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The Role of Glucose in Self-Control

Authors:
  • CHX Performance (London-England/Chamonix-France)

Abstract

The strength model suggests that self-control relies on a limited resource. One candidate for this resource is glucose. Counter to the proposals of the glucose hypothesis, this study argues that the resource issue is one of allocation, not of limited supply. It addresses the argument from three perspectives: the evolution of mental processes at the species level, the adaptation of these same processes at the individual level, and the physiology of glucose transport. It is argued here that the brain has both sufficient resources and resource delivery mechanisms with which to support self-control but that these resources are allocated in accordance with personal priorities. As an alternative to the limited resource model, the current study proposes a resource-allocation model of self-control and presents several testable hypotheses.
Personality and Social Psychology Review
XX(X) 1 –11
© 2011 by the Society for Personality
and Social Psychology, Inc.
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DOI: 10.1177/1088868311419817
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Article
Self-control is fundamental to human interaction and arguably,
in evolutionary terms, to human survival. In the former setting,
it enables people to behave in a manner consistent with social
norms. In the latter, it may have enabled individuals to over-
come emotional responses such as fear and anger that, although
generally adaptive, might have proved counteradaptive in cer-
tain circumstances. The failure of individuals to exert self-
control has been implicated in phenomena ranging from obe-
sity and personal debt to disease and violent crime (Muraven
& Baumeister, 2000). Self-control is therefore of interest to
many areas of social science.
Baumeister, Heatherton, and Tice (1994) identified three
distinct psychological approaches to the study of self-control.
First, traditional folk concepts such as willpower suggested
that self-control relies on a limited resource. Second, cogni-
tive models suggested that self-control is a function of factors
such as knowledge, decision making, emotion regulation,
and choice. Third, developmental approaches treated self-
control as a learned skill. Muraven, Tice, and Baumeister
(1998) tested these models in experimental studies. They hypoth-
esized that whereas a limited resource model would predict
that self-control ability would decline over repeated attempts,
cognitive and developmental models would predict no such
decline (in fact, cognitive and developmental models might
predict an improvement in self-control over time). Based on
the findings of several studies, the authors concluded that the
limited resource model best fit the evidence. The same research
team subsequently proposed the strength model, positing
that acts of self-control are “fueled” by a limited resource.
Furthermore, repeated self-control attempts deplete this reso urce
sufficiently to compromise subsequent attempts (Baumeister,
2003; Baumeister, Bratslavsky, Muraven, & Tice, 1998; Muraven
& Baumeister, 2000). These authors also proposed the term
ego depletion to describe the lack of resources resulting from
one or more attempts at self-control.
Muraven and Baumeister (2000) summarized the strength
model in five key proposals. First, self-control strength is nec-
essary for the executive component of the self. Second, this
strength is limited, in the sense that a person has finite capac-
ity for self-control. Third, all self-control operations draw on
the same resource. Fourth, the success or failure of self-control
depends on the person's level of self-control strength. Last,
self-control strength is expended in the process of self-control.
Muraven and Baumeister also made a clear distinction
between a limited resource model, such as that applied to
self-control, and a limited capacity model, such as is often
used to describe attention and working memory. This distinc-
tion was based on the proposal that although working mem-
ory appears to have a limited capacity, that capacity does not
appear to remain “depleted” after use; the full capacity of atten-
tion or working memory is available as soon as an attention
419817PSRXXX10.1177/1088868311419817Beedie
and LanePersonality and Social Psychology Review
1University of Wolverhampton, Wolverhampton, UK
Corresponding Author:
Christopher J. Beedie, School of Sport, Performing Arts, and Leisure,
University of Wolverhampton, Gorway Road, Walsall, WS13BD, UK
Email: chrisbeedie@sky.com
The Role of Glucose in Self-Control:
Another Look at the Evidence and an
Alternative Conceptualization
Christopher J. Beedie1 and Andrew M. Lane1
Abstract
The strength model suggests that self-control relies on a limited resource. One candidate for this resource is glucose. Counter
to the proposals of the glucose hypothesis, this study argues that the resource issue is one of allocation, not of limited supply.
It addresses the argument from three perspectives: the evolution of mental processes at the species level, the adaptation
of these same processes at the individual level, and the physiology of glucose transport. It is argued here that the brain has
both sufficient resources and resource delivery mechanisms with which to support self-control but that these resources are
allocated in accordance with personal priorities. As an alternative to the limited resource model, the current study proposes
a resource-allocation model of self-control and presents several testable hypotheses.
Keywords
ego depletion, evolutionary psychology, motivation, physiological adaptation
2 Personality and Social Psychology Review XX(X)
or memory task is completed. In contrast, the concept of a lim-
ited resource suggests that the resource is depleted by the
mental process and must be replenished before that process
is able to function fully again. Baumeister (2003) summarized
the work from his laboratory to that point by stating, “All our
findings suggest that it [self-control] operates like a muscle or
a well of energy. It becomes depleted through use and takes
time (and rest) to replenish itself” (p. 4).
Since 1998, almost 90 published studies have tested the
strength model and ego depletion (Hagger, Wood, Stiff, &
Chatzisarantis, 2010). The experimental method typically
adopted in this research has been the dual-task design. In this
approach, experimental participants complete two consecutive
tasks requiring self-control, whereas control participants
complete one task not requiring self-control followed by one
task that does. The hypothesis is that experimental participants
will experience greater ego depletion than controls following
the first experimental task and will therefore perform worse
than controls on the second experimental task. The majority
of the published studies support the strength model and
lend support to the second, fourth, and fifth of Muraven and
Baumeister’s (2000) proposals above. Furthermore, ego-
depletion effects have been observed in a wide range of exper-
imental tasks, including resisting the temptation to eat chocolate
(Baumeister et al., 1998, Study 1), the suppression of emotion
(Muraven et al., 1998, Study 1), the suppression of prejudice
and stereotype (Gordijn, Hindriks, Koomen, Dijksterhuis, &
van Knippenberg, 2004), and the suppression of thought (Vohs,
Baumeister, & Ciarocco, 2005, Study 5). These findings sug-
gest a common self-control resource, thereby lending support
to Muraven and Baumeister’s third proposal above. Colle ctivel y,
the findings suggest not only that self-control depends on a
limited resource, but that the same resource might underlie
self-control across a wide range of situations.
In a recent quantitative synthesis of published research
that has used the dual-task design to investigate the strength
model, Hagger et al. (2010) meta-analyzed 83 studies with 193
independent effects. The authors reported an overall effect
size of 0.62 (95% CI [0.57, 67]), suggesting a moderate to
large overall effect (Cohen, 1987). Only two of these effect
sizes were in the opposite direction to that proposed in the
strength model. Based on these findings, Hagger et al. concluded
that “the strength model is a useful explanatory system with
which to understand self-control” (p. 520) and that the find-
ings “corroborate the view that self-control draws from a sin-
gle, global resource and depletion is not an artifact of specific
spheres or tasks” (p. 515). They did, however, caution that
“further refinements may be necessary, particularly when it
comes to the identification of mechanisms” (p. 520).
The issue of what mechanism or resource underlies self-
control strength remains unanswered. It has been proposed
that the ego depletion effect might be the result of individuals
conserving their resource. For example, Muraven, Shmueli,
and Burkley (2006) reported that participants who expected
that they would undergo three self-control tasks tended to
experience greater ego depletion before the second task than
participants who believed they only had to perform two.
Alternatively, motivation has been posited as a key factor in
self-control. For example, it has been demonstrated that indi-
viduals perform better at self-control tasks when presented
with incentives (e.g., Muraven & Slessareva, 2003).
Recently, Gailliot, Baumeister, and colleagues (De Wall,
Baumeister, Gailliot, & Maner, 2008; Gailliot, Peruche,
Plant, & Baumeister, 2009; Gailliot and Baumeister, 2007;
Gailliot et al., 2007) proposed that brain glucose is the
resource that underlies self-control. Gai lliot an d Baume ister
(2007) argued, “Findings fit an energy model because they
suggest that the first act of self-control consumes or depletes
some resource, thereby impairing self-regulation on a sub-
sequent task” (p. 305). They continued, “Multiple find-
ings have indicated that acts of self-control lead to low
levels of glucose . . . there was also ample evidence that
low glucose contributes to poor self-control” (p. 319).
In support of their proposals, Gailliot and Baumeister
(2007) suggested two main hypotheses. First, “effortful, con-
trolled, or executive processes are quantitatively different from
other processes in that they require more glucose” (p. 306).
Second, “glucose can be consumed in the brain faster than it
can be replenished however, and so cerebral activities can
deplete the brain’s supply of glucose” (p. 306). In a series of
nine experimental studies, Gailliot et al. (2007) demonstrated
experimentally that acts of self-control reduced blood glucose
levels and that these low levels of blood glucose predicted
poor performance on a subsequent self-control task.1 They
also demonstrated that consuming a glucose drink eliminated
observed ego depletion effects. In investigating alternative
mechanisms, the authors stated that moods, emotions, and
arousal did not relate to the dependent variable and therefore
did not explain the link between glucose and self-control
performance.
In the 2 years following the above studies, the same research
laboratory presented further experimental data in support of
the glucose hypothesis (De Wall, Baumeister, Gailliot, &
Maner, 2008; Gailliot, Peruche, Plant, & Baumeister, 2009;
Masicampo & Baumeister, 2008). In meta-analyzing the
findings of these studies, Hagger et al. (2010) estimated the
overall effect size for glucose supplementation in self-control
to be large by Cohen’s (1987) criterion at 0.75 (95% CI
[0.48, 1.03]). Hagger et al. concluded, “Supplementing peo-
ple with glucose is associated with significantly better per-
formance on self-control tasks among depleted people relative
to controls provided with a sweet placebo” (p. 514).
Empirical support for both the strength model and the glu-
cose hypothesis is growing. The hypothesis is groundbreak-
ing and consistent with a trend toward greater interdisciplinary
overlap between psychology and related scientific disciplines
(American Psychological Association, 2010). However, we
believe that there are problems with the hypothesis, specifi-
cally, the position that glucose unavailability is a causal factor
in the impairment of self-control. Rather than contest the
Beedie and Lane 3
validity of the evidence linking blood glucose levels and
self-control as does Kurzban (2010), whose findings we
briefly review below, in the present article we question the
mechanism proposed to explain glucose depletion. We argue
that the resource issue is one of allocation, not of limited
supply. Our explanation of this process is that the human
organism is, in all but the most extreme situations or among
populations with specific health conditions, able to supply
sufficient glucose to the brain to fuel necessary mental pro-
cesses. We argue that the redirection of glucose is governed by
an appraisal of the situation in the context of available resources
and immediate individual priorities. We present three argu-
ments in support of this proposal: the first based on the evolu-
tion of mental processes at the species level, the second on
the adaptation of these same processes at the individual level,
and the third on the physiology of glucose transport.
Furthermore, we present a resource allocation model of self-
control (RAMS) that explains self-control in terms of the allo-
cation of resources in response to the perceived importance
of the task. We also propose testable hypotheses.
Evolutionary Mechanisms
at the Species Level
Evolutionary theory suggests that each characteristic of a spe-
cies is present in a certain quantity because past members
of the species possessing that characteristic in that quantity
benefited in survival or mating terms over those that did not
(Tooby & Cosmides, 1992). On this basis, the genes that coded
for that characteristic were more likely to be passed to future
generations than were the genes that did not. This process,
often termed natural selection, favors characteristics that
helped our human ancestors survive or the species propagate.
Our bipedal ancestors, for example, had a significant survival
advantage over those who moved on four limbs (e.g., improved
predator avoidance, greater thermoregulatory efficiency, wider
dietary choice and availability, and freedom of the arms and
hands). Genes that resulted in anatomical, neural, or physio-
logical characteristics that facilitated bipedal locomotion
were in turn more likely to propagate through the species
than those that did not. Natural selection also appears to
have built a degree of economy into evolved characteristics;
they solved adaptive problems without extorting huge costs
from the individual (Williams, 1966). For example, despite
its complexity in coordination and control terms and relative
instability in mechanical terms (Lewin & Foley, 2004), walk-
ing often seems effortless and automatic to the individual. It
also has a relatively low energy cost in comparison with other
forms of movement (Shephard & Åstrand, 2000).
The field of evolutionary psychology addresses the natural
selection of mental characteristics. Generally, the same prin-
ciples as outlined above apply; that is, an adaptive psycho-
logical characteristic is more likely than a nonadaptive one
to propagate through the species (Tooby & Cosmides, 1992).
Evolutionary psychologists consider the adaptive function
of psychological processes and their implications for
behavior. In common with the study of many psychological
phenomena, such analyses are generally done with little ref-
erence to physiology or anatomy. However, in addressing the
evolution of psychological characteristics, it is important to
consider that these did not evolve independently of anatomi-
cal or physiological characteristics. All psychological phe-
nomena are a function of the brain, and the brain relies on
glucose to function. Despite its small size relative to other
organs, the brain accounts for up to 20% of the body’s daily
glucose consumption (Dunbar, 1998); at rest or in a fasted
state it can consume up to 55% of body glucose (Wang &
Mariman, 2008). Areas of the brain that are active at any one
point in time use more energy and nutrients than do inactive
areas at that point in time (Greenfield, 2001). Cerebral blood
flow is redirected to areas requiring nutrients and away from
areas that do not require nutrients (Peppiatt & Attwell, 2004).
Psychological function therefore depends on physiological
processes such as the ingestion and transport of nutrients.
These physiological processes logically evolved either before,
or alongside, the psychological phenomena in question.
Returning to the glucose hypothesis, given the reliance
of the brain on glucose, the proposals that blood glucose is
reduced after a self-control task and that low levels of glucose
might result in a failed attempt at self-control are logical.
There is consequently intuitive appeal to the idea that glucose
is the resource underlying self-control. In the evolutionary
context, however, the idea that a single attempt at self-control
in an everyday situation would deplete brain glucose suffi-
ciently to compromise further attempts suggests that the pro-
cess of self-control is highly uneconomic. This in turn suggests
that the body has no evolved mechanism to either store suf-
ficient glucose or replenish brain glucose quickly. Taken
together, these factors suggest that a restricted capacity to exert
self-control is adaptive. That is, on the basis that acquired
psychological characteristics are a feature of the modern
brain because they solved a problem in our ancestral past,
a limited capacity for self-control may have provided our
ancestors with a survival or procreation advantage. This pres-
ents the question: What adaptive purpose would limited self-
control serve?
Gailliot and Baumeister (2007) presented two evolution-
based explanations for the high cost of self-control. First,
they argued that as an act of self-control often goes against
hard-wired and well-evolved processes, it is necessarily more
effortful and less economic than those same hard-wired pro-
cesses. Second, they proposed that self-control evolved rela-
tively recently and cited Wilder’s (1948) “last in–first out”
rule, suggesting that processes that developed more recently
are the first to become impaired in the absence of sufficient
resources.
The above arguments are seemingly logical. Like most
other human psychological and biological processes, in the
healthy individual, the human brain functions effectively and
economically in most situations. Effectiveness and economy
4 Personality and Social Psychology Review XX(X)
of function are achieved in part via numerous automated, or
hard-wired, mental processes (LeDoux, 1998). Hard-wired
mental processes are a feature of the modern brain because
they helped our forbearers to survive. Their survival in turn
ensured that the genes that coded for the mental process in
question (e.g., fear responses) were handed down to the next
generation. A hard-wired process that helped ensure the sur-
vival of previous generations represents a valuable asset to
the individual who currently possesses it. However, if it is an
automatic process, that individual may be unaware of either
the presence or the value of the process. He or she might
therefore be unaware of the implications of selecting a dif-
ferent course of action to that hard-wired response, and do so
to their cost (fear arguably represents a good example of a
hard-wired and automatic process, whereas curiosity repre-
sents a course of action that might override it). Thus, natural
selection might have resulted in one or more restraint mecha-
nisms that would discourage an individual from overriding
hard-wired processes. As suggested by Gailliot and Baumeister
(2007), an excessively high glucose cost associated with
overriding the hard-wired response would be an effective
restraint mechanism. If such a physiological restraint existed,
using self-control to overcome, for example, a legitimate fear
response would be something an individual would not
choose to do very often.
The suggestion that the limited capacity for self-control
proposed in the strength model may have been adaptive in
the world in which humans evolved is not without support. It
has been argued that given the thousands, if not tens of thou-
sands of generations over which natural selection operated
(Stearns & Hoekstra, 2005), adaptations present in the human
race today evolved in response to problems that confronted
our ancestors in the distant past. These problems may not con-
front us any more (Tooby & Cosmides, 2005). The environ-
ment in which the majority of the world’s population lives
has changed substantially during an extremely short period
in human evolutionary terms, and in far less time than that
required for substantial adaptation to occur. Thus, many
evolved characteristics that were adaptive in the past might
be largely unnecessary or redundant in the modern world.
Furthermore, many characteristics may even be considered
problematic in the relatively safe and ordered contemporary
environment. The fight-or-flight response, for example, although
occasionally adaptive, is likely to contribute to a range of
undesirable phenomena, with “road rage” and panic attacks
being two examples. It is possible that a limited supply of glu-
cose for self-control that in the past ensured that hard-wired
mechanisms such as fear and anger were not often overridden
may be a survival mechanism that is simply no longer required
as frequently today.
Despite the underlying logic of their evolutionary argu-
ments in isolation, there are problems with Gailliot and
Baumeister’s (2007) evolutionary arguments when taken col-
lectively. In citing the last in–first out rule and suggesting that
self-control is a relatively recent acquisition in evolutionary
terms, Gailliot and Baumeister appeared to propose that the
overcoming of hard-wired processes was not something
required from the earliest stages of human evolution. This
seems a weak position; for example, early human beings
would certainly have needed to overcome fear, one of the
strongest hard-wired processes (LeDoux, 1998), to eat, mate,
and secure safe shelter. Natural selection likely would have
favored individuals who were able to respond in accordance
with their fear when it was consistent with priorities and to
exert self-control over that fear when it was inconsistent with
priorities. Fleeing in response to fear of an aggressive animal
makes good sense if you have adequate food, but when you
are close to starvation, the ability to regulate the fear response
and kill the animal to secure a meal is adaptive. Therefore,
it is reasonable to suggest that evolutionary processes would
have ensured the relative economy of self-control (this is not
to say that there would have been no cost; as suggested above,
regulating emotions too easily would not have been adaptive).
In short, it might be presumed that given self-control was often
required for survival, natural selection would have ensured
either the economy of the brain activity underlying self-control
or the sufficient replenishment of brain glucose.
Furthermore, even had the need to exert self-control appeared
relatively recently in human prehistory, this factor would not
fully explain the impairment of energy availability or delivery
posited in the glucose hypothesis. Several other psychological
characteristics are likely relatively recent acquisitions. For
example, the “social emotions” of shame and embarrassment
would have served little adaptive purpose—and would not
have been selected for under evolutionary pressure—unless
individuals who possessed them functioned within large
social groups. As large social groups are a relatively recent
feature of human existence, the social emotions are logi-
cally also a relatively recent acquisition (Lazarus, 1991).
Despite their relative youth, however, these emotions are
associated with specific patterns of physiological response
(Harris, 2001).
In the face of arguments for the concurrent evolution of
mental and physiological processes, it is perhaps Gailliot and
Baumeister’s (2007) suggestion that “evolution might have
repeatedly selected in favor of hominids with a progressively
higher capacity for self-control, even if it did burn a lot of fuel”
(p. 305) that is most problematic. This point seems to suggest
that although natural selection has selected for the capacity
for self-control, the energy cost of self-control would have
remained high throughout evolutionary history. In short,
they suggested that a cognitive mechanism that requires
energy to function evolved in the absence of an adequate
energy supply. In a similar manner to the redirected blood
flow associated with the flight-or-fight response to anger
and fear, the physiological processes associated with self-
control would have been susceptible to the same evolutionary
forces that resulted in the cognitive component of self-control.
In short, if as Gailliot and Baumeister suggested the cogni-
tive component of self-control has been so well served by
evolutionary processes, why has the energy delivery compo-
nent not been?
Beedie and Lane 5
Adaptive Mechanisms
at the Individual Level
We have questioned the proposal that self-control is a recently
acquired cognitive characteristic and the implied suggestion
that the cognitive component of the process would have
evolved without sufficient energy resources. However, an
argument based solely on principles of human evolution is
weak in several respects. We therefore turn to an argument
for which there is substantial empirical support—that even if
evolution did not select at the species level for the ability to
intentionally exert self-control, physiological adaptation at
the individual organism level would ensure improvements in
the economy and effectiveness of self-control. That is, the
demand for brain glucose resulting from repeated attempts at
self-control in everyday life would result in improved glucose
supply to the brain (it should be emphasized that the self-
control tasks used in studies reported by Gailliot & Baumeister,
2007, are similar to many self-control tasks in daily life rather
than life-threatening or highly stressful situations).
The ability of most human beings to adapt to repeated
environmental stressors, such as variations in climate, nutrient
availability, and physical demands, is well documented (Lane,
Terry, Stevens, Barney, & Dinsdale, 2004; Lewin & Foley,
2004; Shephard & Åstrand, 2000; Stearns & Hoekstra, 2005;
Wilmore, Costill, & Kenney, 2008). It is reasonable to sum-
marize what are extremely complex adaptive processes as
follows: When an environmental stressor challenges an indi-
vidual, one or more evolved physiological responses are
activated. Examples of these are thermoregulation in adverse
climatic conditions, increased fat metabolism in the absence
of glucose-rich foods, or increased oxygen supply to working
muscles to sustain movement. Collectively, such responses
ensure the survival of the individual while maintaining a
stable internal physiological environment, or homeostasis
(Wilmore et al., 2008). Repeated demands for the same
response generally lead to one or more physiological adapta-
tions, ensuring that the required response is more economi-
cal or effective in similar future situations. An appropriate
and well-researched model for this process is the endurance
capacity of distance athletes. This capacity is the result of
adaptation to repeated training stress and results in increased
respiratory capacity of the muscle fibers, slower utilization
of muscle glycogen, greater reliance on fat oxidation, and
lower lactate production during movement of a given inten-
sity (Drexler, 1992; Shephard & Åstrand, 2000; Wilmore
et al., 2008). Such functional adaptations are themselves the
result of adaptations in anatomy (e.g., increased number of
capillaries carrying blood and nutrients to a specific body
tissue), biochemistry (e.g., reduced epinephrine secretion for
a given stimulus), or process (e.g., altered motor unit recruit-
ment patterns).
When this adaptive process is applied to the glucose hypoth-
esis it can be suggested that if greater levels of glucose were
required for effective brain function, such repeated demands
for glucose would have resulted in adaptation in the physio-
logical systems involved. This is in fact the case; for exam-
ple, the brains of hypoglycemic individuals adapt to lower
levels of blood glucose by increasing the number of glucose
transporter sites (Nelhig, 1997). Furthermore, data suggest
that such adaptive processes might require relatively little
time; during the brief period of pregnancy, the blood glucose
availability to the mother increases in response to the greater
energy demands of carrying the developing fetus (Weissgerber
& Wolfe, 2006). In short, adaptations in most tissues, organs,
and systems are not only possible but essential for growth,
learning, health, and survival.
In light of the above observations, we argue that in response
to repeated demands for brain glucose, one or more of the
organs or systems involved in self-control would adapt to
ensure more effective and economic self-control in future
situations. Such adaptations might include increased glucose
transporter sites (e.g., Nelhig, 1997) or increased glucose
availability (e.g., Weissberger & Wolfe, 2006). Alternatively,
the nervous system of the individual might adapt and better
coordinate the neural processes underlying self-control. In
the latter scenario, presumably self-control would become
less effortful and so would require less glucose. Of course,
both energy delivery and neural adaptations could take place
concurrently. In fact, in citing the findings of Haier, Siegel,
Tang, Abel, and Buchsbaum (1992), who reported that the
energy cost of playing computer games reduced dramatically
after only 2 months, Gailliot and Baumeister (2007) seem to
acknowledge not only that physiological adaptations to
repeated mental tasks occur but also that they can do so rela-
tively quickly.
Given the above, it seems unlikely that the organs and sys-
tems responsible for the supply of glucose to the brain would
be unable to adapt to ensure efficient self-control. Despite the
apparent strength of the evidence in their review, evidence
for physiological adaptation potentially undermines Gailliot
and Baumeister’s (2007) argument that low glucose and poor
self-control are causally related.
The Physiology of Glucose Transport
We have argued that both natural selection and physiological
adaptation, over both very large and relatively small times-
cales, respectively, would ensure the efficient delivery of
glucose to the brain centers responsible for self-control. We
now turn to the mechanisms by which the body fuels the
brain in this context.
Gailliot and Baumeister (2007) proposed two main argu-
ments in support of the glucose hypothesis. First, “effortful,
controlled, or executive processes are quantitatively differ-
ent from other processes in that they require more glucose”
(p. 306). Second, “glucose can be consumed in the brain faster
than it can be replenished however, and so cerebral activities
can deplete the brain’s supply of glucose” (p. 306). The
validity or otherwise of the first argument is not critical to
6 Personality and Social Psychology Review XX(X)
the glucose hypothesis. That is, the failure of self-control
observed in the studies reported above cannot be explained
by a high glucose cost alone. The high-glucose cost would
not be a problem if the body were able to replace that energy
quickly (e.g., sustained movement has a high energy cost
compared to mental function, but that energy cost is met by
the efficient transport of relatively large quantities of nutri-
ents to the muscles and organs involved). The validity of the
second argument is however critical, as it suggests a dispar-
ity between the energy required by the brain and the body’s
ability to supply that energy.
Kurzban (2010) presented a compelling rebuttal of many
of the claims of the glucose hypothesis. He presented five
key arguments. First, the amounts of glucose used by the brain
per unit time are extremely small in relation to whole body
levels. Second, Gailliot et al. (2007) used a measure of glu-
cose not sufficiently sensitive to identify reliably the reduc-
tions in blood sugar reported.2 Third, the placebo drink used
in that same study contained substantially more calories of
glucose than are depleted by self-control (thus undermining
the claim that a glucose drink will offset ego depletion better
than a placebo). Fourth, whereas the glucose hypothesis dis-
cusses ego depletion in terms of relative reductions in brain
glucose, it does not discuss brain glucose in absolute terms.
(Kurzban, 2010, likened this to considering the drop in the
charge of a battery as opposed to considering the remaining
charge in that battery, the latter being the factor that decides
the available energy.) Last, neuroscience data suggesting no
differences in the energy requirements of different brain
processes undermines the glucose hypothesis further still.
Beyond Kurzban’s (2010) rebuttal and contrary to the
second argument of the glucose hypothesis, evidence also
suggests the body is able to supply energy to the brain quickly
and effectively and has likely evolved to do so during periods
of acute and chronic stress. The brain is the only organ in the
body that does not show weight loss during prolonged starva-
tion or malnutrition, suggesting its primary position in sur-
vival and nutrition (Wang & Mariman, 2008). The selfish brain
theory (Peters et al., 2004) posits that the brain allocates
energy to itself to meet its own energy needs ahead of those
of peripheral tissue and organs. Examples of such “selfish”
allocation of energy include the release of glucose from the
liver into the bloodstream to fuel brain processes in response
to stress (Coker & Kjaer, 2005), increased ketone production
(Minninnen, 2004; Wang & Mariman, 2008), the metabolism
of blood lactate (Oltmanns et al., 2008, Wang & Mariman,
2008), and the rapid increase of its own phosphate content
(Oltmanns et al., 2008). During periods of low blood glucose,
the brain maintains its glucose supply by determining that
peripheral organs derive their energy through other substrates,
for example, fat or protein (Wilmore et al., 2008). Furthermore,
brain glucose will be prioritized over the working muscles
even during intense muscular activity (Wilmore et al., 2008).
The idea of the selfish brain is consistent with evolu-
tionary theory. The chances of an individual surviving an
environmental challenge with a well-fueled brain and depleted
muscles were probably greater than of surviving the same
challenge with well-fueled muscles and a depleted brain. (In
situations except extreme fear, which often required little
deliberation and immediate movement, it was probable that
brain processes such as emotion regulation, recall, problem
solving, and strategic planning were as fundamental to sur-
vival as was movement.) Each of these mental processes
requires glucose. In this context, it is also important to note
that fatty acids do not cross the blood–brain barrier, whereas
skeletal muscles can use large quantities of fats as energy
for movement (Wilmore et al., 2008). Consequently, if body
glucose is low, the supply of free fatty acids to the periphery
is also increased (Wang & Mariman, 2008). Collectively,
this pattern suggests that in drawing glucose away from
the periphery, the brain would not necessarily compromise
movement.
On the basis of the above, the second argument of the
glucose hypothesis as expressed by Gailliot and Baumeister
(2007)—that glucose can be consumed in the brain faster than
it can be replenished and that cerebral activities can therefore
deplete the brain’s supply of glucose—seems questionable.
Interestingly, in the context of the physiology of glucose
transport, Gailliot and Baumeister cited data potentially
undermining the glucose hypothesis. They suggested that
students experienced large increases in glucose before exam-
inations, an activity requiring mental resources. This finding
is consistent with the notion that glucose is released by the
liver into the blood stream to fuel brain processes in response
to stress (Coker & Kjaer, 2005). Furthermore, Gailliot and
Baumeister reported that measures of anxiety predicted levels
of glucose, with the most anxious students having the highest
levels. These authors also suggested that the glucose levels of
individuals increase on days when they are under stress and
that those who dispositionally treat events as stressful tend to
exhibit higher levels of cerebral glucose. Summarizing these
observations, they suggested, “In the face of stress, the body
attempts to cope by converting stored energy into glucose
and releasing it into the bloodstream, thereby increasing
the flow of glucose to the brain, because stressful situations
demand increased cognitive activity” (p. 317). Although this
statement does not necessarily contradict the second argu-
ment of the glucose hypothesis, it does muddy the waters.
That is, the idea that the body is able to produce extra glucose
in response to stress yet is unable to do so in sufficient time or
quantity to maintain self-control is again at odds with evolu-
tionary theory and with the principles of physiological
adaptation. Given the points above, it seems implausible
that the body would be unable to supply sufficient glucose
to the brain.
A Resource Allocation
Model of Self-Control
Gailliot and Baumeister (2007) argued that the failure to
exert self-control is a function of limited glucose supply.
Such a metabolic limitation, however, would appear to be
Beedie and Lane 7
rare in human mental functioning. As suggested, in high stress
or life-threatening situations, when status, power, or even
survival is at stake, energy in the form of glucose is made
available to body tissue by the liver. The seriousness of any
situation to the individual determines the amount of blood
glucose made available to whichever body system is required
to deal with that situation. This process is the result of natu-
ral selection, and several psychological processes, such
as motivation and emotion, have evolved to facilitate it.
Collectively, these responses ensure that in all but the most
critical and life-threatening situations, the body has sufficient
glucose to support brain function.
Perhaps then, the key to the issue of self-control is not the
question of whether the body has sufficient reserves of glu-
cose to fuel mental processes but rather the sites to which
glucose is allocated and why. In fear, the flow of blood, and
therefore of nutrients such as glucose, is directed away from
the central organs such as the digestive system and toward the
limbs. The blood flow of the brain is similarly driven by pri-
ority (Greenfield, 2001; Peppiatt & Attwell, 2004). Glucose-
rich blood is directed to the brain areas required to meet
immediate priorities. Although the rate of requirement will
sometimes exceed the rate of supply, situations in which this
occurs are likely to be rare and could result from either unex-
pected demands or the failure to anticipate factors in the envi-
ronment that will require increased glucose. Although the
brain cannot store glucose, it can mobilize appropriate resources
if primed by information suggesting that glucose will be
needed. Certainly, glucose is a factor in self-control; if there
is no glucose in the blood that has been redirected to the brain,
then logically glucose depletion will be the cause of failed
self-control (although this would occur only in either extreme
starvation or severe illness). However, if the reason for a lack
of glucose in the brain areas responsible for self-control is
that there has been no priority-driven redirection of resources,
low glucose per se is not the cause of a failed attempt at self-
control. That is, insufficient glucose availability is the result
of insufficient blood flow, itself the result of the self-control
task not being sufficiently consistent with personal priorities
to cause physiological reprioritization.
As an alternative to Gailliot and colleagues’ (De Wall,
Baumeister, Gailliot, & Maner, 2008; Gailliot, Peruche, Plant,
& Baumeister, 2009; Gailliot and Baumeister, 2007; Gailliot
et al., 2007) model of self-control based on glucose availabil-
ity, we propose an alternative interpretation. Although our
model does not dispute the role of glucose as the resource of
self-control, it is not a limited resource model but rather a
resource allocation model. Unlike the advocates of the glucose
hypothesis, we argue that the apparent failure of self-control
observed in ego-depletion research is symptomatic of efficient
and economic brain function (directing blood to where it is
needed and away from where it is not needed) as opposed to a
failure of the body to supply sufficient energy. The body has
sufficient glucose to fuel mental processes in all but the
most extreme situations. However, this resource is allo-
cated only when necessary, and that necessity is determined
by responses to the environment in relation to personal
priorities.
Task is consistent
with priorities of
individual (i.e.,
important, urgent)
Task is
inconsistent with
priorities
(not important, not
urgent)
Liver does not
increase
glucose
availability. No
other
physiological
processes
facilitate
energy transfer
High
availability of
blood glucose
Low availability
of blood
glucose
Successful
attempt
Low glucose
risks compro-
mising other
functions
Unsuccessful
attempt
(demand too
high, repeated
attempts result
in low glucose)
Energy levels Appraisal of
task
Energy transfer
Motivation to
self-control
reduced in
order to
maintain
glucose for
more important
functions
Motivation
maintained or
increased.
Individual
persists with
task. Liver
continues to
supply glucose
Motivation Self control
outcome
Withdrawal
from attempt
Liver increases
glucose
availability to
meet
demands.
Physiological
facilitation of
energy transfer
Figure 1. A resource allocation model of self-control
8 Personality and Social Psychology Review XX(X)
Figure 1 illustrates several hypothetical relations between
self-control, glucose levels, appraisal of task, and motivation.
The model is doubtless a simplification, especially in sug-
gesting that these processes occur in linear time and not con-
currently or in multiple feedback loops. Even so, it provides
some testable hypotheses.
The model depicts the self-control process as one by which
the individual becomes aware of the need to exert self-control
and appraises both the requirements of that task and the degree
to which it is consistent with current priorities. If the appraisal
suggests that the self-control task has potential implications
for personal priorities, a motivational response results that
has implications for energy release and transport. In the top
(flat) pathway in Figure 1, the individual has sufficient glu-
cose to exert self-control in almost any situation. The indi-
vidual recognizes these sufficient resources, and the person is
sufficiently motivated to attempt self-control. In the middle
(ascending) pathway, the individual initially has low (insuf-
ficient) glucose in the areas of the brain responsible for self-
control. Appraisal indicates that succeeding with the self-control
task is important. This results in a motivational or emotional
response, perhaps of anxiety, and this response in turn facili-
tates the release of liver glucose into the bloodstream and its
redirection to the brain areas responsible for self-control.
From this point, at which the individual recognizes sufficient
resources, the path follows that of sufficient resources.
In certain rare situations, the focus of the self-control
attempt may be intense, for example, regulating an extreme
emotional response such as rage or performing an especially
demanding cognitive task such as concentrating on a life-
threatening situation. Such scenarios might require repeated
self-control attempts. However, other mental or physical pro-
cesses involved in responding to the situation might also require
substantial energy, thereby competing with self-control for
glucose. These factors might reduce whole body glucose to
a level sufficiently low for the self-control task to become
inconsistent with immediate priorities. The constant redirec-
tion of glucose for self-control might compromise these other
important processes, and blood would be directed away from
the self-control regions. In such a scenario (indicated by the
dotted pathway in Figure 1), the path would revert to the
lowest, descending pathway. In simple terms, the body is con-
serving its resources, a suggestion consistent with the pro-
posal above that conservation might explain ego-depletion
effects.
In the lowest pathway, an appraisal of the situation requir-
ing self-control indicates that it is inconsistent with the pri-
orities of the individual. On that basis, there is no significant
motivational response to the appraisal (the intensity of the
motivational response being proportional to the significance
of the priority to the individual). We propose that the lower
pathway characterizes many examples of failed self-control
in the research findings reported by Gailliot and colleagues
(De Wall, Baumeister, Gailliot, & Maner, 2008; Gailliot,
Peruche, Plant, & Baumeister, 2009; Gailliot and
Baumeister, 2007; Gailliot et al., 2007). If the appraisal of
a task is that it is inconsistent with priorities, the partici-
pant will not benefit from any increase or redirection of
glucose with which to fuel that or any further self-control
attempts. On that basis, he or she would either fail to exert
self-control or disengage from the task.
Two testable hypotheses, and several subhypotheses, arise
from this model. First, irrespective of their initial glucose
levels, participants who are confronted by a self-control task
of personal relevance will persist with the self-control attempt;
they will likely be successful depending on the difficulty of
the task, and their blood glucose levels will be either unchanged
or will increase (although the measurement of blood glucose
should be considered in the context of the caution in the sec-
tion below). The only factor likely to interfere with this pro-
cess is a conflicting priority (easily controlled for or tested in
the laboratory) or a loss of interest in the task. Second, irre-
spective of initial glucose levels, when participants are con-
fronted with a self-control task of low personal relevance,
they will either not persist with the task, in which case their
blood glucose will remain unchanged, or they will persist
and their blood glucose will reduce.
To test this model, the issue of how personally relevant or
meaningful an experimental task is—or is not—to a group of
experimental participants should be considered. Researchers
should determine these relations ahead of conducting experi-
ments, either via empirical means such as pilot work or ratio-
nally by selecting participants hypothetically matched to
tasks. In this context, it is not unreasonable to propose that
tasks used in previous ego-depletion research might be con-
sidered more meaningful to some participants or populations
than to others. For example, resisting eating chocolate (e.g.,
Baumeister et al., 1998, Study 1) might be more meaningful
to overweight dieters than to normal weight language stu-
dents, whereas a language correction task (e.g., Baumeister
et al., 1998, Study 4) might be meaningless to the dieters yet
highly meaningful to the language students. Emotion suppres-
sion or expression (e.g., Muraven et al., 1998, Study 1)
or speech control tasks (e.g., Muraven & Slessareva, 2003,
Study 2) are hypothetically meaningful to drama students but
not to college athletes. A physical endurance task (e.g., Moller,
Deci, & Ryan, 2006, Study 1), however, might be meaningful
to the college athletes but not to the drama students.
Simply presenting the experimental task to participants
without context would probably not maximize the meaning-
fulness of the task. For example, if the emotion expression
task were presented to drama students without an explicit link
to the requirements of their area of study, it may not be as
meaningful to them as if it were communicated with such an
explicit link. In similar vein, it is likely that the meaningful-
ness of a task can be augmented by, for example, filming it,
requiring that it is performed before peers or by informing
participants that the results of the tasks will be made public.
Beedie and Lane 9
In the above examples of experimental tasks, each is hypo-
thetically as meaningful to one group as it is relatively mean-
ingless to the other. This contrast provides some potential for
interesting experimentation, and using two such tasks and
two such distinct groups of participants in one dual-task study
would represent a good test of the RAMS. For example,
drama students and college athletes could each be split into
two groups, forming four groups. One group of the drama stu-
dents and one group of the college athletes would attempt the
task that is hypothetically meaningful to them, that is, emotion
regulation and physical endurance, respectively. The other
two groups would attempt their respective relatively mean-
ingless task (i.e., the athletes would attempt the emotion regu-
lation and the drama students the physical endurance). In this
design, the RAMS predicts that lower ego depletion and
higher blood glucose would be observed among the two
groups performing their respective meaningful tasks.
As we have suggested, whatever the task or population
chosen for a study, identifying the priorities of participants, or
recruiting participants to whom the task is meaningful, should
form part of the research process. Even so, the degree to
which any selected task is meaningful to any one individual
will vary substantially, even within apparently homogeneous
groups. On this basis, beyond the strategic selection of hypo-
thetically matched tasks and participants described above,
post hoc quantitative and qualitative assessment of the degree
to which participants perceived the task as meaningful should
be conducted. The mechanisms of self-control are more
likely to be elucidated if researchers have data indicating the
perceived meaningfulness of a task and if they are able to
ascertain from participants, in those participants’ own words,
why they believe they did or did not achieve self-control.
Finally, but importantly, in testing the glucose hypothesis,
the most sensitive and reliable measure of glucose should be
used (see Note 2). As the degree to which brain glucose and
body glucose correlate is a matter still open to debate, this
factor must be considered in future designs, for example, via
measurement of the glucose content of blood flowing into
and out of the brain (e.g., Masden et al., 1995). Inferring
brain glucose levels through changes in peripheral glucose
might present a false picture of the true glucose costs of
self-control.
Summary
Research has suggested that self-control relies on a lim-
ited resource. On the basis of what is understood about the
energy requirements of the brain, it is reasonable to argue
that glucose could be that resource. However, counter to
the glucose hypothesis proposed by Gailliot and col-
leagues (De Wall, Baumeister, Gailliot, & Maner, 2008;
Gailliot, Peruche, Plant, & Baumeister, 2009; Gailliot
and Baumeister, 2007; Gailliot et al., 2007) (and argu-
ably to the strength model more generally), we argue
that the resource issue is one of allocation, not of limited
supply. Although the evidence for the glucose hypothesis
of self-control seems compelling at first view, we have
identified some inconsistencies in the theory underpin-
ning the model. Our alternative account is rooted in the
evolution of mental processes at the species level, the
adaptation of these processes at the individual level, and
the physiology of glucose transport. The basis of our
approach is that given the apparent complexity and thor-
oughness of evolutionary processes, any apparent failure
in relatively simple human function is more likely an
evolutionary design feature than a design flaw. This holds
true even if the design feature in question presents prob-
lems in a social environment more complex than that in
which it evolved to function.
In proposing our model we have retained a role for glu-
cose, albeit as a physiological mediator of the motivational
and behavioral processes involved in self-control. It is of course
possible that, as suggested by Kurzban (2010), the levels of
glucose involved in self-control are so small as to be irrele-
vant in research or application. However, we believe that to
dismiss the role of glucose without further empirical work
would be premature. We have no doubt that, just as we have
critiqued Gailliot and Baumeister’s (2007) proposals, our
proposals will be questioned, and we welcome this response;
our aim in writing the present article was not to dismiss the
glucose hypothesis but rather to interrogate it and to stimu-
late more research into what is an interesting interdisciplin-
ary research question.
As the primary form of energy for the brain, glucose is
a factor not only in self-control but in all mental processes.
Baumeister and his colleagues have often used a muscle
metaphor to explain self-control (e.g., Muraven &
Baumeister, 2000). It is certainly instructive to consider the
function of the brain as, in many respects, similar to that of
other body tissue, albeit tissue that regulates its own energy
supply. Regardless of whether future findings corroborate
the glucose hypothesis or the RAMS, we are confident that
the investigation of the role of physiology in mental pro-
cesses will have applications to several disciplines of
psychology.
The RAMS focuses on the meaningfulness of the experi-
mental task and its role in determining the resources available
to the individual to successfully exert self-control in that
meaningful context. We hope that given the early claims for
the importance of self-control strength in areas such as dis-
ease, debt, and violent crime (e.g., Muraven & Baumeister,
2000), research into the glucose hypothesis and the strength
model generally will progress toward these more meaningful
societal issues.
Authors’ Note
The authors thank Professor Peter Totterdell and Dr Richard
Godfrey for their help in preparing this manuscript.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect t o
the research, authorship, and/or publication of this article.
10 Personality and Social Psychology Review XX(X)
Funding
The author(s) disclosed receipt of the following financial support
for the research, authorship, and/or publication of this article: The
support of the Economic and Social Research Council (ESRC)
UK is gratefully acknowledged (RES-060-25-0044: “Emotion
Regulation of Others and Self [EROS]”).
Notes
1. Gailliot (2008) further extended the glucose hypothesis to gly-
cogen although he presented no new data.
2. Both Kurzban (2010) and Gibson (2007) argued that the brain
uses relatively small amounts of glucose. Therefore, the tool to
assess changes in glucose needs to be reliable. Research examin-
ing changes in blood glucose in the self-control literature has
used the Accu-Chek monitor (Roche Diagnostics, Basel,
Switzerland). The Accu-Chek unit is relatively easy to use and
requires little formal training. For example, diabetics use the
device to self-monitor glucose levels. Evidence, however, sug-
gests that the Accu-Chek consistently fails to meet high stan-
dards of test–retest stability (Hoedemaekers, Klein Gunnewiek,
Prinsen, Willems, & Van der Hoeven, 2008; Khan, Vasquez,
Gray, Wians, & Kroll, 2006). Furthermore, Vlasselaers et al.
(2008) found that the bias for the Accu-Chek was 6 mg/dl with
wide limits of agreement and a variable over- and underestima-
tion of the actual blood glucose value depending on the level of
BG (hypo-, normo-, or hyperglycemia). On this basis, it seems
that critical comments relating to the validity of the glucose
measures reported in the self-control literature are not without
foundation.
References
American Psychological Association. (2010, May). New APA Com-
mittee on Human Research sets its agenda. Retrieved from http://
www.apa.org/science/about/psa/2010/05/human-research.aspx
Baumeister, R. F. (2003). Ego depletion and self-regulation
failure: a resource model of self-control. Alcoholism: Clini-
cal and Experimental Research, 27(2), 1-4. doi:10.1097/01.
ALC.0000060879.61384.A4
Baumeister, R. F., Bratslavsky, E., Muraven, M., & Tice, D. M.
(1998). Ego depletion: Is the active self a limited resource?
Journal of Personality and Social Psychology, 74, 1252-1265.
doi:10.1037/0022-3514.74.5.1252
Baumeister, R. F., Heatherton, T. F., & Tice, D. M. (1994). Losing
control: How and why people fail at self-regulation. San Diego,
CA: Academic Press.
Cohen, J. (1987). Statistical power analysis for the behavioral
sciences (2nd ed.). Hillsdale, NJ: Erlbaum.
Coker, R. H., & Kjaer, M. (2005). Glucoregulation during exercise:
The role of the neuroendocrine system. Sports Medicine, 35,
575-583. doi:10.2165/00007256-200535070-00003
DeWall, C. N., Baumeister, R. F., Gailliot, M. T., & Maner, J. K.
(2008). Depletion makes the heart grow less helpful: Helping
as a function of self-regulatory energy and genetic relatedness.
Personality and Social Psychology Bulletin, 34, 1653-1662. doi:
10.1177/0146167208323981
Drexler, H. (1992). Skeletal muscle failure in heart failure. Circulation,
85, 1621-1623.
Dunbar, R. I. M. (1998). The social brain hypothesis. Evolutionary
Anthropology, 6, 178-190. doi:10.1002/(SICI)1520-6505(1998)
6:5<178::AID-EVAN5>3.0.CO;2-8
Gailliot, M. T. (2008). Unlocking the energy dynamics of executive
functioning: Linking executive functioning to brain glycogen.
Perspectives on Psychological Science, 3, 245-263. doi:10.1111/
j.1745-6924.2008.00077.x
Gailliot, M. T., & Baumeister, R. F. (2007). The physiology of will-
power: Linking blood glucose to self-control. Personality and
Social Psychology Review, 11, 303-327. doi:10.1177/108886
8307303030
Gailliot, M. T., Baumeister, R. F., DeWall, C. N., Maner, J. K.,
Plant, E. A., Tice, D. M., . . . Schmeichel B. J. (2007). Self-
control relies on glucose as a limited energy source: Willpower
is more than a metaphor. Journal of Personality and Social
Psychology, 92, 325-336. doi:10.1037/0022-3514.92.2.325
Gailliot, M. T., Peruche, B. M., Plant., E. A., & Baumeister, R. F.
(2009). Stereotypes and prejudice in the blood: Sucrose drinks
reduce prejudice and stereotyping. Journal of Experimental
Social Psychology, 45, 288-290. doi:10.1016/j.jesp.2008.09.003
Gibson, E. L. (2007). Carbohydrates and mental function: Feeding
or impeding the brain? British Nutrition Foundation Nutrition
Bulletin, 32(Suppl. 1), 71-83.
Gordijn, E. H., Hindriks, I., Koomen, W., Dijksterhuis, A., & van
Knippenberg, A. (2004). Consequences of stereotype suppres-
sion and internal suppression motivation: A self-regulation
approach. Personality and Social Psychology Bulletin, 30, 212-
224. doi: 10.1177/0146167203259935
Greenfield, S. (2001). The human brain. London, UK: Phoenix.
Hagger, M. S., Wood, C., Stiff, C., & Chatzisarantis, N. L. (2010). Ego
depletion and the strength model of self-control: A meta-analysis.
Psychological Bulletin, 136, 495-525. doi:10.1037/a0019486
Haier, R. J., Siegel, B., Tang, C., Abel, L., & Buchsbaum, M. S.
(1992). Intelligence and changes in regional cerebral metabolic
rate following learning. Intelligence, 16, 415-426. doi:10.1016/
0160-2896(92)90018-M
Harris, C. R. (2001). Cardiovascular responses of embarrassment and
effects of emotional suppression in a social setting. Journal of
Personality and Social Psychology, 81, 886-897. doi:10.1037/
0022-3514.81.5.886
Hoedemaekers, C. W. E., Klein Gunnewiek, J. M. T., Prinsen, M. A.,
Willems, J. L., & Van der Hoeven, J. G. (2008). Accuracy of
bedside glucose measurement from three glucometers in criti-
cally ill patients. Critical Care Medicine, 36, 3062-3066.
Khan, A. I., Vasquez, Y., Gray, J., Wians, F. H., Jr., & Kroll, M. H.
(2006). The variability of results between point-of-care testing
glucose meters and the central laboratory analyzer. Archives of
Pathology & Laboratory Medicine, 130, 1527-1532.
Kurzban, R. (2010). Does the brain consume additional glucose
during self-control tasks? Evolutionary Psychology, 8,244-259.
Beedie and Lane 11
Lane, A. M., Terry, P. C., Stevens, M. J., Barney, S., & Dinsdale, S. L.
(2004). Mood responses to athletic performance in extreme
environments. Journal of Sports Sciences, 22, 886-897
Lazarus, R. S. (1991). Emotion and adaptation, New York, NY:
Oxford University Press.
LeDoux, J. (1998). The emotional brain. London, UK: Orion.
Lewin, R., & Foley, R. (2004). Principles of human evolution. Oxford,
UK: Blackwell.
Madsen P. L., Hasselbalch, S. G., Hagemann, L. P., Olsen, K. S.,
Bulow, J., Holm, S., . . . Lassen, N. A. (1995). Persistent reset-
ting of the cerebral oxygen/glucose uptake ratio by brain acti-
vation: Evidence obtained with the Kety-Schmidt technique.
Journal of Cerebral Blood Flow and Metabolism, 15, 485-491.
Masicampo, E. J., & Baumeister, R. F. (2008). Toward a physiology
of dual-process reasoning and judgment: Lemonade, willpower,
and effortful rule-based analysis. Psychological Science, 19,
255-260. doi:10.1111/j.1467-9280.2008.02077.x
Minninnen, A. H. (2004). Metabolic effects of the very-low-
carbohydrate diets: misunderstood “villains” of human metab-
olism. Journal of the International Society of Sports Nutrition,
1, 7-11. doi:10.1186/1550-2783-1-2-7
Moller, A., Deci, E., & Ryan, R. (2006). Choice and ego-depletion:
The moderating role of autonomy. Personality and Social Psy-
chology Bulletin, 32, 1024-1036
Muraven, M. R., & Baumeister, R. F. (2000). Self-regulation and
depletion of limited resources: Does self-control resemble a mus-
cle? Psychological Bulletin, 126, 247-259. doi:10.1037/0033-
2909.126.2.247
Muraven, M. R., Shmueli, D., & Burkley, E. (2006). Conserving
self-control strength. Journal of Personality and Social Psy-
chology, 91, 524-537. doi:10.1037/0022-3514.91.3.524
Muraven, M. R., & Slessareva, E. (2003). Mechanism of self-
control failure: Motivation and limited resources. Personal-
ity and Social Psychology Bulletin, 29, 894-906. doi:10.1177/
0146167203029007008
Muraven, M. R., Tice, D. M., & Baumeister, R. F. (1998). Self-con-
trol as limited resource: Regulatory depletion patterns. Journal
of Personality and Social Psychology, 74, 774-789. doi:10.1037/
0022-3514.74.3.774
Nelhig, A. (1997). Cerebral energy metabolism, glucose transport
and blood flow: changes with maturation and adaptation to
hypoglycaemia. Diabetes and Metabolism, 23, 18-29.
Oltmanns, K. M., Melchert, U. H., Scholand-Engler, U. G., Howitz, M. C.,
Schultes, B., Schweiger, U., . . . Pellerin. L. (2008). Differential
energetic response of brain vs. skeletal muscle upon glycemic
variations in healthy humans. American Journal of Physiology:
Regulatory, Integrative, Comparative Physiology, 294, R12-R16.
doi:10.1152/ajpregu.00093.2007
Peppiatt, C., & Attwell, D. (2004). Food for thought. Nature, 431,
137-138.
Peters, A., Schweiger, U., Pellerin, L., Hubolt, C., Oltmanns, K.,
Conrad, M., . . . Fehm, H. (2004). The selfish brain: Compe-
tition for energy resources. Neuroscience & Biobehavioral
Reviews, 28, 143-180. doi:10.1016/j.neubiorev.2004.03.002
Shephard, R. J., & Åstrand, P. O. (2000). Endurance in sport (2nd
ed., IOC Medical Commission, International Federation of Sports
Medicine). Oxford, UK: Blackwell.
Stearns, S. C., & Hoekstra, R. J. (2005). Evolution (2nd ed.).
New York, NY: Oxford University Press.
Tooby, J., & Cosmides, L. (1992). The psychological foundations
of culture. In J. Barkow, L. Cosmides, & J. Tooby (Eds.), The
adapted mind: Evolutionary psychology and the generation of
culture. New York, NY: Oxford University Press.
Tooby, J., & Cosmides, L. (2005). Conceptual foundations of evolu-
tionary psychology. In D. M. Buss (Ed.), The handbook of evolu-
tionary psychology (pp. 5-67). New York, NY: Wiley.
Vlasselaers, D., Van Herpe, T., Milants, I., Eerdekens, M., Wouters,
P. J., De Moor, B., & Van den Berghe, G. (2008). Blood glucose
measurements in arterial blood of intensive care unit patients
submitted to tight glycemic control: Agreement between
bedside tests. Journal of Diabetes Science and Technology, 2,
932-938.
Vohs, K. D., Baumeister, R.F., & Ciarocco, N. J. (2005). Self-
regulation and self-presentation: regulatory resource depletion
impairs impression management and effortful self-presentation
depletes regulatory resources. Journal of Personality and Social
Psychology, 88, 632-657. doi:10.1037/0022-3514.88.4.632
Wang, P., & Mariman, E. C. (2008). Insulin resistance in an energy-
centered perspective. Physiology and Behavior, 94, 198-205.
doi:10.1016/j.physbeh.2007.11.008
Weissgerber T. L., & Wolfe, L. A. (2006). Physiological adaptation
in early human pregnancy: Adaptation to balance maternal-fetal
demands. Applied Physiology, Nutrition and Metabolism, 31, 1-11.
Wilder, J. (1948), Sugar metabolism and its relation to criminology.
In S. Linder & B. J. Selinger (Eds.), Handbook of correctional
psychology. New York, NY: Philosophical Library.
Williams, G. C. (1966). Adaptation and natural selection. Princeton,
NJ: Princeton University Press.
Wilmore, J. H., Costill, D. L., & Kenney, W. L. (2008). Physiology
of sport and exercise. Champaign, IL: Human Kinetics.
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The long-term scientific goal toward which evolutionary psychologists are working is the mapping of the universal human nature. Evolutionary psychology provokes so much reflexive opposition because the stakes for many social scientists, behavioral scientists, and humanists are so high. If evolutionary psychology turns out to be well-founded, then the existing superstructure of the social and behavioral sciences, the Standard Social Science Model, have to be dismantled. To be effective researchers, psychologists needs to become at least minimally acquainted with the principles of organic design. One reason why cognitive psychologists arbitrarily limit their scope is the folk psychological distinction made between knowledge acquisition on the one hand and motivation, emotion, and preferences on the other. Evolutionary theory when joined with a computational approach to the mind leads to the conclusion that the human psychological architecture is very likely to include a large array of adaptive specializations.
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Conventional wisdom over the past 160 years in the cognitive and neurosciences has assumed that brains evolved to process factual information about the world. Most attention has therefore been focused on such features as pattern recognition, color vision, and speech perception. By extension, it was assumed that brains evolved to deal with essentially ecological problem-solving tasks. 1.
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Past work suggests that executive functioning relies on glucose as a depletable energy, such that executive functioning uses a relatively large amount of glucose and is impaired when glucose is low. Glucose from the bloodstream is one energy source for the brain, and glucose stored in the brain as glycogen is another. A review of the literature on glycogen suggests that executive functioning uses it in much the same way as glucose, such that executive functioning uses glycogen and is impaired when glycogen is low. Findings on stress, physical persistence, glucose tolerance, diabetes, sleep, heat, and other topics provide general support for this view. © 2008 Association for Psychological Science.