A new perspective on rationality The foundations of decision theory and game theory are commonly thought to be settled, yet there are many examples of human behaviour which is not rational in the way these theories describe. We spoke to Professor Wolfgang Spohn about his work in re-examining basic normative questions about rationality, which could shift the normative reference point for empirical research. Our model of rational human behaviour has been fundamentally shaped by the development of modern decision theory and game theory. “The basics of these theories are thought to be somehow settled for decades – erroneously,” says Wolfgang Spohn, Professor of Philosophy and the Philosophy of Science at the University of Konstanz. The point is not that these theories are often conflated with the model of homo economicus, which assumes that we are primarily guided by rational self-interest and prioritise our own economic concerns. Such assumptions about specific individual values do not belong to the basic conception of rationality. Still, there are many examples of human behaviour which seem rational, but are not regarded as such by standard decision and game theory. While most research
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tinkers round the edges of existing theory, Professor Spohn aims to re-examine the foundations of rationality in a new Reinhart Koselleck project. “The basic normative questions about rationality are not settled. They are still contentious, and I want to take them in a specific direction,” he says.
Normative theory of rationality Professor Spohn’s inquiry into the foundations of a normative theory of rationality could fundamentally change the reference point for all empirical research. “Empirical research proceeds from the standard normative picture and then tries to find explanations for how and why we deviate. But if that standard reference point is not the correct one, then the focus of empirical research should shift,” he explains.
In traditional decision theory and game theory, formal structures called trees are used to represent different options of the agent and the various ways in which a situation may develop. “Two kinds of nodes are usually distinguished in a tree, the action nodes and the chance - or nature’s - nodes. I want to add a third kind of node, which I call decision nodes,” outlines Professor Spohn. “These decision nodes represent not the options of the agent, but rather the decision situations themselves that she is in, or may get into. They represent possible mental states in which she takes a decision and chooses an action.” The label ‘reflexive’ in the project’s title precisely refers to the reflection on those mental states. The decision nodes as described are something that Professor Spohn believes should be additionally represented within
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