The Frontal Cortex

Choosing is Hard

Over at Mind Matters, the expert blog I curate at Scientific American, we’re currently featuring a really interesting article by On Amir on the cognitive cost of making decisions:

For instance, it’s long been recognized that strenuous cognitive tasks–such as taking the SAT–can make it harder to focus later on. But recent results suggests that these taxing mental activities may be much broader in scope-and may even involve the very common activity of making choices itself. In a series of experiments and field studies, University of Minnesota psychologist Kathleen Vohs and colleagues repeatedly demonstrate that the mere act of making a selection may deplete executive resources. For example, in one study the researchers found that participants who made more choices in a mall were less likely to persist and do well in solving simple algebra problems. In another task in the same study, students who had to mark preferences about the courses they would take to satisfy their degree requirements were much more likely to procrastinate on preparing for an important test. Instead of studying, these “tired” minds engaged in distracting leisure activities.

Why is making a determination so taxing? Evidence implicates two important components: commitment and tradeoff resolution. The first is predicated on the notion that committing to a given course requires switching from a state of deliberation to one of implementation. In other words, you have to make a transition from thinking about options to actually following through on a decision. This switch, according to Vohs, requires executive resources. In a parallel investigation, Yale University professor Nathan Novemsky and his colleagues suggest that the mere act of resolving tradeoffs may be depleting. For example, in one study, the scientists show that people who had to rate the attractiveness of different options were much less depleted than those who had to actually make choices between the very same options.

Another cool study on this theme comes from Roy Baumeister’s lab at FSU. The experiment began with a large group of undergraduates performing a mentally taxing task, which involved watching a video while ignoring the text of random words that was scrolling by at the bottom of the screen. (It takes conscious effort to not pay attention to such “salient stimuli”.) Then, the researchers offered the students some lemonade. Half of the students were given lemonade made with real sugar, while the other half got lemonade made with a sugar substitute. (The fake sugar tastes sweet but contains no calories.) After giving the glucose time to enter the bloodstream and perfuse the brain – this only takes ten to fifteen minutes – Baumeister had the students make a decision about apartments. It turned out that students given a drink without real sugar were significantly more likely to rely on instinct and intuition when choosing a place to live, even if it led them to choose the wrong place. The reason, according to Baumeister, is that the brains of these students were simply too exhausted to think. They needed a restorative sugar fix, but all they got was Splenda. This research can also help explain why we get “cranky” when we’re hungry and tired: the brain is less able to suppress the negative emotions sparked by small annoyances.

The moral of all this work is that the part of the brain devoted to deliberate analysis and cognitive processing (some circuitry centered in the prefrontal cortex) is remarkably feeble and fragile.


  1. #1 F. Phillips
    July 23, 2008

    Interest in creativity made the SciAm article and your blog special. You’ve partially answered my two questions: the effect of diet on executive function and not as well, restorative actions we can take to get back on track such as humor, change of focus… I’d appreciate your further comments and suggestions. Thank you. FP

  2. #2 Pierce R. Butler
    July 23, 2008

    So why does “The Decider” in the White House always look so chipper?

  3. #3 TomK
    July 23, 2008

    If you are studying executive function you should read David Allen’s Getting Things Done.

    It really sounds to me like you are studying the neural correlates of David Allen’s psychological arguments about why GTD is an effective system. It seems to me an intrepid young neuroscientist should be able to map some of Allen’s claims about how the brain organizes information onto this stuff.

    It’s not that the reasoning centers of the brain are weak, it’s that there is a high cost involved with switching gears. Changing from using logic to decide and the execution is energy intensive. GTD is basically a hack that separates out using logic to decide what to do and doing it. These experiments seem to me like justification for Allen’s GTD system, and his arguments about why that system is helpful at reducing mental stress and exhaustion.

  4. #4 TobyF
    July 23, 2008

    Naw, the moral is: Sugar good.
    Now let’s try that experiment with bacon.

  5. #5 Richard Eis
    July 24, 2008

    I wonder if there is also extra baggage in the form of worry over a possibly wrong decision. Just becuase a decision is made doesn’t mean the brain stops thinking about it.

  6. #6 phisrow
    July 24, 2008

    Well, these results definitely don’t make me even slightly nervous about the proliferation of those little scrolling text tickers at the bottom of TV broadcasts. After all, instinct and intuition should be enough for any decision!

    In seriousness, though, I wonder if the extraordinary options for bombarding oneself with stimuli, along with a fad for multitasking, are causing such effects on a fairly broad basis. I’d be an unpleasant irony if our rush to aggregate extra data sources led to lousy decision making.

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