“Little Brain – Big Brain” A (little) myth buster discussion about brain size and intelligence

“Common sense” tells us that having a larger brain is associated with being smart. But is this really true? The last 20 years have confronted us with mind blowing results indicating, that the brain as we mammals know it is not a prerequisite for being smart. In fact, as it turns out, some species don’t even need a brain to come up with impressively intelligent behavior.

But back to the beginning, why writing about brain size in a blog called “Science for Horse Lovers”? Because I have one time too often heard that horses have a small brain and are therefore a bit less intelligent than other animals. Especially when it comes to their flight reaction, there is a certain tendency for humans to react with an unnerved “oh, come on, we have been past this tractor about a 100 times, what is it now?”.

Agreed, sometimes it seems that horses are more difficult to train then e.g. dogs. But here I would always argue that it is not the difference in intelligence, but the fundamental difference in the reactions of a flight animal compared to those of a predator. Moreover, humans and dogs are both predators and therefore, it may be easier for a human to understand the reactions of a dog.

Imagine training a puppy compared to a two year old colt. I would imagine that one of the main challenges in educating a young dog, especially a hunting dog, would be to keep him from running towards an object, while one of the main challenges in educating a young horse will be to keep him from running away from an object. In both situations, we would like to educate them to think first and then run, which is not an easy task in both cases.

However, is it true that horses have a particularly small brain? Figure 1 compares a horse brain in its skull to a human brain in its skull. Agreed, the first impression is, that horses have a rather small brain. However, if we look at the numbers then the horses brain weighs about 400-700 g while the human brain weighs about 1200 g, which maybe a less than the expected difference in weight from the first impression of the pictures.

Thus, is may not be surprising that we have learned over the last two decades that horses are incredibly smart (for an overview over equine intelligence check out the books of Michel-Antoine Leblanc, 2013; Lesley Skipper, 1999; and Paul McGreevy et al. 2018) and can even recognize themselves in a mirror, indicating self-awareness (Mirror test horses: https://www.youtube.com/watch?v=qzo3qFtbceE). A feature, that only very few species possess.

If there is anything that shows impressively how intelligent horses are and how creative they can be when solving problems, then it is their amazing ability to open doors and gates. A study from Konstanze Krüger, Laureen Esch, & Richard Byrne published 2019 in the highly esteemed scientific journal PlosOne investigated this ability using a crowdsourcing design. The authors comped data from lay persons and other public resources, the authors found horses “opening 513 doors or gates on hinges, 49 sliding doors, and 33 barred doors and gateways. The mechanisms included 260 cases of horizontal and 155 vertical bars, 43 twist locks, 42 door handles, 34 electric fence handles, 40 carabiners, and 2 locks with keys. Opening was usually for escape, but also for access to food or stable-mates, or out of curiosity or playfulness. While 56 percent of the horses opened a single mechanism at one location, 44 percent opened several types of mechanism at different locations”. The authors conclude: “We failed to identify a level of complexity of door-fastening mechanism that was beyond the learning capacity of the horse to open.”

Since these are mechanisms, horses are not exposed to in their natural habitat, I find this example of “applied intelligence” awesome! In addition, it seems that horses can also learn this behavior by observing other horses and even humans. An exceptional case of learning an unnatural behavior by observation! (Read the full article at: https://journals.plos.org/plosone/articleid=10.1371/journal.pone.0218954).

In conclusion, there is no doubt that horses are very smart and creative, if they have the opportunity. Unfortunately, not all horses live in housing conditions or are exposed to training methods that allow them to use their intelligence and creativity.

However, since we first talk about it, I would like to ask the somewhat provocative question, how important is it really to have a mammal brain to be smart? The last 20 years of intelligence research have shown some absolutely amazing results. Of course, everybody has probably heard about incredibly smart birds like the Kea, the raven, or the magpie, just to name a few of it. However, recent research on cephalopods (octopuses, squids, cuttlefish, and nautiluses) has revealed truly awesome results! Cephalopods are not only able to solve very complex problems, they can count up to 5, they are creative and use tools, and a recent study from Schnell et al. (2021) has shown that cuttlefish are able to exhibit self-control in a so called “delay of gratification task”.

Delayed gratification is the ability to postpone an immediate gain in favor of a later yet greater reward and is regarded as a sign of high intelligence thought to be important for decision making and planning. In this experiment, it was first determined which kind of prey was preferred by the tested individual. In the test trial, the cuttlefish could earn the preferred prey by deciding not to take the first choice with the less preferred prey. This type of experiment measures impulse control and human children are not able to consistently solve this task before they reach preschool age. Isn’t it amazing that the cuttlefish can solve this strategic task? And, of course, as the reader at this point might have already guessed, a recent study confirms, that horses are also able to solve a delayed gratification task (Brucks, Härterich & König von Borstel; 2022).

The interesting thing is, that cuttlefish are a species totally different from us (we are actually more closely related to insects than to cephalopods) and they have a rather “distributed” brain with the major part located around their esophagus and little parts of their brain located in each of their tentacles. (read more on: https://massivesci.com/articles/cuttlefish-cephalopod-ringed-brains-arms-learning/ ). How mind blowing is this? These results show in any case, that neither brain size nor the kind of brain is fundamental to solve complex problems.

Moreover, this is not all: Probably the most amazing finding within the field of intelligence research, revolutionizing how we understand intelligence is the smartness of an individual which does not even have a cell nucleus, not talking about a brain. It’s “Physarum Polycephalon”, a brainless slime mold, a single-celled amoebae who can remember, make decisions, anticipate change, solves maze tasks, and can choose the healthiest food from a buffet (not all humans manage that one) (Ferris Jabr, 2012 https://www.nature.com/articles/nature.2012.11811). These results have really made scientists rethinking the concepts of intelligent behavior.

Back to the myth that horses have a small brain - well they don’t!

Beyond the fact, that this is a misconception, how much would it matter? It is not size that matters, but behavior, practical problem solving, creativity as well as the ability to communicate that counts. Horses are incredibly smart, they are creative when given a chance, they show empathy and affection, not only within their own species, but also towards other species, including us humans (read my last blog about how horses sense human emotions). Without these features of their mind, we would not be able to experience connection or even be able to handle them.

Nonetheless, the fact remains that in “our world” which also means in our human “habitat” we are the creators of their living environment, the habitat for our horses. And, no doubt, that is because we are the most “intelligent” species on this planet (if we are not finding more surprises in the decades to come). Whether we really are the smartest animals around, needs to be proven. Nonetheless, the task assigned to us humans in the horse-human relationship is to show respect and empathy. We should make a real effort, to appreciate horses as what they are: a highly intelligent, affectionate, and sensitive species!