Radishes, Cookies And Willpower

In the mid 90’s researchers from Case Western Reserve University conducted an experiment to investigate the effects of willpower depletion. In an amusing (yet somewhat mean) experiment 67 participants were invited to take part in a taste perception study and arrived at a laboratory to the smell of freshly baked chocolate cookies wafting through the air.

Formalities done each participant was assigned to a group and sat in front of two plates of food. One plate was packed with delicious cookies, the second plate was piled high with rather less appealing radishes. This is where it got interesting. Group 1 was told they could eat the cookies but not the radishes. Group 2 was told they could eat the radishes but not the cookies.

With the rules in place, the experimenters vanished behind a one-way mirror to watch the outcome. To their credit the radish group stuck to the task and despite longing glances they managed to resist eating the freshly baked goods. The cookie group on the other hand seemed to have no-such problem resisting the radishes, no surprise there.

Eventually the experimenters reemerged and told the participants they would need to wait 15 minutes or so to allow the sensory memory of the food to fade and to kill the time could they help the researchers ascertain whether college students differed from high school students in their problem-solving ability. Whilst dressed up to be fairly inconsequential this was actually the crux of the experiment. The researchers left the participants with a problem-solving task and the following instructions:

  • You can take as much time and as many trials as you want
  • You will not be judged on the number of trials or the time you take
  • You will be judged on whether or not you finish the task
  • If you wish to stop before you finish, ring the bell on the table

The task (tracing a geometric shape without retracing lines or removing pen from paper) was in-fact impossible to solve. Rather than test their problem-solving ability the researchers were keen to see how long the two groups would stick to the task before raising the proverbial white flag.


The radish group who had been forced to resist the cookies gave up approximately 10 minutes (over 50%) before the cookie group and attempted the puzzle approximately 15 less times. In essence, by resisting the cookies they had drained their willpower thus reducing the amount of effort and focus they could commit to solving the puzzle. This suggests that willpower, rather like a muscle needs time to recover between bouts of effort or else its effectiveness rapidly declines.


Applying this idea to our everyday lives can have far-reaching implications but lets narrow it down to two scenarios we can all relate to.

Exercise - If there is one magic ingredient to getting fitter and stronger, it is consistency. You don’t need to exercise hard everyday (far from) but neither can you miss workout after workout. If you see exercise as a chore then schedule your workouts earlier in the day before other stressors, decisions and temptations have taken their toll on your willpower. In short, structure your day in a manner which positively shifts the odds of you consistently sticking to your routine. For many this means earlier workouts.

Healthy Food Choices - Along with skipped workouts another area many of us commonly struggle with is the excessive consumption of convenience foods which are purposefully designed to light up all the reward sensors in our brain. If this sounds familiar then eliminate willpower from the equation by emptying your cupboards of all the junk. It sounds so simple but now these hyper-palatable foods cannot chip away at your willpower leaving you vulnerable to a binge.


You can’t rely on willpower alone to make healthier decisions. If you struggle with missed workouts or resisting certain foods then change your schedule or manipulate your environment in a manner which reduces your reliance on willpower - a resource which is not always going to be fresh and strong when you need it the most.


  • Baumeister, R, et al (1998), Ego Depletion: Is The Active Self A Limited Resource? Journal of Personality and Social Psychology, Vol. 74, No. 5, 1252-1265