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Study Roundup: Your Brain May Be Responsible for Your Biased Choices

A new Columbia University study helps explain how the hippocampus might make a person irrationally choose one brand of cereal over another—and why otherwise tolerant people could be subconsciously racist.

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-- By Alexia Stevenson

The Gist

A woman making a decision about brands of wine at a grocery store.Have you ever gone out and bought a product simply because you liked the celebrity endorsing it? If you, you can rest assured that you are not alone—and, that the decision may be out of your control. As it turns out, your brain regularly makes biased and irrational decisions. According to a recent study “Preference by Association: How Memory Mechanisms in the Hippocampus Bias Decisions,” published in Science, we unconsciously make decisions based on their association to other valued choices or experiences we’ve had in the past.

For example, if you meet two people, Jane and John, at a party and Jane does something nice for you, but you hardly see John at all, you will unconsciously associate John with Jane and like them both equally. Another example would be choosing a new brand of breakfast cereal because you previously saw it next to one you really liked.

While marketers and consumers are well-aware that we have biases, little research has revealed just how and why these biases are formed. But researchers Daphna Shohamy and G. Elliot Wimmer at Columbia University in New York discovered that the hippocampus, which is already known for its critical role in forming memories, also enables us to make decisions about things we’ve never experienced before.

The Expert Take

To test Shohamy and Wimmer’s hypothesis that an option that isn't highly valued on its own could become more appealing if it were unconsciously associated with another, truly high-value option, they had participants play a computer game that taught them to associate certain images from one group with images from a second group. Later, some of the images from the second group came with a monetary reward.

Functional brain imaging indicated that when participants received money as a reward, it activated unconscious memories of the associated images from the first group and led them to make biased choices based on memories they weren't even aware of.  From then on, participants only chose images from the first group if they were indirectly linked to the monetary reward.

Speaking with Healthline, Shohamy said this mechanism is important in making every day decisions because it allows us to make choices without having ever experienced the benefits it may or may not bring.

 “It means we can be flexible and we are not just limited to things we actually experienced,” she said. “It’s really adaptive.”

The Takeaway

We can draw several insights about how both memory and decision-making work based on the conclusion that the hippocampus enables us to make choices by association:

  1. Preferences emerge from the hippocampus, the part of the brain that forms memories, and contributes to our daily decisions.
  2. Choices are made based on preferences that people are not aware of, suggesting that the hippocampus contributes to an automatic assessment of value.
  3. While it is known that memory can play a part in the decision-making process by retrieving relevant information, this study reveals that the hippocampus allows a person to make biases decisions or have preferences that aren’t based on conscious personal experience.

Shohamy said there are both positive and negative sides to making biased decisions. For example, prejudiced or racist beliefs stem from preference by association. “If one person does something bad, it could cause you to associate that with others who haven’t done anything wrong,” she said.

This study also provides insight into adaptive behaviors and maladaptive behaviors such as addiction.

Source and Method

Thirty-one people participated in this study with three subjects’ data being excluded due to lack of evidence of simple reward learning. Subjects were paid $20 per hour for the approximately 2-hour duration of participation, plus one-fifth of the nominal rewards they earned in the experiment.

Data was collected during three phases: association, reward, and decision making. Additional behavioral data were collected before and after the task.

Other Research

The idea that personal judgments can form misguided beliefs has been contemplated for years, hence the term “guilty by association” and the familiar concept of the halo effect, in which one characteristic of a person can affect the evaluation of the person's other traits.

While no other study has concluded that the hippocampus plays a significant role in making biased decisions, several other studies have looked at the role of the hippocampus in decision-making and learning, such as the 2012 study titled “Generalization of value in reinforcement learning by humans” and the 2012 study, “Dynamics of decision-related activity in hippocampus.”

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The Healthline Editorial team writes about the latest health news, policy, and research.

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