The Strength Model of
Roy F. Baumeister,
Kathleen D. Vohs,
and Dianne M. Tice
Florida State University and
University of Minnesota
ABSTRACT—Self-control is a central function of the self
and an important key to success in life. The exertion of
self-control appears to depend on a limited resource. Just
as a muscle gets tired from exertion, acts of self-control
cause short-term impairments (ego depletion) in subsequent
self-control, even on unrelated tasks. Research has
supported the strength model in the domains of eating,
drinking, spending, sexuality, intelligent thought, making
choices, and interpersonal behavior. Motivational or
framing factors can temporarily block the deleterious effects
of being in a state of ego depletion. Blood glucose is an
important component of the energy.
KEYWORDS—self-control; ego depletion; willpower; impulse;
Every day, people resist impulses to go back to sleep, to eat
fattening or forbidden foods, to say or do hurtful things to their
relationship partners, to play instead of work, to engage in in-
appropriate sexual or violent acts, and to do countless other sorts
of problematic behaviors—that is, ones that might feel good
immediately or be easy but that carry long-term costs or violate
the rules and guidelines of proper behavior. What enables the
human animal to follow rules and norms prescribed by society
and to resist doing what it selﬁshly wants?
Self-control refers to the capacity for altering one’s own re-
sponses, especially to bring them into line with standards such
as ideals, values, morals, and social expectations, and to support
the pursuit of long-term goals. Many writers use the terms self-
control and self-regulation interchangeably, but those who make
a distinction typically consider self-control to be the deliberate,
conscious, effortful subset of self-regulation. In contrast,
homeostatic processes such as maintaining a constant body
temperature may be called self-regulation but not self-control.
Self-control enables a person to restrain or override one re-
sponse, thereby making a different response possible.
Self-control has attracted increasing attention from psychol-
ogists for two main reasons. At the theoretical level, self-control
holds important keys to understanding the nature and functions
of the self. Meanwhile, the practical applications of self-control
have attracted study in many contexts. Inadequate self-control
has been linked to behavioral and impulse-control problems,
including overeating, alcohol and drug abuse, crime and
violence, overspending, sexually impulsive behavior, unwanted
pregnancy, and smoking (e.g., Baumeister, Heatherton, & Tice,
1994; Gottfredson & Hirschi, 1990; Tangney, Baumeister,
& Boone, 2004; Vohs & Faber, 2007). It may also be linked
to emotional problems, school underachievement, lack of
persistence, various failures at task performance, relationship
problems and dissolution, and more.
Folk discussions of self-control have long invoked the idea of
willpower, which implies a kind of strength or energy. During the
heyday of the behaviorist and cognitive revolutions, however,
psychology had little use for theorizing in energy terms, and
self theories in particular had scarcely mentioned energy
since Freud. However, in the 1990s, research ﬁndings began to
point toward an energy model of self-control. There might be
something to the willpower notion after all.
The idea that self-control depended on a limited energy
resource was suggested by us (Baumeister et al., 1994) based on
our review of multiple research literatures. We observed that
self-control appeared vulnerable to deterioration over time from
repeated exertions, resembling a muscle that gets tired. The
implication was that effortful self-regulation depends on a limited
resource that becomes depleted by any acts of self-control,
causing subsequent performance even on other self-control
tasks to become worse.
The basic approach to testing the depleted-resource hypothesis
was to have some research participants perform a ﬁrst self-control
task, while others performed a comparable but neutral task, and
Address correspondence to Roy F. Baumeister, Florida State Uni-
versity, Department of Psychology, 1107 W. Call Street, Tallahassee,
FL 32306-4301; e-mail: firstname.lastname@example.org.
CUR R E N T D I R E C T I O N S I N P SYCHO L O G I C A L S C I E N C E
Volume 16—Number 6 351Copyright r2007 Association for Psychological Science
then all would move on to perform a second, unrelated self-
control task. If self-control consumes a limited resource, then
performing the ﬁrst task should deplete the person’s resource,
leaving less available for the second task—and therefore
causing poorer performance on the second task. Other theories
would make different predictions. For example, if self-control
mainly involved activating a cognitive schema or mental
program, then the ﬁrst self-control task should prime the schema
and activate the self-control system, so performance on the
second self-control task should improve, not worsen.
Early laboratory evidence for depleted resources in self-
regulation was reported by Muraven, Tice, and Baumeister
(1998) and Baumeister, Bratslavsky, Muraven, and Tice (1998).
In one study, watching an emotionally evocative ﬁlm while trying
either to amplify or to stiﬂe one’s emotional response caused
poorer performance on a subsequent test of physical (handgrip)
stamina, as compared to watching the ﬁlm without trying to
control one’s emotions. (Stamina counts as a measure of
self-control because it involves resisting fatigue and overriding
the urge to quit.) In another study, suppressing a forbidden
thought weakened people’s ability to stiﬂe laughter afterward.
In another, resisting the temptation to eat chocolates and
cookies (and making oneself eat health-promoting but un-
appetizing radishes instead) caused participants to give up faster
on a subsequent frustrating task, as compared to people who
had not exerted self-control (see Fig. 1). These studies all
pointed toward the conclusion that the ﬁrst self-control task
consumed and depleted some kind of psychological resource
that was therefore less available to help performance on the
second self-control task.
The term ego depletion was coined to refer to the state of
diminished resources following exertion of self-control (or other
tasks that might deplete the same resource). These ego-depletion
effects are not due to a diminished a sense of self-efﬁcacy or to the
inference that one is poor at self-control. Wallace and Baumeister
(2002) explicitly manipulated feedback about success and failure
at self-control and measured self-efﬁcacy, but neither factor had
any discernible impact on the ego-depletion patterns. Nor
are these patterns due to participants refusing to exert themselves
on the second task because they think they have done enough on
the ﬁrst task, as various ﬁndings have shown (see Baumeister,
Gailliot, DeWall, & Oaten, 2006); for example, it has been found
that depleted participants will subject themselves to more
boredom than will nondepleted ones on a second task.
Is willpower more than a metaphor? Gailliot et al. (2007)
explored the role of glucose, a chemical in the bloodstream that
can be converted to neurotransmitters and thus furnishes fuel
for brain activity. Acts of self-control cause reductions in blood-
glucose levels, which in turn predict poor self-control on
behavioral tasks. Drinking a glass of lemonade with sugar helped
counteract these effects, presumably by restoring glucose in
the blood. Lemonade mixed with diet sweeteners (no glucose)
had no such empowering effect.
ELABORATING THE STRENGTH MODEL
The analogy between self-control and a muscle was suggested
by the early ﬁndings that self-control performance deteriorates
after initial exertions, just as a muscle gets tired from exertion.
Other revealing aspects of self-control performance also extend
the resemblance to a muscle (see Box 1).
First, just as exercise can make muscles stronger, there are
signs that regular exertions of self-control can improve willpower
strength (for a review, see Baumeister et al., 2006). These
improvements typically take the form of resistance to depletion,
in the sense that performance at self-control tasks deteriorates at
a slower rate. Targeted efforts to control behavior in one area,
such as spending money or exercise, lead to improvements
in unrelated areas, such as studying or household chores.
And daily exercises in self-control, such as improving posture,
altering verbal behavior, and using one’s nondominant hand
for simple tasks, gradually produce improvements in
self-control as measured by laboratory tasks. The ﬁnding
that these improvements carry over into tasks vastly different
from the daily exercises shows that the improvements are
not due to simply increasing skill or acquiring self-efﬁcacy
Second, just as athletes begin to conserve their remaining
strength when their muscles begin to tire, so do self-controllers
when some of their self-regulatory resources have been
expended. The severity of behavioral impairment during
depletion depends in part on whether the person expects further
challenges and demands. When people expect to have to exert
self-control later, they will curtail current performance more
severely than if no such demands are anticipated (Muraven,
Shmueli, & Burkley, 2006).
Third, and consistent with the conservation hypothesis,
people can exert self-control despite ego depletion if the stakes
are high enough. Offering cash incentives or other motives for
good performance counteracts the effects of ego depletion
(Muraven & Slessareva, 2003). This may seem surprising but in
Eat radish Eat chocolate No-food control
Duration of persistence (min)
Fig. 1. Speed of giving up on an unsolvable task after eating chocolate or
exerting self-control to resist chocolate in favor of radishes on a previous
task (as compared to a no-food control). From Baumeister, Bratslavsky,
Muraven, & Tice, 1998.
352 Volume 16—Number 6
The Strength Model of Self-Control
fact it may be highly adaptive. Given the value and importance
of the capacity for self-control, it would be dangerous for a
person to lose that capacity completely, and so ego depletion
effects may occur because people start conserving their
remaining strength. When people do exert themselves on the
second task, they deplete the resource even more, as reﬂected in
severe impairments on a third task that they have not anticipated
(Muraven et al., 2006).
To be sure, we think there are levels of depletion beyond
which people may be unable to control themselves effectively,
regardless of what is at stake. Pragmatic and ethical limitations
have prevented us from showing this in laboratory work thus far.
Again, the muscle analogy is relevant: Mildly tired athletes can
indeed manage to summon the strength for a major exertion at
decisive moments, but after a certain point fatigue becomes
How far the muscle analogy can be pushed remains an open
question. Are there self-control states resembling sprained or
injured muscles? One might speculate that burnout or
other pathological states resemble the incapacities stemming
from muscles that have been abused beyond their normal
capacity for recovery.
Multiple lines of work have identiﬁed procedures that can
moderate or counteract the effects of ego depletion. Inducing
a state of positive emotion such as humor seems to have that
effect (Tice, Baumeister, Shmueli, & Muraven, 2007). Having
implementation intentions—formulating ‘‘if–then’’ statements
about how to behave in a situation prior to entering it—seems
to be effective most likely because such intentions operate
as behavioral plans and guidelines that reduce the need for
executive control (Webb & Sheeran, 2003). To be sure, none of
these procedures clearly counteracts the depleted state in the
sense of replenishing the depleted resource. Rather, they may all
operate by inducing the person to expend more of the depleted
resource. In contrast, there is some reason to think that
replenishing glucose in the bloodstream does actually rectify the
depletion by restoring the depleted resource (Gailliot et al., 2007).
Understanding self-control has potential applications across
a broad spectrum of human behavior. At the positive end, self-
control is associated with good adjustment, secure attachment,
and other favorable psychological states (Tangney et al., 2004).
At the negative end, poor self-control is associated with elevated
rates of psychopathological complaints and symptoms, as well as
increased vulnerability to various substance-abuse and eating
disorders (Tangney et al., 2004). Evidence that ego depletion
contributes to a variety of problem behaviors—including
excessive alcohol consumption, overeating, sexual misbehavior,
prejudicial discrimination, and violence—is accumulating.
Intelligent behavior is vital to human success, and it depends
partly on self-control. Some processes, such as rote memory, are
fairly automatic and independent of executive control, and these
appear to be relatively unaffected by depletion. But logical
reasoning, extrapolation, and other controlled processes
depend on control by the self, and performance on these tasks
dips sharply when people are depleted (Schmeichel, Vohs, &
Interpersonal processes also seem to hinge on self-regulatory
operations, with some needing self-control more than others.
Richeson and Shelton (2003) reasoned that self-control is needed
for discussing delicate, sensitive issues—for instance talking
about racial politics with a member of a different race—because
one has to avoid saying anything that might give offense or be
misinterpreted. The researchers had White participants engage
in such a conversation with a Black person; afterwards, the
participants showed impaired performance on the Stroop task,
a classic measure of self-control in which participants are
Contexts, Moderators, Mediators, and Implications of the
Responses that require self-regulation include
!Overcoming unwanted impulses (e.g., not eating tempting candies
because of being on a diet)
!Making many choices
Behaviors thatare sensitive to depletion ofself-regulatoryresources include
!Eating among dieters
!Aggression after being provoked
!Intelligent and logical decision making
Interpersonal processes that require self-regulatory resources include
!Self-presentation or impression management
!Kindness in response to a partner’s bad behavior
!Dealing with demanding, difﬁcult partners
Moderators of ego depletion include
!Heightened motivation to achieve a goal
!Collectivistic cultural background
Physical indicators of ego depletion include
!Neural changes using electroencephalograph methods
Mediators of ego depletion include
!Subjective time perception (time perception is elongated—i.e., time
Harmful effects of depletion may be counteracted through
!Humor and laughter
!Other positive emotions
!Implementation intentions (‘‘if ... then’’ plans)
!Social goals (e.g., wanting to help people; wanting to be a good
Volume 16—Number 6 353
Roy F. Baumeister, Kathleen D. Vohs, and Dianne M. Tice
instructed to say the color in which other color words are printed
(e.g., when seeing the word green printed in blue, the participant
must override the automatic response of saying ‘‘green’’ in
order to say ‘‘blue’’). Having such a conversation with a member
of one’s own race does not deplete the self and impair sub-
Presenting a desired image to others can also tax self-control
strength resources (Vohs, Baumeister, & Ciarocco, 2005). After
exerting effort at managing the impression they made (e.g., when
trying to convey a particular image while making a recording),
people showed deﬁcits at self-control. Moreover, and conversely,
after people had exerted self-control, they were less effective at
managing their behavior so as to make a good impression and in
fact sometimes behaved in annoying or off-putting ways.
IMPLICATIONS FOR THEORY
The existence of a single energy resource that is used for a broad
range of self-control acts suggests that self theory must move
beyond merely cognitive models. The self is more than a network
of cognitive schemas: It is a dynamic system able to manage
behavior in advanced, complex, and biologically expensive
The use of the body’s energy for complex action control
extends beyond self-control. Recent studies indicate that the
same energy is used for effortful decision making, as well as for
active rather than passive responses (e.g., Vohs et al., 2007).
These seem to correspond to what laypersons understand as
‘‘free will,’’ namely the ability to override impulses, behave
morally, show initiative, and behave according to rational
choices (Baumeister, in press).
Most broadly, the strength model of self-control offers
suggestions about how and why the human self evolved in its
current form. The functional purposes of the self almost certainly
include managing behavior toward fostering enlightened
self-interest and facilitating group membership by garnering
social acceptance. Self-control is helpful for both these goals.
The role of energy suggests that self-control is a complex,
biologically expensive form of behavior. Thus, we may infer that,
to enable humans to create and sustain the complicated groups
to which they belong, including cultural systems, evolution had
to ﬁnd a way to use the body’s energy to control behavior in
these advanced and subtle ways. For example, human beings
everywhere regulate their behavior according to various rules,
such as social norms, moral principles, and laws.
A particularly broad and important question is what other forms
of behavior (beyond self-control and choice) use this limited
resource: How special is this form of mental effort? We noted that
success at building self-control through exercises has been
inconsistent, so it is also necessary to explore why some
regimens work better than others. Finding a reliable way to
improve self-control would not only shed light on how the self
functions but would also have practical value for therapists,
coaches, educators, parents, and many others.
Identifying the biological substrates of self-control depletion
(and replenishment) would be another helpful direction for
further work. Better understanding of the developmental process
would likewise strengthen the theory and make it more
applicable to human welfare and problems.
Psychology can contribute to society by ﬁnding ways to enable
people to live healthier, more successful, and more satisfying
lives. Self-control is a promising avenue to achieve this. It
appears to facilitate success in life in many spheres, and,
crucially, it appears amenable to improvement. Indeed,
self-control can be grouped with intelligence among the (rather
few) traits that are known to contribute to success in human
life across a broad variety of spheres; yet unlike intelligence,
self-control appears amenable to improvement from psycho-
logical interventions, even in adulthood. The strength model can
illuminate how self-control operates and functions. By building
on this knowledge, psychology may be able to improve the
mental health and well-being of many people.
Baumeister, R.F., Schmeichel, B.J., & Vohs, K.D. (2007). Self-regulation
and the executive function: The self as controlling agent. In A.
Kruglanski & E.T. Higgins (Eds.), Social psychology: Handbook
of basic principles (2nd ed., pp. 516–539). New York: Guilford. A
recent and thorough overview of the research in a broad context.
Gailliot, M.T., Baumeister, R.F., DeWall, C.N., Maner, J.K., Plant, E.A.,
& Tice, D.M. et al. (2007). (See References). Reports experiments
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Baumeister, R.F., Gailliot, M., DeWall, C.N., & Oaten, M. (2006). (See
References). Anoverviewof the research programon self-control with
emphasis on personality implications and alternative explanations.
Acknowledgments—The authors gratefully acknowledge re-
search support from the Templeton Foundation.
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Roy F. Baumeister, Kathleen D. Vohs, and Dianne M. Tice