train and test the animals for research.
The researchers behind the ROV paper believed that training animals in the cars would be a more complex task that would better reflect how animals learn skills that are not initially known to them. Most cognitive tasks used in the lab test skills that most rodents already have—walking and finding food or returning to a home location—while the ROV test is something they have never done before. Now that they have shown rodents can acquire and reliably perform complex, novel tasks, the researchers hope that this type of testing can be used for future studies.
The ROV work is not the only study that used out of the box thinking to investigate behavior. In 2017, a research group in England created a unique task to test the intelligence of bumblebees6. Like rats, bees need to navigate their environment to find food, and then return to their homes. This requires a few skills: navigation, foraging, and memory. Bumblebees are small and have simple brains. It is expected that they can do a few basic tasks and not much more. However, the researchers decided to train bumblebees on a task that is not natural to them at all. The researchers trained the bees to roll a ball into a target zone for a reward of sugar water, almost like a small game of golf. The researchers taught the bees using a model bee on a stick to show them how to roll a yellow ball to the target. They saw that bees were able to learn how to roll this ball to the target. They then had those bees teach a new set of bees this task, this time with three yellow balls, each a different distance away from the target. The new bees were given two tests. The first was testing if they had learned the task. The bees showed that they learned from their teachers and rolled the ball to the target 99% of the time. The next test was called a ‘generalization test’. The researchers again put three balls in the arena and each was a different distance from the target but this time the closest ball to the target was colored black, not yellow. During the test, the bees moved the black ball into the target most often. This means that they correctly learned that the goal of the test was ‘move the ball to the target’ and were not attracted to color or just copying the training of moving any ball to the target. They picked the most efficient way to get their reward, which is by moving the closest ball to the target. The researchers stated that this demonstrated cognitive flexibility as well as the ability of the bees to learn beyond what one would expect of them in nature.
These two studies together might not seem similar at the outset. They are done with very different organisms, and with very different tests. However, the two groups of researchers wanted to go above and beyond the behavioral tests used by many laboratories. They both believed that their tasks were asking these animals to solve novel problems through learning or observation. The researchers needed to get creative since other research that they encountered did not require the animals to do new things. Now, researchers can combine these new tests with other tools, making them powerful forces of research. If a researcher wanted to study whether a gene is required for abstract learning in neurons, they could use genetic tools to get rid of that gene in some animals and then test them in these tasks. If the gene is needed for learning, then those animals would do worse in these tests. If a researcher wanted to know if a treatment or drug could improve cognitive ability, they could give that treatment to some animals and test them with both old behavioral tests and new ones. The power of science is the way that research can build on creativity, and sometimes that might require a group of people building tiny cars for rats.
- Crawford, L. E. et al. Enriched environment exposure accelerates rodent driving skills. Behav. Brain Res. 378, 112309 (2020).
- Bardi, M. et al. Paper or Plastic? Exploring the Effects of Natural Enrichment on Behavioural and Neuroendocrine Responses in Long-Evans Rats. J. Neuroendocrinol. 28, (2016).
- Kempermann, G. Environmental enrichment, new neurons and the neurobiology of individuality. Nat. Rev. Neurosci. 20, 235–245 (2019).
- Neal, S., Kent, M., Bardi, M. & Lambert, K. G. Enriched Environment Exposure Enhances Social Interactions and Oxytocin Responsiveness in Male Long-Evans Rats. Front. Behav. Neurosci. 12, (2018).
- Nithianantharajah, J. & Hannan, A. J. Enriched environments, experience-dependent plasticity and disorders of the nervous system. Nat. Rev. Neurosci. 7, 697–709 (2006).
- Loukola, O. J., Perry, C. J., Coscos, L. & Chittka, L. Bumblebees show cognitive flexibility by improving on an observed complex behavior. Science 355, 833–836 (2017).