Our bodies are not just slaves to our minds. They also provide feedback telling us what we're thinking. And they can be hacked. Eye drops feel like tears and make us sad. Extending your middle finger (even if you're not consciously flipping anyone off) automatically raises your level of ire. (See here for several related studies.) Now new research in press at the Journal of Consumer Research [pdf] finds that you can increase willpower merely by tightening your muscles.
We associate flexed muscles with endurance and striving for goals. Physical exertion is usually an effect of these things but Iris Hung and Aparna Labroo wanted to know if it could also be a cause.
In one experiment, people decided whether to donate money to a Haiti relief effort. Half the subjects gripped a pen tightly against their palm, and half held a pen loosely. The grippers fought selfishness better than the control crowd and more of them donated. In another experiment, people who gripped a pen tightly held their other hand in painful ice water for a longer period of time (purportedly as a test of good circulation).
In a third experiment, subjects tasted a yucky "health tonic" (actually 10 parts water, one part vinegar). People asked to hold their heels off the floor and clench their calves drank more of it. In a fourth, students holding a pen woven through spread fingers purchased healthier snacks at a snack bar than a control group did. And in a fifth, subjects flexing their biceps said they'd be less likely to break their diet and eat a slice of chocolate cake.
The researchers showed that tightening muscles doesn't just increase pain tolerance. It boosts willpower; the interventions only worked if people desired the purported effects of what they were enduring. (For example, only people primed with sentences like "fitness is a virtue" drank more of the "health tonic" when clenching.) According to the researchers, "Steely muscles can lead to a steely resolve."
There's other work by Roy Baumeister and others showing that willpower is a limited resource and it can be taxed just like a muscle. So why didn't those effects show up here? Why didn't working biceps weaken restraint? It did—if subjects flexed before being tempted by cake. They'd used up their self-control. But if they encountered cake while showing off their guns they were still in man-of-steel mode and said no.
This is why I always tuck a ThighMaster under the table when the desert menu arrives.