Apesar do termo científico ser volição, a expressão coloquial força de vontade parece ser muito mais acertada do que se imaginava.
Pesquisas mais atuais sugerem que há uma energia volitiva, sujeita à fadiga, e não uma simples habilidade. O experimento original - e um tanto “cruel” - era o seguinte:
In the first part of the trial, Baumeister kept the 67 study participants in a room that smelled of freshly baked chocolate cookies and then teased them further by showing them the actual treats alongside other chocolate-flavored confections. While some did get to indulge their sweet tooth, the subjects in the experimental condition, whose resolves were being tested, were asked to eat radishes instead. And they weren’t happy about it. As the scientists noted in their Journal of Personality and Social Psychology paper two years later (PDF), many of the radish-eaters “exhibit[ed] clear interest in the chocolates, to the point of looking longingly at the chocolate display and in a few cases even picking up the cookies to sniff at them.”
After the food bait-and-switch, Baumeister’s team gave the participants a second, supposedly unrelated exercise, a persistence-testing puzzle. The effect of the manipulation was immediate and undeniable. Those who ate radishes made far fewer attempts and devoted less than half the time solving the puzzle compared to the chocolate-eating participants and a control group that only joined this latter phase of the study. In other words, those who had to resist the sweets and force themselves to eat pungent vegetables could no longer find the will to fully engage in another torturous task. They were already too tired.
Ou seja, como uma força qualquer, pode ser exaurida ao fazer várias tarefas, que a seu turno podem ser mais, ou menos, dispendiosas. Um resultado muito interessante, e que abre diversas possibilidades de estudo sobre o comportamento humano.