February 28, 2016

In the word birdbrained we describe something (or someone) foolish and short-sighted. This approach makes us value birds as primitive beings whose brains and the thoughts they generate are so elementary and superficial that they cannot compete with human beings.

This is a well-established position, based on fundamental differences in the brain structure of mammals and birds. Humans consider themselves as intelligent, so it is often presumed that only complex mammalian brains can generate complex thoughts and behaviors. And that’s why the complex behavior of birds, observed in the testing ground in many places, is surprising — crows can mislead, and bushes can plan future behaviors.

Breaking the myths of the bird brain 

Compared to most living creatures, the brain structure of the mammals is really impressive — in primates, the cortex occupies more than 70 percent of its total mass. It’s a layer of 2-3 millimeters deep, interwoven and interconnected neurons, and it covers the entire outer part of the brain and forms a lot of folds to maximize the area of the crust that can fit into the skull.

A good illustration of the complex structure of the cerebral cortex is the images from the mouse brain shown below. In order to get a picture on the left, researchers introduced genes into the embryo of mice that cause different groups of cells to produce fluorescent proteins. When these cells evolve into different neurons and take their place in the cerebral cortex, it becomes clear that they are located in different layers. 

This multi-layered cortex is common to all mammals, and presumably has a number of advantages: This separation probably increases the efficiency of neural functions and their connection to other neurons. Why is that? It is logical to assume that brain cells with similar external connections have access to the same information, which means that they have to perform similar functions and can do so more effectively if they communicate with each other.

This approach does not work in the case of birds, as they do not have multi-layered cerebral cortex as in mammals. Their brain structure involves a nucleus, a collection of neurons organized into clusters, so birds don’t have that element of brain structure that we associate with the complex function. We may also be averting intelligence in birds because of the similarity of their brains to so-called basal brain ganglia of mammals.

The photo above demonstrates that these ganglia have no direct connection to each other. Between them is the main nerve fiber channel, which we call the inner capsule, through which information is transmitted to and from the cerebral cortex. It is the presence of nerve fibers between basal ganglia that gives them a striped appearance, making them appear outwardly similar to the brains of birds.

This assessment has dominated science for almost a century, but recent research has made it possible to revise it. Researchers have found that the profile of gene activity in most of the brain of birds is indicative of the origin of the embryonic brain (polio). In mammals, this area is responsible for the multilayered cortex.

This means that the brain of mammals and the brain of birds is more evolutionary than previously thought. Researchers have speculated that both species shared a common nuclear proto-structure that has survived in birds to this day. In these estimates, the structure of the brain of mammals with its vertical layers evolved later, probably because of its high efficiency. This change may have been a qualitative leap forward, giving mammalian brains unprecedented levels of potential. However, researchers have found embryonic manifestations of intelligence in some bird species, which in some ways equates them with primates.

Birds can model the thoughts of other individuals?

During the mating period, European Jay males will feed the interested female, giving researchers the opportunity to test whether the male is able to choose a partner’s food according to her current preferences. In one experiment, researchers fed the females large amounts of specific food, expecting her to get tired of it and be tempted to eat something else. It’s actually a manipulation of a female’s nutritional interests.

The ability to shape one’s behavior with the understanding that other individuals have their interests or wishes is not observed in children under 18 months of age. This has been demonstrated experimentally, with children being asked to choose between two foods for a person who prefers one but cannot tolerate the other. The results showed that children under the age of 18 months choose for other people, the foods they like, without considering the nutritional preferences of the person they are supposed to feed.

The ability to mislead is observed in birds such as crows or Eurasian jays while gathering food. They are able to use a variety of tricks to minimize the risk of detecting food they hide underground or in burrows. If they make a cache in the presence of observers, they wait for the moment when this observer is distracted and only then hide the food.

Some researchers do not believe that to explain this phenomenon, it is necessary to endow birds with advanced mental abilities comparable to those of humans. The scientific doctrine states that the simplest explanation is most often correct.

In an experiment in support of a simple explanation, researchers have found that a «virtual» bush jay can mimic the habit of real-life companions to hide food without any intelligent ability to anticipate the intent of other birds to steal this food. The computer model of a bush jay is designed to follow simple rules of behaviour, including:

  • The desire to hide food from other birds;
  • The intention to move food or hide it more often during stress.

Researchers have found that bushes of jaybirds hide their food in a secret only if they have experienced the theft of hidden food by other birds. 

Why are we reluctant to consider anthropomorphism?

There’s a lot of evidence in the bird world that they know how to discern other people’s intentions and beliefs. Sometimes crows can create false caches, either by leaving them without food, or by filling them with inedible objects, such as stones. If a raven sees that they are being watched, it may display a false interest in empty caches to distract a potential thief from the real food supply. It is noteworthy that people only develop the habit of intentionally misleading someone after four years.

Concepts that explain animal behavior by complex intellectual processes are considered anthropomorphic — humans often seek to endow other animals with human abilities and qualities. But why does it seem illogical to have human qualities in other species? The main mistake of anthropomorphism may be that people believe that their intelligence is an irresistible abyss that separates them from other animals. So scientists prefer to see the endowment of other animals with human intelligence as an extreme measure — a magical explanation of behavior that we think is reasonable. 

P.S. 

If you want to explore this topic in more detail, look at this fascinating article in Science, which describes the African fork-tailed Drongo. He makes false alarms of other species to distract them from eating and thus receives a part of his daily meal.

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