Lori, a mid-30s sales professional, took part in a clinical study on metabolic medicine that I was directing. She was one of several hundred people trying a program to lose weight and improve their health. As I sat down to interview her, I could tell she had a positive report to share. 

“Wow, I’m having such a great time! We are learning a ton about what to eat and when and how—I never knew how to do it right, ya know? I am trying out a bunch of new methods,” she gushed. I instantly felt pleased that this course was working—it was helping people—but then, she threw me right out of my self-satisfaction.

“But,” she paused, “what I don’t get is,” hand on her heart, she drew in a breath,
“I know what I should do—I just don’t know why I don’t do it!”

In one pithy sentence, Lori articulated one of the most significant and vexing questions in all of healthcare: a question that is only now answerable through recent discoveries. 

Over the past several years, a confluence of psychological, behavioral, and neuroscience studies have shed new light into human behavior. We have learned more about the brain in the past five years than in the previous 5,000 years! A new genre of brain-based books has emerged, translating this new body of science into insights on what we do and why. 

Nobel Prize-winner Daniel Kahneman’s recent book, Thinking Fast and Slow, offers an especially enlightening exploration of the gap between what people know they should do and what they actually do. Sure, Kahneman details a mountain of evidence showing how the brain’s System 1 (fast, short-cutting) and System 2 (slow, methodical) thinking work. He goes on to demonstrate that human brains are fraught with so many assumptions and biases that our subjective version of reality compared to objective, measurable reality is way off.  But what Kahneman’s book really does, is provide the answer to Lori’s question.

As a shortcut, when I teach workshops on this, I like to rename System 1 the “fast brain” and System 2 the “slow brain”.  The fast brain roughly equates to the unconscious mind. More important to Lori’s question, the fast brain also drives 95% of behavior. Examples of this include heuristics, or mental short cuts, like the order in which you brush your teeth (because, if you notice, you do it the same way every time) or travel home from work. These thoughtless, energy-efficient routines help you save your energy for the important stuff like planning a vacation or helping with your child’s math homework. 

That’s where the slow brain comes in. Anytime the brow furrows in deep thought, whether creating a presentation or doing taxes, the slow brain is in charge. For example, as Lori sits through the program on how to eat right, her slow brain is taking copious notes and making elaborate plans to implement all of the amazing information. Her slow brain is whom I interviewed that day—the one who noticed the gap between knowing what she should do and what she didn’t do.  

As insightful as the slow brain can be, research shows that the fast brain easily dominates it. Indeed, scores of experiments show that the second the slow brain is distracted—with tasks, stress, or lack of sleep—the fast brain takes over. If you ask someone to memorize a long number while offering them a selection of healthy or unhealthy treats, for example, they will more often choose the cake over fruit. Conversely, if people are asked to resist eating the cake, they will more easily give up on the memorization. Our slow brain has only so much capacity; and when it’s tied up with cerebral tasks, or just plain spent for the day, the fast brain steps in to help. Trouble is, the fast brain acts before it thinks. 

For Lori, and for all of us, the answer to the question of why we don’t do what we know we should lies in what I call the “fast brain-slow brain gap”. We all have a naturally existing asynchrony, or time lag, between what we know we should do (slow brain) and what we actually do (most of the time the fast brain). This means that the cookie is going down our gullet BEFORE we remember, “oh yeah, I didn’t want to eat that!” Lori’s slow brain, inspired by the new information she had learned in the metabolic medicine program, set a clear intention to eat better. But her fast brain still runs the show: the second her slow-brain attention is diverted by, say, reading a spreadsheet at work, the fast brain inserts cookie-into-mouth. D’oh!


Well, now that we know it is a timing thing, we can solve it with timing.  Here are three potential fixes for the fast brain-slow brain gap.

1. Slow Down
Stress, lack of sleep, & frenetic multi-tasking all favor the fast brain kicking in and taking over for the depleted slow brain. Making things slow, like freezing treats so you have to think before you eat them, gives your slow brain a chance to remind you what you should do. Generally, this means creating “friction” with obstacles, like hard to open storage containers or using chopsticks, that force you to slow down when you forget to do it yourself. 

2. Routinize
Steve Jobs notoriously wore the same type of outfit everyday. By making certain daily activities—getting dressed, for example—into a thoughtless, fast-brain routine, we save our slow brain energy for decisions and willpower that are in limited daily supply. Another successful habit: make and freeze your healthy meals for the week on Sunday so you don’t have to worry about meal planning at a moment of weakness when you are commuting home driving down a row of fast food restaurants.

3. Freshen triggers
We get bored of and ignore the slow brain reminders and triggers we set for ourselves, like old posted notes on the fridge. Our slow, conscious brain “desensitizes” to such monotony so it can spend its time on more pressing matters. For example, you probably are not feeling the clothes on your body right now because your brain ignored that sensation shortly after you put them on this morning. This slow brain trigger “blindness” turns control over to the fast brain, which has its own set of self-triggers for immediate gratification like pounding a bag of chips to reduce stress. To combat this, we must constantly refresh our triggers by trying different ways to get our own attention. Every trigger we set will eventually end up in our blind spot so this is an ongoing project. 

At the very least you now know why you know what you should do, but don’t do it. More importantly, this means that you are not bad or lazy or any other negative label we may put on ourselves when this happens. It means that you are a human, living in a world that demands way too many decisions for your slow brain and delivers way too many temptations for your impulsive fast brain. Hopefully, once you watch this pattern play out using this new point-of-view, you can try one or more of the fixes to resolve your own fast brain-slow brain gap.