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Mind

How the Need to Pee Helps (and Hurts) Decision Making

InkfishBy Elizabeth PrestonOctober 12, 2011 4:12 AM

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The Ig Nobel awards are an annual, tongue-in-cheek version of their namesake, recognizing researchers for ridiculous-sounding papers ("How to Procrastinate and Still Get Things Done") and obscure areas of study (why do certain Australian beetles continuously attempt to mate with discarded beer bottles, even as ants chew off their genitalia?). Sometimes, the awards editorialize on the year's news: Erroneous doomsday predictor Harold Camping won this year's mathematics prize "for teaching the world to be careful when making mathematical assumptions and calculations".

The best Ig Nobel winners, though, start with a silly question and end up with an interesting answer. This year, the prize in medicine went to two different research groups pursuing the same burning question: What happens to our cognitive abilities when we really, really have to pee?

One paper examined subjects' speed in a memory-based test. The adult subjects watched playing cards flipping over on a screen and had to press keys to indicate whether the cards were red or black and whether each card matched the previous one. Oh, and every 15 minutes they had to drink another 250 ml of water.

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The researchers repeatedly asked subjects to rate their urge to urinate on a scale ranging from "not at all" to "the most I have ever felt in my life." It took an average of two hours and 20 minutes, and a little over two Nalgenes' worth of water, for subjects to reach the desperate end of the scale. At that point, they completed the computer task a final time before relieving themselves.

Though subjects' accuracy on the simple task never decreased, those who most urgently had to pee were slower to decide whether a card matched the one before it. There were only eight people in this study, so results should be interpreted with caution. But the researchers say that the slowed reaction time they saw was comparable to the effect of pulling an all-nighter, or having a BAC of .05%. If you're on the road and need to go, maybe you shouldn't wait too long to pull over.

The second Ig Nobel winner used larger study groups and asked how the need to pee affects our impulse control abilities. The researchers started with a classic Stroop test, in which color words are printed in contradictory ink hues:

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It's easy for us to read the list aloud, but harder to go through the list and name the color of each word. That's because we have to suppress our first impulse, which is to just read what's there. The researchers gave subjects a Stroop test, then asked afterward how badly their subjects had to pee. All the subjects performed equally when reading the words. But when it came to naming the color of each word, subjects who reported a greater need to urinate were faster.

The researchers say that inhibiting our motor reflexes--in this case, inhibiting the urge to pee--helps us to simultaneously inhibit other urges. They tested their hypothesis in a few other ways. In one experiment, they first made sure half their subjects needed to pee by giving them 700 ml of water and waiting 45 minutes. Then subjects answered a series of questions about rewards: for example, would you rather have $16 tomorrow, or $30 in five weeks? Full-bladdered subjects were more likely to choose a larger reward in the future. The result was the same when, instead of drinking water, subjects filled out a word search that included a lot of terms such as "toilet" and "bladder." After being "primed" in this way, not only did subjects feel like they had to use the bathroom; they also tended to opt for the larger and more distant reward.

By happy coincidence, the name for this phenomenon is "inhibitory spillover." An effort at inhibition in one part of the brain leaks out to other areas. In this study, restraining themselves physically makes people more restrained in their decisions. Why take the smaller amount of money now, a subject reasons, when the reward will be bigger in the future? By then, maybe this burning feeling in my bladder will even be gone!

Exploring how people inhibit their impulses might teach us how to make better, or at least more forward-thinking, decisions. Should we take a small reward now, or hold out for something better? Should we accept $10 today for participation in a scientific study, or be free to use the bathroom whenever we like? The two studies seem to reach different conclusions about how the urge to "void" affects our cognitive processes, but really they're asking different questions. Taking them together, you might say that having a full bladder is a bad time to drive a car--but not such a bad time to buy one.

Lewis, M., Snyder, P., Pietrzak, R., Darby, D., Feldman, R., & Maruff, P. (2011). The effect of acute increase in urge to void on cognitive function in healthy adults Neurourology and Urodynamics, 30 (1), 183-187 DOI: 10.1002/nau.20963

Tuk, M., Trampe, D., & Warlop, L. (2011). Inhibitory Spillover: Increased Urination Urgency Facilitates Impulse Control in Unrelated Domains Psychological Science, 22 (5), 627-633 DOI: 10.1177/0956797611404901

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