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Human behavior is a mystery that fascinates many scientists. And there has been much discussion about the role of probability in explaining how our minds work.
Probability is a mathematical framework designed to tell us how likely an event is to occur - and works well for many everyday situations. For example, it describes the outcome of a toss as ½ - or 50% - because tossing heads or tails is equally likely.
Yet research has shown that human behavior cannot be fully captured by these traditional or 'classical' laws of probability. Could it instead be explained by the way probability works in the more mysterious world of quantum mechanics?
Mathematical probability is also an essential part of quantum mechanics, the branch of physics that describes how nature behaves at the scale of atoms or subatomic particles. However, as we will see, probabilities in the quantum world follow very different rules.
Discoveries over the past two decades have shed light on a crucial role for "quantumness" in human cognition: how the human brain processes information to acquire knowledge or understanding. These findings also have potential implications for the development of artificial intelligence (AI).
Human 'irrationality'
Nobel Prize winner Daniel Kahnemann and other cognitive scientists have conducted research into what they describe as the "irrationality" of human behavior. From a mathematical perspective, when behavioral patterns do not strictly follow the rules of classical probability theory, they are considered 'irrational'.
For example, one study found that a majority of students who passed an exam prefer to go on vacation afterwards. Likewise, a majority of those who have failed also want to go on vacation.
If a student does not know their result, classical probability would predict that they would choose the holiday because it is the preferred option regardless of whether they pass or fail. Yet in the experiment, a majority of students preferred not to go on holiday if they did not know how they had done it.
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Intuitively, it is not difficult to understand that students may not want to go on holiday if they have to worry about their exam results all the time. But classical probability does not accurately reflect the behavior, so it is described as irrational. Many similar violations of classical probability rules have been observed in cognitive science.
Quantum brain?
In classical probability, when a series of questions are asked, the answers do not depend on the order in which the questions are asked. In quantum physics, by contrast, the answers to a series of questions can depend crucially on the order in which they are asked.
An example is measuring the spin of an electron in two different directions. If you first measure the spin in the horizontal direction and then in the vertical direction, you will get one result.
The outcomes will generally be different if the order is reversed, due to a well-known feature of quantum mechanics. Simply measuring a property of a quantum system can affect the thing being measured (in this case, the spin of an electron) and thus the outcome of any subsequent experiments.
Order dependence can also be found in human behavior. For example, in a study published twenty years ago on the effects of question order on respondents' answers, subjects were asked whether they thought the previous US president, Bill Clinton, was honest. They were then asked whether his vice president, Al Gore, seemed fair.
When the questions were asked in this order, 50% and 60% of respondents respectively said they were honest. But when the researchers asked respondents first about Gore and then about Clinton, 68% and 60%, respectively, said they were honest.
On an everyday level, it seems that human behavior is inconsistent because it often violates the rules of classical probability theory. However, this behavior seems to fit the way probability works in quantum mechanics.
These kinds of observations have led cognitive scientist Jerome Busemeyer and many others to recognize that quantum mechanics can, on the whole, explain human behavior in a more consistent way.
Based on this astonishing hypothesis, a new field of research has emerged within the cognitive sciences, called 'quantum cognition'.
How is it possible that thought processes are dictated by quantum rules? Do our brains work like a quantum computer? No one knows the answers yet, but the empirical data strongly suggests that our thoughts follow quantum rules.
Dynamic behavior
In parallel with these exciting developments, my collaborators and I have spent the past twenty years developing a framework for modeling - or simulating - the dynamics of people's cognitive behavior as they process "noisy" (that is, imperfect) information from the outside world.
We discovered again that mathematical techniques developed for modeling the quantum world can be applied to modeling how the human brain processes noisy data.
These principles can be applied to other behaviors in biology, beyond just the brain. For example, green plants have the remarkable ability to extract and analyze chemical and other information from their environment and adapt to changes.
My rough estimate, based on a recent experiment with common bean plants, suggests that they can process this external information more efficiently than the best computer we have today.
In this context, efficiency means that the factory is consistently able to reduce uncertainty about the external environment as much as possible under the given circumstances. Consider, for example, simply detecting the direction from which the light comes from, so that the plant can grow in that direction. The efficient processing of information by an organism is also related to conserving energy, which is important for its survival.
Similar rules may apply to the human brain, especially the way our mood changes when detecting outside signals. All this is important for the current trajectory of technological development. If our behavior is best described by the way probability works in quantum mechanics, then to accurately replicate human behavior in machines, AI systems likely need to follow quantum rules, not classical rules.
I have called this idea artificial quantum intelligence (AQI). Much research is needed to develop practical applications of such an idea.
But an AQI could help us achieve the goal of AI systems that behave more like a real person.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
