People use, and lose, biases to make decisions

From love and politics to health and finances, humans can sometimes make decisions that appear irrational, or dictated by an existing bias or belief. But a new study from Columbia University neuroscientists uncovers a surprisingly rational feature of the human brain: A previously held bias can be set aside so that the brain can apply logical, mathematical reasoning to the decision at hand. These findings highlight the importance that the brain places on the accumulation of evidence during decision-making, as well as how prior knowledge is assessed and updated as the brain incorporates new evidence over time.

This research was reported today in Neuron.

“As we interact with the world every day, our brains constantly form opinions and beliefs about our surroundings,” said Michael Shadlen, MD, PhD, the study’s senior author and a principal investigator at Columbia’s Mortimer B. Zuckerman Mind Brain Behavior Institute. “Sometimes knowledge is gained through education, or through feedback we receive. But in many cases we learn, not from a teacher, but from the accumulation of our own experiences. This study showed us how our brains help us to do that.”

As an example, consider an oncologist who must determine the best course of treatment for a patient diagnosed with cancer. Based on the doctor’s prior knowledge and her previous experiences with cancer patients, she may already have an opinion about what treatment combination (i.e. surgery, radiation and/or chemotherapy) to recommend — even before she examines this new patient’s complete medical history.

But each new patient brings new information, or evidence, that must be weighed against the doctor’s prior knowledge and experiences. The central question, the researchers of today’s study asked, was whether, or to what extent, that prior knowledge would be modified if someone is presented with new or conflicting evidence.

Source: How people use, and lose, preexisting biases to make decisions