Our Limited Capacity to Decide

With over 30,000 words done on my manuscript and about halfway plowing through the outline, the thesis of the book has become ever more clear. Here’s the essential. question about decision making from the point of view of neuroscience:

The ability of our brain’s executive function to make decisions is limited not only by the model it creates out of experience , but by the decisions made by brain systems that are inaccessible to awareness or executive control. We then can ask : How do you make better decisions when agency is so limited?

This morning I drafted a few paragraphs about eating that seemed to encapsulate much of the argument and seemed worth sharing here. I think it provides a little idea of the style and approach I’m taking in a longer form.

Recognize this? Your visual system will make a perceptual decision.

Embodied cognition

We’re on the subject of what has been called “the embodied mind”1. The brain is the body’s regulator of behavior of all kind including not only attention and voluntary movement but every regulatory system in the body that keeps us alive and healthy. There’s no line between “mind” and “body”, so our experience has to include input from those systems and our behavior has to be adjusted to take care of them appropriately without involvement of the executive network in the cerebral cortex.

For example, while I can’t control my heart rate directly, the feeling of my heart pounding is an important aspect of the world. My internal model of the world needs to account for whether it’s pounding because I’m sprinting in a friendly competition on my bike in a group ride or whether I’m finishing a high stakes race or whether I’m angry with and/or afraid the driver of the car that just side swiped me and who’s continuing to threaten me2. There’s context to heart rate that important in the bigger world model beyond regulation of the cardiovascular system.

The exquisite control of appetite

And so too with appetite. When I was in medical school, they had just introduced lectures on nutrition into the curriculum. There was one fact I took away from the lectures that I think about very frequently. Now you have to understand that the two families that owned the Coca Cola Company (the Candlers and then in 1919 the Woodruffs) have been major benefactors of Emory University, where I got my MD, PhD training.3

A 12 oz can of Coke has 140 calories. If you decided to add a can of coke a day to your daily diet, perhaps with lunch at the campus cafeteria, that would be 365 cans of Coke or 51,100 extra calories a year. Over a decade, more than half a million additional calories from that can of Coke. We know that there are 3500 calories in a pound of body fat. So that half million extra calories would add 146 extra pounds. Drink that can of Coke for a few decades and you’ll be hundreds of pounds overweight. Looked at another way, the average caloric intake for a man in the US is 2500 calories per day. That can of Coke that caused so much theoretical havoc is only 5.6% of daily caloric intake. For most of us with relatively stable body weight year by year, that means that our average daily intake of calories is regulated down to single digit percentage points! Not only that, but the great difficulty that we find with dieting and the empiric data showing that diets don’t work for most, demonstrates that consciously trying to regulate caloric intake is almost impossible over the long term.

Some of the ability to maintain stable body weight is due to cellular metabolic control regulating basal metabolic rate, the burning of calories at rest. But most of it is behavioral- how active we are choosing to sleep, sit or move around. And of course what and how much we eat. We are no more in control of eating than we are of breathing or respiratory rate or blood pressure.

A complex set of signals exchanged between the body’s fat stores, the gastrointestinal tract, the endocrine system and the brain allows hormones and levels of blood nutrients (sugar, amino acids, fats) to trigger food acquisition and consumption. We’re really good at knowning how much to eat. We’re fully in charge yet not aware of the expertise we have implicitly and not in any kind of long term control of it. Within a few percentage points, every day year after year. Despite the best efforts of our executive network to influence body weight.


  1. The Stanford Encyclopedia of Philosophy makes the historical attribution of embodied cogntion to a short list of authors including George Lakoff and Andy Clark. Their books have been important influences on me in formulating the abstract world of thought as metaphor in the brain’s model of the real world 

  2. Sadly confrontations with motorists is all too common out there on the bike 

  3. In fact my father, who had been a Pepsi drinker all his life switched to Coke after I was accepted to the Medical Scientist Training Program there to show his gratitude. It was a program with full scholarship and stipend after all. 

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