Choice Bias and the Human Brain: My Choice is Good, Yours is Not

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Do preferences have a biological underpinning? Image by jkt_de.

Do preferences have a biological underpinning? Image by jkt_de.

Is the trinket you chose at the souvenir shop fabulous while your friend’s is just so-so?  Given the choice of two generally equivalent things, people will believe the one they chose is better, attributing positive qualities to it.

Choice Bias and the Human Brain

This cognitive bias, called choice bias, appears to have its underpinnings in brain chemistry and genetics.

In an exclusive interview with Decoded Science, Dr. Jeffrey Cockburn from Brown University, explains the unique aspect of the research:

Prior theories have dealt with choice bias at a psychological level. We’ve approached the choice bias from a neurological level of analysis in an attempt to better understand where these psychological constructs emerge.

Choice Bias and Positive Outcomes

The research  by Cockburn and colleagues is summarized in the press release published by EurekAlert!

80 participants played a computer game in which they could either gain or lose points based on the character with which they play. Sometimes players could pick a character to reveal if it gained or lost a point for them, but other times, they simply received a result.

After figuring out the game, the researchers presented the subjects with the characters in pairs, and asked the subjects to pick the character they thought had the highest chance of winning. According to the researchers, “players showed a clear choice bias.

The subjects were more likely to choose the characters who had resulted in the reward of points, if they had chosen the character – but did not choose the characters they had been assigned, even if that character had been equally-rewarding. Interestingly, the participants didn’t show any preference when it came to characters that made them lose points.

Reward Prediction Errors and the Basal Ganglia

Cockburn and fellow researchers propose a neurological basis for the finding. The brain is designed to be rewarded by bursts of the chemical dopamine, a chemical that produces good feelings. Dopamine is both released and “gated” in a part of the brain known as the basal ganglia.

Dr. Cockburn summarized the feedback loop whereby making a choice biochemically rewards the chooser, something that encourages humans to value the act of choosing over obtaining a reward randomly.  In his interview with Decoded Science, Cockburn explains how the SNr or the active cells in the substantia nigra pars reticulata  inhibit the release of dopamine in the basal ganaglia or BG, and how choice modifies that inhibition:

The SNr (BG) act much like a break on the SNc (dopamine). When the SNr is active (which is its default state, so it’s active most of the time), it inhibits the SNc, effectively acting like a break. If the SNc were to activate when the SNr break was applied, it’s dopamine release would only be moderate because of the SNr dampening its activity. 

He continues:

But, when SNr activity is reduced, as is the case when choice engages the BG, the break on the SNc is reduced. This effectively primes the SNc such that if the SNc is activated once the SNr break has been removed, it will be more active (i.e. more dopamine will be released). 

The SNr/SNc connection forms a feedback loop: When SNr activity is low, SNc activity will be high, and vice versa.<

The end result is that we value a positive reward that occurs when we chose something more than a random reward.  My souvenir is cooler than the one the store gave me for free.

Genetics and Choice Bias

Biology reinforces our choices. Image by pipalou.

Biology reinforces our choices. Image by pipalou.

Cockburn and team also tested participants to see if they carried a genetic variant known as DARPP-32, since they’d found that this genotype predicts choice bias.

In his interview, Dr. Cockburn explained, “C-carriers respond less predictably when faced with a choice between rewarding options, but more predictably when faced with a choice between two aversive options.”

People who carry this gene are genetically primed to avoid negative outcomes.  In Cockburn’s research, participants with this variant showed less of a positive choice bias.

Implications of a Biological Basis for Choice Bias

Dr. Cockburn notes several implications of the research.  One implication is it provides “a more detailed account of why allowing people to choose an item will result in them valuing it more than if you simply gave them that same item.”

Additionally, the research offers a “relatively simple mechanism through which the brain can direct its learning signals to the appropriate regions at the appropriate time.

Dr. Cockburn feels his research also provides perspective:

[O]ur results may contribute to how we think about the funny quirks and otherwise ‘sub-optimal’ behaviours people exhibit. Our preferences (and the behaviours they drive) are shaped by factors beyond the actual value of what we encounter in the world. Our preferences take root, in part, because of the way our brain is wired – they reflect our own biological constraints as much as they reflect anything of ‘value’ in the real world.

My Choice is Better!

My souvenir key chain is better than the one you gave me because I picked it out.  It is better because my brain feedback loop rewarded me, and because I am genetically primed to value my choice.

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