I used to think that willpower was a never-ending pit of untapped resolve. As you practiced foregoing that extra glass of Chardonnay on New Year's or avoiding the leftover holiday desserts, your access to that willpower would grow larger and larger until finally you could just be one big ball of stubborn resolve. At least, that's what I desperately believed every time New Years Eve rolled around, writing out a list of my resolutions and promising to actually follow through with them this year.
I couldn't have been more wrong. Willpower is a limited resource, and it only decreases with stress. Willpower comes from the prefrontal cortex, an area of the brain right behind your forehead. The prefrontal cortex is also responsible for other important tasks, such as abstract thoughts and short term memories and tasks. Simply put, there's just not enough prefrontal cortex to go around.
Baba Shiv, a researcher at Stanford University, gathered
undergraduates and divided them into two groups. One group was tasked with remembering a two digit number, the other a seven digit number. Each participant was then led into another room and given an option of snack: a slice of chocolate cake or a bowl of fruit salad. The study was meant to test the resolve of students when faced with a tasty treat while their brain is preoccupied with a memory task.
The seven digit students were twice as likely to go for the cake than those students that were asked to remember the two digit number. According to Professor Shiv, it's because those extra numbers took up enough space to produce a "cognitive load." Essentially, willpower was compromised from having to remember a larger number; the prefrontal
cortex was overloaded, and all New Years resolutions are out the window.
In a related study, Mark Muraven at the University of Albany asked participants to write their thoughts down for five minutes - while not thinking of a white elephant, a more difficult task than you may think (go ahead, try it). Afterwards, the subjects were asked to take a beer taste test, then drive a car. The students who were asked to not think of white elephants consumed a significantly larger amount of beer than the control group. This suggests that the white elephant task took a toll on the prefrontal cortex, and when given the choice to drink, they indulged, even though they knew they would be driving a car afterwards. You might say that white elephants result in pink elephants!
Source: Science Blogs