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[Summer series] Jeanne Hagenbach - Game-changing

The work of Jeanne Hagenbach, researcher at the Center in Economics, Statistics and Sociology of École Polytechnique, reflects the interaction between individuals in mathematical objects through graph theory.

©Silvère Leprovost

In microeconomics, game theory is a unique field of research that analyzes any situation where interacting individuals make decisions. Jeanne Hagenbach, researcher at the Center in Economics, Statistics and Sociology of École Polytechnique, received the CNRS bronze medal in 2016 for her work in this field. Her research focuses on strategic communication, a branch of economics that verges on linguistics.

Understanding how individuals communicate in games

“I try to understand how individuals communicate in games: Who reveals information to whom? What can we deduce when we are told nothing? When do people use vague messages?” explains Jeanne Hagenbach. The situations on which she works all have one thing in common: some individuals have information that others, who need it, do not have. She explores when and how this information circulates. For this purpose, the researcher uses graph theory to represent the incentives of the informed party to lie or manipulate information. “The heart of the problem is that individuals often disclose information in their possession strategically, with the aim of influencing the decisions of others,” she notes. This will be the case for a salesperson trying to persuade consumers of product reliability, for example, or a politician looking to convince voters not to vote for the opponent, or a company that may have an interest in pretending it is withdrawing from a market. The contexts of study are multiple. “Game theory concerns biology, psychology, sociology, economics, politics, and other disciplines. One can model how a male chooses a female to reproduce, how a company chooses the packaging of its products, why passengers leave the metro on the same side, and one can even theorize armed conflicts. It is an entertaining field that offers a lot of freedom while being formal and rigorous”, says Jeanne Hagenbach who discovered game theory in her first year of the Master's program at the Louis Pasteur University in Strasbourg.

"Mathematical fables"

Yet, at the outset she had no intention of becoming an economist. She chose therefore to examine abstract problems and compensate in this way for some gaps in mathematics with innovative and creative research questions. Her work, like theoretical microeconomics in general, sometimes resembles the writing of mathematical fables, and leads more to general teachings than to practical recommendations. “I'm not a communications consultant. I can prove by scientific method that people who resemble one another talk to each other, but this does not tell us how to facilitate communication in a company; it simply gives us directions to follow, "she says.

She is now about to shift her research to new issues. On the one hand, she intends to study the role of doubt in conflicts, using models as well as laboratory experiments. She will thereby explore how the prospect of a situation of struggle between different parties exacerbates differences of opinion and ideology between them. On the other hand, she is planning to strengthen the bridges between linguistics and strategic communication with the aim of gaining a better understanding of the role of vocabulary and its richness. Indeed, if the interests of individuals affect the way they communicate, the language available is also of great importance. Yet words and the weight they carry are seldom studied from the standpoint of game theory. At least not yet.

Find all the portraits of researchers of our summer series, here.