Study indicates willpower not depleted by use nor replenished by food

Glucose C6H12O6. Credit: Wikipedia.

(Medical Xpress)—A team composed of researchers from Stanford University and the University of Zurich has found evidence that suggests willpower is not depleted by use, nor replenished by glucose. In their paper, published in Proceedings of the National Academy of Sciences, the researchers describe their experiments which indicate that a person's belief that willpower can be depleted has more bearing on their own perception of willpower.

For people, is generally considered to be the ability to not do something that is desired, or to continue doing something that is not desired for a greater good. Prior research has suggested that willpower, because it requires work, can become depleted if more brain food (glucose) isn't provided to the brain. In this new effort, the researchers contradict that theory and suggest that a person's belief in whether their own willpower can be reduced if their brains don't receive reinforcement has more to do with their own individual level of willpower.

The researchers ran three experiments. In the first, a group of volunteers was asked to forgo eating or drinking for two hours prior to the experiment. The first part of the experiment involved quizzing the volunteers on their beliefs about willpower. That was followed by giving all of the volunteers a sweetened beverage—half received a drink with sugar, and half received a drink with a sugar substitute. Following that, each of the volunteers was asked to take tests that measure self-control and brain acuity. In analyzing the results, the researchers found that those volunteers who believed they needed a sugar drink to maintain willpower performed poorly if given an artificially sweetened drink—those who believed willpower was unlimited performed equally well regardless of the consumed.

In the second experiment, the researchers attempted to nudge the volunteers' views about willpower by manipulating the questionnaire prior to repeating the same exercise. This time around, the researchers found that those volunteers who had been led to believe willpower requires rejuvenating tended to do poorly on the second part of the experiment if they consumed an artificially sweetened drink, while those who had not needed no rejuvenation.

In the third experiment, the researchers ran the same exercise as the first experiment but didn't ask the volunteers to fast prior to the experiment. Also, they lied to the regarding whether their drink was artificially sweetened or not. Analysis showed that those who believed willpower needed rejuvenation lagged when given an artificially sweetened drink regardless of whether they knew what they were getting.

These experiments show, the researchers report, that willpower is dependent on an individual's belief in their need for rejuvenation, rather than a physical need to feed the brain more to keep their willpower strong.

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More information: Beliefs about willpower determine the impact of glucose on self-control, PNAS, Published online before print August 19, 2013, DOI: 10.1073/pnas.1313475110

Past research found that the ingestion of glucose can enhance self-control. It has been widely assumed that basic physiological processes underlie this effect. We hypothesized that the effect of glucose also depends on people's theories about willpower. Three experiments, both measuring (experiment 1) and manipulating (experiments 2 and 3) theories about willpower, showed that, following a demanding task, only people who view willpower as limited and easily depleted (a limited resource theory) exhibited improved self-control after sugar consumption. In contrast, people who view willpower as plentiful (a nonlimited resource theory) showed no benefits from glucose—they exhibited high levels of self-control performance with or without sugar boosts. Additionally, creating beliefs about glucose ingestion (experiment 3) did not have the same effect as ingesting glucose for those with a limited resource theory. We suggest that the belief that willpower is limited sensitizes people to cues about their available resources including physiological cues, making them dependent on glucose boosts for high self-control performance.

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Aug 20, 2013
The headline is not suppoted by the text of the press release. Headline "Study indicates willpower not depleted by use nor replenished by food". Suppose that the willpower of different people depends differently on their nutritional state in their daily life (contrary to the hypothesis of the paper). That is some lose willpower quickly when sugar intake is diminished. Others find that their willpower is maintained when sugar intake is diminshed. The first group would then tend to believe that willpower depends on sugar intake -- given their exprience with their own body in daily life. Conversely, the second group would tend to believe that willpower did not depend on sugar intake. This separation would nicely explain the results of experiments 1 and 3 and might be consistent with experiment 2. Thus the subjects beliefs would not be causal but would be an accurate reflection of some underlying physico-psychological reality.

Correlation is not causality.

Aug 20, 2013
It's pretty obvious to anyone who goes into a grocery store hungry that food definitely affects willpower.

Aug 20, 2013
Psychologists are fond of re-discovering the self help seminar effect and asking for more tax dollars to go off and re-discover it yet again, to the delight of magazine editors. This is amusingly similar to late 1950s psychologists who tried to study hallucinogens by blinking lights at human subjects in sterile hospitals as they jotted down notes on clipboards. Bad trip alert! Here they remove real world variables and ignore the obvious fact that different people's "belief" about willpower are reflections of their own physiotype, so those who "believe" that willpower is helped by sugar are those whose brains are somewhat starved of the stuff in the first place. This study comes from a field of science that abandoned penis envy to spend decades treating real therapy clients using the theory that humans were accurately modeled by pigeons getting shocked in little cages. Nowadays though, they have indeed stolen the thunder of self help gurus, but they call it CBT and REBT. Cads!

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