A mathematical theory of human behaviour may re-organise the social sciences in the same way that Darwin’s Theory of Evolution re-organised the biological sciences, according to new research from the London School of Economics and Political Science (LSE).
The article, published in Nature Human Behaviour by Michael Muthukrishna of LSE and Joseph Henrich of Harvard University, argues that current practices in psychological and behavioural science, and some other social sciences, have led to a replication crisis of unreliable results.
The ‘replication crisis’ refers to emerging evidence that the findings of some scientific studies are impossible to recreate and therefore might be wrong. The researchers argue more reliance on a mathematical theory of human behaviour can combat this problem.
This theory, sometimes called Dual Inheritance Theory or Culture-Gene Coevolution, extends mathematical models of population biology and epidemiology to the social sciences. It looks at how changes in our genes and changes in culture (social norms, institutions) can interact. Thus breaking down barriers between biological and social science and drawing together disconnected areas of research such as medicine, sociology, history, and law.
The authors argue without an overarching theory like Dual Inheritance Theory, it can be difficult to connect different areas of research. This means hypotheses about human behaviour can sometimes be subjective and unrepresentative, which can contribute to the replication crisis of results that can’t be reproduced.
Commenting, Michael Muthukrishna from the Psychological and Behavioural Science Department at LSE, said, “For example, past research has suggested people prefer fewer choices to lots of choice. From a more general theory of human behavior perspective, this finding makes no sense or is at least not fully defined. In fact, subsequent work has found there is no evidence that people have a preference for less choice and, if anything, prefer slightly more choice.”
Similarly, the authors argue other studies, such as work on conformity, have suggested people conform to majorities. But trying to understand when and how people do this has been difficult to discover just by experimentation.
The authors suggest predictions can be made more specific using Dual Inheritance Theory, which predicts that people will tend to copy majorities at a rate higher than the size of the majority leading to an S-shaped curve. That is, if 60% of a person’s friends liked McDonalds over KFC, and they didn’t know about either, that person has a more than 60% probability of preferring McDonalds as well.
The theory also mathematically specifies how the shape of the curve changes under different conditions, such as other knowledge, not enough information, the number of choices, how important the choice is and so on. The authors note this S-shaped curve would have been difficult to discover without the underlying theory. These predictions have been tested and repeatedly demonstrated.
Dr Michael Muthukrishna explains, “After the mathematics of Darwin’s theory of evolution were developed, the next step was a Modern Synthesis with other biologists who had thus far been measuring seemingly disconnected aspects of the biological world. With this new theory of human behaviour, the next step is a new synthesis with other social scientists and the measurements and theories across the social world. For the first time in history, we may be approaching something like a general and unifying theory of human behaviour.”