The Marshmallow Test: Understanding Self-control and How To Master It

by Walter Mischel

This is how Laibson explains his procrastination: He can exercise today (his effort cost is –6) to gain delayed health benefits (for him a future value of +8). The net benefit of exercising today for someone with his present bias is (–6 + ½ [8] = –2). In this equation, the future value of +8 was halved because of the automatic discounting of the future, making –2 the net benefit of his exercising today. In contrast, exercising tomorrow has a delayed effort cost of –6 and a delayed benefit of +8, both of which are halved because they are in the future (½ [–6 + 8] = +1). For Laibson the resulting net value for putting off going to the gym is +1, which is better than the –2 net value for exercising today. Consequently, he is rarely at the gym.

Why tomorrow never comes to the gym.