Quantum Math Makes Human Irrationality More Sensible

If you’re guilty of making a decision that didn’t make any rational sense, you might now have a great excuse for your irrational behavior. New research has taken a step forward in modeling human judgment and decision-making using mathematics.

Some psychologists have, in fact, spent their careers mocking people for irrational choices when presented with artificial situations amenable to statistical analysis. Sometimes, there really are cases where people make choices that don’t seem rational. One renowned example involved asking students whether they would buy a ticket for a Hawaii vacation in three different conditions: They had passed a big test, they had failed the test, or they didn’t yet know whether they had passed or failed. Many said stated they would buy the ticket if they had passed. Even more, claimed they would buy the ticket if they failed. But 30 % said they wouldn’t buy a ticket until they found out whether they had passed or failed.

It seems peculiar that people would decide to buy the ticket as soon as they knew the outcome of the test but hesitated when the outcome was unknown. Such behavior didn’t follow the statistical maxim called “sure thing principle”, which says that if you prefer X if A is true, and you prefer X if A isn’t true, then you should prefer X whether A is true or not. So it shouldn’t matter whether you know if A is true. This flow seems logical, but it’s not always how people behave.

In recent years, a number of investigators have opined that such supposedly irrational choices merely reflect the fact that people’s brains are steered by the mathematical principles of quantum physics.

Jerome Busemeyer of Indiana University and collaborators write in a recent paper on arXiv.org, “Twenty years ago, a group of physicists and psychologists introduced the bold idea of applying the abstract principles from quantum theory outside of physics to the field of human judgment and decision making. This new field, called quantum cognition, has proved to be able to account for puzzling behavioral phenomena that are found in studies of a variety of human judgments and decisions.”

For instance, a violation of the ‘sure thing principle’ can be explained using quantum math. This was shown by Jose Acacio de Barros of San Francisco State University and Gary Oas of Stanford in another recent paper on arXiv.org. Whether to buy the ticket to Hawaii or not can be regarded as a double-slit quantum interference experiment, where an electron passes through a screen having two slits in it and lands on a detector surface. If one of the slits is closed analogous to pass or fail on the Ticket to Hawaii test, the electron behaves like a particle and lands at a precise spot on the screen. If the two slits are open, implying the test outcome is unknown, the electron behaves like a wave, making it impossible to determine which slit the electron actually passed. The electron wave interferes with itself, changing the probabilities of where it will land on the screen.

A recent quantum mechanical analysis shows that those quantum probabilities violate the sure thing principle predictions, just as the psychology students did. Most recently, a quantum analysis was invoked to explain the puzzle of ‘context effect’ where public opinion polls get different results when the same questions are asked in a different order. This paradox can be explained by quantum probabilities, as reported by Zheng Wang and Tyler Solloway of Ohio State University, collaborating with Busemeyer and Richard Shiffrin of Indiana, on June 16 in the Proceedings of the National Academy of Sciences.

According to researchers at Indiana University and Ohio State University, “Quantum cognition” may explain our decisions when we don’t have a definite feeling about which option to choose or which decision to make. Jerome Busemeyer and Zheng Wang recommend that all options we could possibly make co-exist with varying potential to be chosen. Once a choice is made, all other possible options no longer exist in our minds. Wang proposes that in quantum theory the superposition principle allows uncertainty where classical models only allow changes from one definite to another.

According to Wang, “Our beliefs don’t jump from state to state, instead we experience a feeling of ambiguity about all of the states simultaneously”.

Quantum theory lets the mind to move between each option in a state of indecision until the moment the decision is made.

Quantum theory is usually thought of as describing the behavior of sub-atomic particles rather than human behavior. Our current probability models are based on Newtonian physics and are not automatically suited to modeling the ambiguity of the human mind. In contrast, the possibility of uncertainty permitted in a quantum system more adequately describes some aspects of cognitive behavior.

Wang and colleagues write, “If we replace ‘human judgments’ with ‘physical measurements and replace ‘cognitive system’ with ‘physical system,’ then these are exactly the same reasons that led physicists to develop quantum theory in the first place.”

Since various options regarding a decision to be made can easily be imagined as existing simultaneously, the quantum theory fits behavioral patterns of the mind more easily than even the subatomic particles with which it is primarily concerned.

Many researchers are looking into the idea that our brain is an actual quantum computer, but Wang and Busemeyer’s collaboration is using the quantum model to explain how our decision making might work, without suggesting that the brain can, in fact, perform real quantum information processing.

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