Quilted Science

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New Year's Resolutions: Neural Tug-of-Wars

Successful resolutions require the brain's goal-directed systems to win the war

Lose weight. Exercise more. Eat more healthfully. 

These ever-popular New Year’s resolutions involve overwriting your current behaviors with better behaviors.  Changing any behavior can be challenging (even when it’s not January, when everyone makes resolutions). New Year’s resolutions play out as a tug-of-war between the brain’s decision-making networks.

New Year's resolutions are a tug-of-war between the brain's decision-making systems.
http://www.flickr.com/photos/toffehoff/244870160/

Caltech neuroeconomist Antonio Rangel recently proposed how to link two important but currently disparate areas of research: research on the neuroscience of decision-making and on the brain processes that keep the body fueled through feeding (homeostatic regulation).

Rangel proposes that, for eating decisions, homeostatic regulation processes influence the same brain architecture used to make other decisions like which shirt to buy or how much money to save.

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Decisions are made in the brain in multiple ways, via different networks of brain areas and with different computations that lead to a decision. 

Current thought is that there exist three brain systems that make decisions: the so-called Pavlovian, habitual, and goal-directed systems. The tug-of-war for making healthy eating decisions happens between these three decision-making systems.  Rangel explains why effective dieting is so tough: “The Pavlovian and habit systems ignore long-term consequences.  They can be inhibited, but only when the goal-directed system … detects a conflict, and inhibits the competing responses.”

The Pavlovian system is responsible for decisions you make without thinking, via hardwired pathways.  An example is mindless snacking on proximal food.

The habitual system is also responsible for decisions you make without thinking, but the underlying brain activity is different than the Pavlovian system.  An example of a habitual eating decision is having a cup of coffee at the same time each afternoon.

In humans, unlike other animals, the goal-directed system is at work in all food-related decisions. Examples of the goal-directed system at work in regulating eating decisions are following a dietary plan or keeping a food diary.

For a resolution about eating healthy to be successful, the goal-directed system must win the tug-of-war with the Pavlovian and habitual systems.

But the goal-directed system does not always win the tug-of-war.  Sometimes the Pavlovian or habitual systems override the goal-directed system, such as when we make poor food choices while under stress or cognitive load.

Because obesity rates have exploded recently in human evolutionary history, Rangel proposes that biology is not solely to blame.  He focuses on environmental variables, such as the ease of food availability and portion size.  Rangel also suggests that the same environmental factors influence homeostatic and decision-making processes alike, leading to “mistakes in decision-making” regarding food that lead to obesity.

Keeping your New Year’s resolution to eat healthier (and lose weight) is simple, at least in writing. Just make sure the goal-directed system wins the tug-of-war!  In practice though, ensuring the goal-directed system wins out is a complex undertaking due to the pressures of modern life and also because of individual differences in both decision-making and homeostatic processes.  (For an example of individual differences in homeostatic processes, think of that person you know who can eat anything without gaining weight and then think of another person you know who gains weight just by looking at food.)  

There is no guaranteed way to ensure the continued success of the goal-directed system in carrying out eating decisions.  What works for one person might not work for another; you have to figure out what works for you. Once you can keep the goal-directed system winning, new decision trajectories will be created in the habitual system.  Then, keeping that New Year’s resolution becomes easy since healthy habits are just has hard to break as unhealthy ones

Kimberlee D’Ardenne, Ph.D. is a neuroscientist by training, science writer by choice.

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