Researchers from Israel have developed a method to study the character traits of mice by monitoring their behavior. They hope the research will also lead to a greater understanding of the connection between genes and behavior in humans
One of the basic facts in psychology is that no two humans are alike. People differ in their behavior and the way in which they experience emotions – each has a unique personality and individual characteristics. Many psychologists studying personality today use the five-factor model, also known as the Big Five personality traits. The model was developed in the 80s, and involves charting how high or low an individual is in five traits: Extraversion, agreeableness, conscientiousness, neuroticism, and openness to experience. The assessment is based on a questionnaire – you can fill it out yourself here and check your score in each of the five.
There are two basic requirements for personality models: 1. Results are highly stable for each subject over time, i.e., if the same subject were to fill out the questionnaire today and in the following week, he or she would get similar results. 2. The results show significant variability between subjects. The second part is key, because in order to study personality traits in a population, the model must show as many differences as possible between individuals. The five-factor model meets these demands well, but it, too, is not devoid of problems. The reliance on questionnaires, the cornerstone of the model, is also one of its biggest limitations – it makes the model subjective, and the results might change according to the subject’s mood when filling out the questionnaire.
The problem is exacerbated when attempting to study the personality traits of animals, which have some difficulty in responding to questionnaires. Researchers no longer refer to groups of animals as being composed of identical individuals, recognizing that each has its own characteristics: There are brave and timid dogs, social and shy cats, energetic and lazy goats. Up to date, in studies of animals’ traits, researchers mostly relied on the same questionnaires used for research on humans, save that the people who worked with the animals filled them out. Thus, for example, studies were performed on hyenas and chimpanzees. This method does not solve the questionnaires’ subjectivity problem, and is further dependent on additional factors, such as the relationship between the animals and humans.
A video demonstrating the system that records the behavior of mice in research, courtesy of Dr. Oren Forkosh:
Traits from behavior
Researchers from the Max Planck Institute of Psychiatry and the Weizmann Institute of Science published an article in which they examined the personality traits, or mood, of animals, based only on their behavior, and not on questionnaires. The study was led by Dr. Oren Forkosh, today a researcher at the Hebrew University’s Faculty of Agriculture, and Stoyo Karamihalev from the Max Planck Institute of Psychiatry, under the guidance of Prof. Alon Chen from the Weizmann Institute’s Department of Neurobiology, and in collaboration with Prof. Uri Alon from the Institute’s Department of Molecular Cell Biology, in addition to researchers from the Max Planck Institute and the University of Osnabrück, Germany. “We wanted to observe behavior directly,” Forkosh explains in an interview with the Davidson Institute website. “There is the world of genetics, in which we can measure things with great accuracy, and there is the world of behavior. We wanted to develop a model that would connect these two worlds.”
The researchers chose mice as the model animal. They followed 168 male mice, living in groups of four in large cages, with various devices to climb and hide in. For four days – or more precisely four nights, as mice are nocturnal – the researchers recorded the mice roaming freely in the cage and interacting with the various objects in it. An automatic tracking system installed overhead recognized each mouse and recorded its activity – walking; eating; exploring the objects in the cage; and interacting with other mice, including physical contact and chasing one another. In total, the system recorded 60 different behavior types.
Using statistical tools, the researchers produced four “identity domains,” as they termed them, matching the four types of tempers displayed by the mice. The identity domains were chosen to meet the requirements described earlier: Significant variability among individuals along with stability over time for each individual. Even after the researchers mixed the groups of mice, so that each mouse found itself with three other mice it had not interacted with earlier, the scores each mouse received changed little. The researchers did not name the four domains, unlike the developers of the five-factor model – “We wanted to avoid giving them meaning that they do not have,” Forkosh notes. However, one of the identity domains was greatly linked to dominance.
The researchers later showed that the score each mouse received in the four domains was linked to its performance in different tests, such as memory tests or tests measuring anxiety levels. It was also connected gene expression in the brain, that is, the identity and levels of proteins produced in neurons in the brain. By finding the connection between personality and genes, Forkosh explains, we can better understand the heredity of personality traits, and possibly answer questions such as what is the genetic component of personality disorders.
The key to (studying) happiness
Is this model applicable only to mice, or can it be utilized to identify similar identity domains in other animals, as well? “It is a very broad method, and it can be suited to every animal,” says Forkosh. The researchers have already begun doing so with another animal: Using smart watches and applications installed on smartphones of human subjects, they followed their location, movement, pulse, sleep patterns, and other data. The result, says Forkosh, was not much different from what was shown with the previous subjects. “The same algorithm works on humans – we get a similar personality structure for mice and humans.”
In the future, Forkosh plans to employ this method on additional animals – street cats, cows, and even domesticated chickens, whom he intends to compare with a species of wild chickens. One of his goals, ultimately, is to study happiness in animals. “I believe that it is impossible to study happiness without studying personality,” he says. “In humans and in animals, different individuals finds happiness in different things. According to one of the models, you are happy when your behavior matches your personality”.
Another video showing the system recording the behavior of mice in the study, courtesy of Dr. Oren Forkosh: