Reason #99 to Never Enter the Grocery Store Without Your Grocery List

The grocery store. Fraught with pitfalls. Even if you eschew the inner aisles and their processed pseudofoods in favor of the whole foods found around the outside of the store, you must still contend with the bakery and its temptations.


This little thing? It’s the least of my worries in the bakery.

This is why all the experts advise us to come with shopping list in hand. Stick to the list! No inpulse purchases. It’s good advice, but the list serves another purpose as well. It turns out that we’re more likely to make emotional, impulsive choices when our rational brains are busy.

Sign that indicates a public restroom is in use

Rational brain: “Sorry, I’m busy. Come back later.”

In a recent RadioLab broadcast , the hosts discuss a fascinating study by Baba Shiv at the Stanford School of Business. It’s worth listening to – the first ten minutes are entertainment gold, if you ask me – but if you can’t, here are the CliffsNotes:

It seems that the brain is anatomically organized into different systems…. You have a rational, deliberative system … and an emotional, unconscious system… These two systems are often at war.

In the study, participants were placed in a room and asked to memorize a number. Some participants received easy numbers. Twelve, or example. Some participants received longer, seven-digit numbers.

We already know that the average human brain can store only seven numbers, plus or minus two, in short-term memory, and we have to work pretty hard to keep those numbers at the forefront, to make sure they don’t slip away into the ether.

The interesting thing, though, is not that our brains can store only seven numbers, plus or minus two.

The interesting thing is what happens to our decision-making powers when you try and get more than seven [digits] in your head.

After being given as much time as desired to memorize their numbers, particiapnts were asked to walk into another room and recite that number. On the way to that second room is where it gets interesting. Someone stopped participants in the hallway and offered them a snack, just to say thanks for helping with the study.

Once choice was a healthy bowl of fruit salad, and the other choice was a big, fat slice of chocolate cake. Mmmmmmm.

The people with two digits in their head almost always choose the fruit, whereas the people with seven digits in their head almost always choose the cake!

Now, obviously, not everyone watches calories the way we do, so they might not find cake vs fruit to be an agonizing decision. But even so, most people do recognize that fruit is a healthier choice and try to make the healthier choice more often than not. Yet in the study, the people with seven digits preferred cake by 20 or 30 percentage points. That’s too marked to ignore.

With seven digits in your head, the rational brain has too much to keep track of. As the hosts point out, it not surprising that emotion might sometimes win over rational thinking. It’s how easily it wins. “Seven digits is all it takes.”

Which takes us back to our grocery list. If you’re in the store trying to remember twenty-some different items, your rational brain is way too busy to help you fend off your emotional brain, the one that wants the cake, chips, and soda. So do yourself a favor and always make a list.

Can you think of other situations where your rational brain is occupied, making you more vulnerable to emotional or absent-minded eating?


  1. I lived my life for years with my emotional side completely overrunning my rational side. I wish I could blame it on being busy learning things, but instead I just pushed rational thought aside when it came to healthy food choices.

    This was a fascinating study – thanks for sharing.

    • I can really identify with that, Diane: “…pushed rational thought aside.” I certainly can’t blame my weight on being busy learning things, either!

      I did fall into a bad habit over the winter where I stopped at the gas station for breakfast after dropping my son off at school. I made a conscious decision one morning on the way to school that I was not going to stop for that unhealthy breakfast. Twenty minutes later I was tooling down the highway eating a bacon, egg and cheese bagel. I was distracted with thoughts about work and stopped at the gas station out of habit! This study reminded my a little of that experience.

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