“Self-Control Relies on Glucose as a Limited Energy Source: Willpower Is More Than a Metaphor” is an interesting research published in 2007 by by Matthew T. Gailliot, Roy F. Baumeister, C. Nathan DeWall, Jon K. Maner, E. Ashby Plant, Dianne M. Tice, and Lauren E. Brewer, Brandon J. Schmeichel.
As indicated in their abstract, “their work suggests that self-control relies on glucose as a limited energy source. Laboratory tests of self-control (i.e., the Stroop task, thought suppression, emotion regulation, attention control) and of social behaviors (i.e., helping behavior, coping with thoughts of death, stifling prejudice during an interracial interaction) showed that (a) acts of self-control reduced blood glucose levels, (b) low levels of blood glucose after an initial self-control task predicted poor performance on a subsequent self-control task, and (c) initial acts of self-control impaired performance on subsequent self-control tasks, but consuming a glucose drink eliminated these impairments. Self-control requires a certain amount of glucose to operate unimpaired. A single act of self-control causes glucose to drop below optimal levels, thereby impairing subsequent attempts at self-control”.
Please consider that consuming sugar is not the only way to increase blood glucose levels: eating protein or complex carbohydrates offers better long-term results.
In their concluding remarks, it is stated that “It has long been known that action consumes energy. More recent evidence has indicated that some brain and cognitive processes likewise consume substantial amounts of energy—indeed, some far more than others. The “last-in, first-out rule” states that cognitive abilities that developed last ontogenetically are the first to become impaired when cognitive and physiological resources are compromised. Self-control, as a relatively advanced human capacity , was probably one of the last to develop and hence may be one of the first to suffer impairments when resources are inadequate. The present findings suggest that relatively small acts of self-control are sufficient to deplete the available supply of glucose, thereby impairing the control of thought and behavior, at least until the body can retrieve more glucose from its stores or ingest more calories. More generally, the body’s variable ability to mobilize glucose may be an important determinant of people’s capacity to live up to their ideals, pursue their goals, and realize their virtues”.
The research is available on: http://tinyurl.com/38ktkws
We also provide a selection of comments on the research. Quoting from http://neuroanthropology.net
“Galliott et al. published a 2007 article entitled “Self Control Relies on Glucose as an Energy Source: Willpower Is More Than Self Control”. Recently Vaughan at Mind Hacks and Dave at Cognitive Daily have taken up the topic with some creative posts. Vaughan writes that Resisting Temptation Is Energy Intensive, focusing on the role of attention and the prefrontal cortices. Dave posts on Practicing Self-Control Takes Real Energy, and includes a recreation of the research procedure (with video) and an informative summary. I also mentioned some of this research in a previous post on Willpower as Mental Muscle.
Diets are often marked by periods of effortful weight loss, followed by a slide back, where weight is regained. That pattern is not simply a matter of mind over matter, of willpower so we can match a cultural and cognitive ideal. It’s hard for people to maintain sustained mental efforts, it costs energy, and there’s little evolutionary reason to expect everybody’s brains to suddenly begin cooperating with what our culture tells us we should be able to do.”
Quoting from http://scienceblogs.com/cognitivedaily/2008/03/practicing_selfcontrol_consume.php
“Research led by Roy Baumeister has found that people who’ve resisted eating cookies gave up sooner on a task requiring persistence compared to those who succumbed to temptation and ate the cookies. Other research has associated low blood glucose levels with poor performance on the Stroop task — another task that requires people to avoid reading. Is it literally true that the sugar in our blood fuels our ability to control our impulses?
Matthew Gailliot, along with Baumeister and six other researchers, asked 103 psychology students to fast for three hours before watching a video like the one I showed above. Half the students were told to ignore the words, while the rest weren’t required to exercise any self-control. Blood glucose levels were measured before and after this task. The students exercising self-control had significantly lower glucose levels after watching the movie, while the other students did not. In another experiment, students performed the Stroop task after watching the movie. The students who had to resist reading the words performed significantly worse on the Stroop task; their lower blood glucose levels after watching the movie and avoiding reading seemed to impair performance.
In another experiment, a new group of 62 students watched the movie, again divided into groups who watched normally or controlled their attention by avoiding reading. Then everyone was offered a glass of Kool-aid lemonade. Half the lemonade was sweetened with sugar, while half was sweetened with Splenda, which does not affect blood glucose levels. Since glucose takes about 10 minutes to be absorbed by the brain, everyone was given a 10-minute distractor task, then given an 80-item Stroop task.
when the students consumed glucose, they performed just as well on the Stroop task, whether or not they had had to exercise self-control while watching the movie. But students who didn’t consume any glucose performed significantly worse on the Stroop test.
Gaillot’s team repeated these experiments several times, with tasks ranging from avoiding displays of racial prejudice to dealing with thoughts about death. In each case, the results supported the idea that self-control literally relies on glucose. When blood glucose is depleted, we’re less able to exert self-control. The researchers say that the brain has a limited reserve amount of glucose, which allows us to handle the initial task demanding self control, whether it be watching a movie without reading accompanying text, or avoiding fattening snacks. Once that glucose supply is depleted, self control becomes much more difficult, across an array of different tasks.”