2014. Vol.5, No.1, 1-5
Published Online January 2014 in SciRes (
Ego Depletion After Social Interference
Alex Bertrams1, Sabine Pahl2
1Department of Psychology, U niversity of Mannhe im, Mannheim, Germany
2School of Psy chology, University of Plymouth, Plymouth, UK
Received November 11th, 2013; revised December 9th, 2013; accepted January 2nd, 2014
Copyright © 2014 Alex Bertrams, Sabine Pahl. This is an open access article distributed under the Creative
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The present study examines whether social interference (i.e., interference with one’s goal attainment by
the bodily presence of others) depletes the limited resource of self-control strength. In an experimental
laboratory study (N = 34), half the participants experienced social interference whereas the other half did
not experience social interference by two confederates during a dexterity task. Afterwards, we measured
participants’ momentary self-control strength applying a Stroop colour-naming task. In line with our pre-
diction, participants’ performance in the Stroop task indicated that social interference reduced self-control
strength. We discuss implications for crowding research and crowding in natural settings.
Keywords: Crowding; Ego Depletion; Self-Control; Self-Regulation
The presence of other people frequently interferes with indi-
vidual goals: In crowded pedestrian zones, other people may
walk in front, stand in the way, or walk across one’s projected
path; in busy supermarkets, other people may block access to
shelves containing desired goods. When this happens, individu-
als are forced to coordinate their own movement with that of
others, make avoidance movements, adjust their speed, or wait.
This may be exhausting, especially when it interferes with the
completion of goals (e.g., keeping an appointment or quickly
doing the shopping). The present research aims to show that
adaptation to such social interference is associated with self-
regulatory costs. We assume that social interference requires
self-control and, therefore, depletes the resource underlying
self-control, which in turn is expected to lead to reduced per-
formance in subsequent self-control demands.
Our conceptualisation of social interference is based on
Schopler and Stockdale’s (1977) definition of social interfer-
ence in crowding: “The presence of others is interfering when-
ever they restrict, disrupt, or block goal-oriented response se-
quences” (p. 82). Emanating from this early definition, in the
present work we perceive social interference as an immediate
interference with a person’s goal attainment by the bodily
presence of other persons. In particular, we focus on the case in
which others physically block individuals’ moving paths with
their bodies, thereby impairing individuals in moving from
place A to place B (i.e., attainment of a physical goal). Such
interference with a physical goal may often be related to inter-
ference with a psychological goal; for instance, when a person
who is in a hurry to keep an important appointment is slowed
down by others in a crowded pedestrian zone. Social interfer-
ence, as we conceptualise it, is primarily characterised by
physical interaction in contrast to psychological interaction:
Someone can block another person’s way (physical interaction)
without noticing it, so that communication between the two
persons (psychological interaction) does not take place. Par-
ticularly in cities, social interference may be an integral part of
everyday life (e.g., in pedestrian zones, in shops, and in railway
We offer a new perspective to the phenomenon of social in-
terference by analysing it in light of an established self-control
model (Baumeister, Vohs, & Tice, 2007; Muraven & Baumeis-
ter, 2000). Self-control means the overriding, or inhibition, of
one’s own automatic, habitual, or innate behavioural tendencies
in order to pursue long-term goals or to act in line with stan-
dards such as social norms (e.g., Baumeister et al., 2007; Mu-
raven & Baumeister, 2000). In other words, self-control enables
people to alter their predominant responses in service of higher
goals instead of acting on the spur of the moment. For instance,
if a person’s goal is to lose weight (a higher goal), that person
has to suppress naturally occurring eating impulses (self-con-
trol). Lack of self-control implies impulsive behaviour (e.g.,
eating chocolate) and impedes longer term goal fulfilment (e.g.,
losing weight).
In the past years, a strength model explaining when and why
self-control succeeds or fails has received a great deal of atten-
tion and has been empirically confirmed in various experiments
(for reviews, see Baumeister, 2002; Baumeister et al., 2007;
Muraven & Baumeister, 2000). According to the strength
model of self-control, exertion of self-control depletes a limit ed
strength resource required for the successful exertion of self-
control. Therefore, individuals who have recently used this
resource subsequently have less self-control strength available
(a state coined ego depletion) compared to individuals who
have not recently exerted self-control; thus, the former are less
successful in exerting self-control than the latter. Potential al-
ternative explanations, such as differences in mood or self-
efficacy, do not seem to be responsible for this depletion effect
(Muraven, Tice, & Baumeister, 1998; Wallace & Baumeister,
2002). An important aspect of the strength model is that differ-
ent kinds of self-control are assumed to rely on the same
strength resource, even if the required behaviours are in widely
different domains. For instance, participants who were asked to
suppress a certain thought were subsequently less successful in
suppressing their emotional expressions compared to partici-
pants who were not initially asked to control their thoughts
(Muraven et al., 1998: Study 3). Experimentally varying the
self-control demands for participants in an initial task and then
assessing participants’ self-control performance in a second
task has become the basic approach for the examination of the
determinants and consequences of momentarily available self-
control strength (Baumeister et al., 2007).
Although initially focusing on intra-personal events, several
studies in the last years have examined how interpersonal
events affect self-control. Some of these studies examined the
effects of a lack of social interaction. For instance, Baumeister,
DeWall, Ciarocco, and Twenge (2005) found that social exclu-
sion caused decrements in self-control. In their study, people
who were informed that no one wanted to work with them later
ate twice as many chocolate cookies than participants who had
not been rejected. However, the other extreme of social interac-
tion—too much contact or input, such as the kind of social in-
terference we experience in shopping malls or in crowded pe-
destrian zones—might also have detrimental effects on self-
Much earlier, Glass and Singer (1972) came up with the idea
that adaptation to the physical environment can have “psychic
costs”. In their laboratory experiments, participants who were
exposed to uncontrollable noise showed decreased performance
in subsequent tasks that were akin to current measures of
self-control (e.g., persistence and overriding of impulses to quit
during a frustrating task; see Baumeister et al., 2007). Glass and
Singer interpreted their results as evidence that adaptation to
uncontrollable circumstances requires psychic resources that
will be missing in subsequent tasks. This interpretation is in
line with the more recent strength model of self-control (Bau-
meister et al., 2007; Muraven & Baumeister, 2000), in which
such psychic costs are referred to as depleted self-control
strength. Similar to the noise in Glass and Singer’s work, social
interference may be seen as uncontrollable since normally it
may be difficult, if not impossible, to control how other persons
will move (e.g., in a shop or a pedestrian zone). Hence, we
assume that exposure to social interference, similar to exposure
to uncontrollable noise, will cause decrements in subsequent
self-control by depleting self-control strength.
But why is it that social interference supposedly impairs
self-control? In social interference situations, a person’s goal-
directed movements are interfered with and, therefore, need to
be adjusted. This adjustment involves the overriding of origi-
nally intended responses (i.e., self-control), such as altering
intended movements (deviating from the direct path, slowing
one’s movements down) or suppressing intended movements
(waiting) in order to avoid colliding with other persons. Thus,
exposure to social interference should tax the limited resource
of self-control strength, which should result in less self-control
strength for later use. If people faced with social interference
did not exert self-control by adjusting their movements, quite
often they would find themselves in violation of social norms
(e.g., colliding with others), which is generally undesirable.
Indirect evidence that social interference may impair self-
control stems from Heller, Groff, and Solomon (1977). They
experimentally manipulated spatial density as well as the de-
mand to move about the lab while performing tasks, such as
sorting pages in a booklet and adding up numbers. When par-
ticipants were in a dense situation and had to move about to
perform the tasks (i.e., physical interaction was high and inter-
fered with the task goals), they showed decreased performance
during the tasks. One possible explanation of this finding might
be that dealing with social interference in this condition de-
pleted participants’ self-control strength, which, as a result,
negatively affected their self-control of thoughts and attention
(i.e., concentration; see Baumeister, Heatherton, & Tice, 1994).
However, no direct evidence of this explanation is available to
date. In a fie ld study along t he lines of Hel ler et al.’s labor atory
experiment, Langer and Saegert (1977) asked participants to
move through a busy versus a non-busy department store while
performing a complex cognitive-behavioural task requiring
concentration. In relation to the comparison group, participants
who moved through the busy environment experienced more
people obstructing their way while they tried to perform the
task; that is, they experienced more social interference. These
participants also performed worse than the participants in the
comparison group. Again, one potential explanation for the
lowered performance might be that dealing with the demands of
social interference led to depletion of self-control strength.
Although Heller et al.’s (1977) as well as Langer and Sae-
gert’s (1977) findings are compatible with our assumption that
social interference has adverse effects on self-control, they do
not constitute sufficient evidence. Because the tasks were per-
formed during the experience of social interference in suppos-
edly highly sensory-demanding environments, increased cogni-
tive load rather than reduced self-control strength might have
impaired performance in these tasks. Theoretically, a key dif-
ference between the self-control model and cognitive capacity
models is that self-control depletion lasts beyond the situation
and can be measured after the concurrent cognitive demands
have ceased (Muraven et al., 1998). Therefore, it would be
desirable to test whether effects on task performance last even
after the social interaction. There is one set of studies that has
applied the strength model of self-control to test the af-
ter-effects of social interactions (Finkel et al., 2006). Finkel et
al. found that poorly coordinated interactions that required ad-
ditional adjustment beyond the actual task participants were
working on with a confederate subsequently caused poorer
self-control. However, this study examined interaction tasks
jointly performed by two individuals (e.g., entering data to-
gether, navigating a computer maze) rather than the effects of
physical blocking outside of direct interactions. Thus, Finkel et
al. examined a kind of social interaction quite different from
our conceptualisation of social interference. We focus more on
the observation that people are also moving objects in space
and that, as such, they can block one others’ paths.
In sum, there is evidence that adaptation to an uncontrollable
physical environment (here: uncontrollable noise) subsequently
leads to poorer self-control (Glass & Singer, 1972), that social
interference has detrimental effects on performance in tasks that
involve self-control (Heller et al., 1977; Langer & Saegert,
1977), and that social interactions which require adjustment
impair subsequent self-control by reducing self-control strength
(Finkel et al., 2006). Up to now, however, no study exists that
has shown detrimental effects of social interference on self-
control after the interference situation has ended, thus ruling out
a cognitive capacity explanation. So, in the present study, we
aimed to directly test the hypothesis of whether social interfer-
ence depletes self-control strength.
We conducted an experimental laboratory study in which
participants engaged in a task (filling a jug with water using a
spoon) while experiencing or not experiencing social interfer-
ence through two confederates. Afterwards, we used response
latencies in a Stroop task (Stroop, 1935) to measure momentar-
ily available self-control strength, as in previous studies (e.g.,
Richeson & Shelton, 2003): Participants were asked to name
the print colours of non-corresponding colour words (e.g., the
word BLUE printed in yellow). This requires participants to
suppress the highly automated response to read the words and
replace it by naming the printed colours instead; that is, par-
ticipants have to exert self-control. Performance in the Stroop
task should therefore be impaired if self-control strength has
previously been depleted. We expected that participants in the
social interference condition would have longer response laten-
cies for completing the Stroop task than participants in the con-
trol condition who had not experienced social interference. This
pattern would indicate that dealing with social interference has
costs in terms of the depletion of self-control strength.
Participants and Design
The sample included 34 undergraduates enrolled at a univer-
sity in Southern Germany (28 females, mean age = 23.8). We
excluded three additional participants from analyses who ex-
pressed severe doubts about the cover story and one who exhib-
ited extremely low motivation to follow the instructions (re-
ported by the confederates and the participant himself); how-
ever, the same pattern of results emerged when these partici-
pants were included. All students participated voluntarily and
received chocolate as a reward. The participants were randomly
assigned to two conditions: In the experimental condition (n =
18), their movements were systematically obstructed by two
female confederates (social interference); in the control condi-
tion (n = 16), their movements were not obstructed (no social
Materials and Procedure
The students were asked to participate in a study concerning
the interplay between cognition and coordination. Participants
were tested individually (together with the t wo confederates) in
sessions lasting approximately twenty minutes. Upon arrival to
the laboratory, participants were told that the study involved
groups of three people. The confederates were placed standing
in different corners of the room and appeared to be unknown to
each other (one was looking through her diary; the other was
busy with her mobile phone).
Next the experimenter presented the cover story, which
stated that recent neuropsychological studies had found close
connections between brain a reas responsible for body c oordina-
tion and fluid intelligence, and that this relation could be tested
using behavioural measures. Ostensibly, a formula had been
developed to assess fluid intelligence through performance in
an unpractised dexterity ta sk, with the ai m of collecti ng data on
this relation. The experimenter emphasised the importance of
fluid intelligence for academic success in order to make the task
more relevant for the participants.
After this, the task was explained. Participant and confeder-
ates were instructed to fill a spoon with water at a sink within
the laboratory room and to balance until its contents were de-
livered to an individually assigned jug. They were told to repeat
this procedure until the experimenter returned. The experi-
menter pointed out that the amount of water in the jug would
become the numerical value to be entered into the fluid intelli-
gence formula (a measuring container and a funnel were visibly
placed in the room). Participant and confederates were also
instructed not to speak during the task (cf. Heller et al., 1977).
After the instructions, the experimenter gave the start signal and
immediately left the room. The reason why the experimenter
was not present during this phase of the experiment was to give
participants in the social interference condition no possibility to
complain to the experimenter (e.g., about the confederates’
The manipulation of the independent variable took place
during the dexterity task. The direct path between sink and jugs
was narrow due to tables standing sideways, allowing only one
person through at a time. In the social interference condition,
the confederates used this path exclusively so that the fastest
way was systematically obstructed for the participant, forcing
the participant to regularly adjust his or her movement (i.e.,
stop and wait, step aside). Furthermore, the confederates posi-
tioned themselves near the sink at the beginning of the task.
Therefore, the confederates were faster to the sink than the
participant for the first time they filled their spoons; as a con-
sequence, the participant’s access to the sink was frequently
blocked during the course of the task, so that the participant had
to repeatedly interrupt the intended goal-directed movement
and wait. In contrast, in the control condition the confederates
took a longer route around the tables so that they did not inter-
fere with the participant’s movements. In addition, they surrep-
titiously arranged their speed so that they arrived at the sink
after the participant; thus, the participant did not have to wait.
After five minutes, the experimenter returned and interrupted
the activity. The experimenter announced that another measure
had to be taken individually and asked the participant to be
tested first. The confederates were asked to wait in a room next
to the lab. The participant then received 280 incongruent Stroop
stimuli on paper (i.e. the word did not correspond to the colour
in which it was printed, e.g., the word BLUE was printed in
yellow). We used blue, green, red, and yellow as colour words
as well as print colours. This task was introduced to the par-
ticipant as a measure of mental flexibility and the participant
was instructed to name aloud the print colours of the words as
fast as possible while avoiding any mistakes. The time the par-
ticipant took to name all Stroop stimuli and the number of mis-
takes made was recorded by the experimenter.
Afterwards, the participant rated the perceived interference
during the dexterity task on two items (“How much did the
other participants obstruct you with attaining the task goal?”,
“How often were the other participants standing in your way?”).
On one-item measures, they also rated the amount of effort
invested in the dexterity task as well as in the Stroop task, the
personal importance of performing well in each of these tasks,
the amount of frustration that was experienced during the dex-
terity task, and the extent of negative feelings that were experi-
enced towards the confederates. All these ratings were made on
7-point Likert scales. Finally, the participants were thanked,
probed for suspicion, rewarded, and debriefed. Also each con-
federate rated on one-item measures how much the participant
was obstructed as well as how motivated, how frustrated, and
how aggressive the participant appeared during the dexterity
task on 6-point Likert scales. Participant and confederate rat-
ings were coded such that higher scores indicated higher values
of the respective variable. The confederates’ ratings for each
participant were averaged across b oth confederates.
Manipulation Chec k
For the comparisons of means between the two experimental
groups, we applied independent-samples t-tests. Since the par-
ticipants’ two ratings on perceived interference were highly
correlated, r = .83, p < .001, we averaged them. Both partici-
pants (M = 5.11, SD = 1.55 vs. M = 2.56, SD = 1.46), t(32) =
4.92, p < .001, d = 1.69 and confederates (M = 5.61, SD = 0.74
vs. M = 1.22, SD = 0.26), t(32) = 22.57, p < .001, d = 7.73 re-
ported more perceived social interference in the social interfer-
ence condition than in the control condition. Participants also
transported less water to the jug in the social interference con-
dition than in the control condition (M = 83.17 ml, SD = 15.50
vs. M = 153.88 ml, SD = 28.22), t(32) = 9.20, p < .001, d =
3.16. Altogether, these findings indicate that the social inter-
ference manipulation was successful.
Stroop Performance
We conducted an independent-samples t-test with the ex-
perimental condition (social interference vs. no social interfer-
ence) as an independent variable and time required for com-
pleting the Stroop task as a dependent variable. As expected,
participants who had experienced social interference during the
dexterity task took statistically significantly longer in the
Stroop task (M = 310.28 s, SD = 59.75 s) than participants who
had not experienced social interference (M = 264.88 s, SD =
40.53 s), t(32) = 2.56, p = .02, d = 0.88. Participants in the so-
cial interference condition took, on average, 45 sec. longer to
complete the Stroop task than participants in the control condi-
tion without social interference. The number of errors made in
the Stroop task did not differ between conditions, t(32) < 1.
Thus, a speed-accuracy trade-off cannot account for the finding
on time required for completing the Stroop task.
Supplementary Analyses
There were no differences between experimental conditions
regarding participants’ ratings of invested effort and importance
of performance in the dexterity task or in the Stroop task, and
the confederate ratings of participants’ motivation or aggression
during the dexterity task (ps > .25). Ratings of the personal
importance of performance in the dexterity task were high (M =
6.00, SD = 0.84 in the social interference condition; M = 6.06,
SD = 0.93 in the no social interference condition; maximum
possible score = 7.00), indicating that participants in both ex-
perimental conditions were motivated to achieve the goal dur-
ing the dexterity task.
Participants in the social interference condition did not rate
the dexterity task as being more frustrating than did participants
in the control condition, t(32) < 1. However, the confederates
perceived the participants in the social interference condition as
more frustrated (M = 1.47, SD = 0.70) than the participants in
the control condition (M = 1.03, SD = 0.13), t(32) = 2.50, p
= .02, d = 0.85. Moreover, participants in the social interference
condition tended to report more negative feelings towards the
confederates (M = 3.22, SD = 1.70) than did participants in the
control condition (M = 2.31, SD = 1.35), t(32) = 1.71, p = .10, d
= 0.59. Neither participants’ frustration as perceived by the
confederates, r = .17, p = .34, nor participants’ negative feel-
ings towards the confederates r = .01, p = .94 correlated with
the time participants took to complete the Stroop task. Thus, the
performance decrements in the social interference condition
were not attributable to these variables.
The present research aimed to demonstrate that exposure to
social interference reduces self-control strength and, hence,
impairs subsequent self-control. In our study, the goal-directed
movements of one group of participants were obstructed by the
physical presence of two confederates (i.e., social interference),
forcing them to adjust their intended movements. Such adjust-
ment was assumed to involve self-control and to consume
self-control strength that would subsequently be lacking in later
self-control demands. We found that participants who experi-
enced this social interference during a dexterity task took
longer in a subsequent Stroop colour-naming task than partici-
pants who did not experience social interference. This finding
was not attributable to a speed-accuracy trade-off as well as
participants’ task motivation, feelings of frustration, or negative
affect towards the confederates. Since response latencies in the
Stroop task have been shown to depend on self-control strength
(e.g., Richeson & Shelton, 2003), our study provides initial
evidence for the assumption that social interference draws on
the resource necessary for successful self-control, indicating
that exposure to social interference can cause decrements in
self-control .
On the one hand, our findings may provide a novel theoreti-
cal explanation of crowding effects. Prior to our study, no direct
evidence was available that self-control might be taxed by
crowding. Since social interference has been argued to be cen-
tral in crowding (Schopler & Stockdale, 1977), the present
findings suggest that it may be worthwhile to investigate
self-control processes further, as an explanation of observed
effects of crowding. As we have already mentioned in the intro-
duction, Heller et al.’s (1977) as well as Langer and Saegert’s
(1977) findings on reduced ta sk performance in crowded situa-
tions may, at least in part, be determined by diminished self-
control strength stemming from exposure to social interference.
Further evidence that effects of crowding may be attributed to
reduced self-control strength comes from studies on helping
behaviour: A recent study that was theoretically based on the
strength model of self-control demonstrated that initial deple-
tion of self-control strength subsequently decreased participants’
willingness to help others (DeWall, Baumeister, Gailliot, &
Maner, 2008). This corresponds to a finding in the crowding
literature that participants who had experienced a crowded
situation were less helpful to someone in need than were par-
ticipants who had experienced a less crowded situation (Cohen
& Spacapan, 1978).
On the other hand, the present research extends self-control
research, particularly with reference to the important questions
of why and when people fail in self-control. Extending eviden-
ce on the adverse effects on self-control after social exclusion
(Baumeister et al., 2005), positive self-presentation (Vohs, Bau-
meister, & Ciarocco, 2005), or poorly coordinated dyadic con-
versation (Finkel et al., 2006), social interference seems to tax
self-control resources as well. So, our study provides a new pie-
ce to the mosaic that makes up the costly demands of social life.
One central limitation of the present study is its lack of ex-
ternal validity, which is typical for laboratory experiments.
Participants were confronted with an artificial setting that was
different from natural situations in which social interference
may occur. Therefore it cannot be excluded that the decrement
in Stroop performance was caused by characteristics specific to
the circumstances in our investigation. It might be possible, for
instance, that the adjustment of movements is much more
automatic in natural settings, such as in a pedestrian zone, than
during an unfamiliar dexterity task in a lab room. That is, since
exertion of automatic behaviours should not require self-control
(Muraven & Baumeister, 2000), social interference would not
lead to diminished self-control strength outside the laboratory.
However, the field study by Langer and Saegert (1977) we
mentioned in the introduction indicates that social interference
can impair performance in complex tasks, even in natural set-
tings. Although Langer and Saegert’s study does not provide
sufficient evidence to confirm our specific self-control hypo-
thesis, it gives us some confidence that social interference may
have adverse after-effects on self-control in real-life situations.
Still, one important avenue for future research when following
up on our initial findings would be to apply the present ap-
proach to more natural settings.
What implications can be drawn from the results? Basi-
cally, after the experience of social interference, people should
be more likely to fail in self-control. There are numerous ex-
amples in every-day life in which this may matter. For instance,
exposure to social interference in a shopping mall could poten-
tially lead to impulse buying. Vohs and Faber (2007) demon-
strated that participants whose self-control strength had recently
been depleted felt stronger urges to buy, were willing to spend
more money, and actually spent more money compared to par-
ticipant whose self-control strength was intact. Hence, crowded
shopping malls, in which social interference is quite likely to
occur, might contribute to higher spending. Since the ability to
resist other temptations such as delicious but unhealthy food
(Baumeister, Bratslavsky, Muraven, & Tice, 1998) or alcohol
(Muraven, Collins, & Nienhaus, 2002) also relies on the mo-
mentary availability of self-control strength, people are sup-
posed to be more likely to give in to these temptations after
social interference. Many temptations (e.g., fast food, candies,
beer) are easily available in pedestrian zones and shopping
malls, and unfortunately these places are frequently crowded.
Future research could also try to expand the scope of the social
interference–self-control relationship to traffic congestion. In
key aspects, driving a car through the city during rush hour
provides a similar interference situation as in the present re-
search: Paths and goals are blocked and movements of feet and
hands have to be adjusted. However, loss of self-control while
driving a car could have dangerous and potentially fatal conse-
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