Unpredictability and uncertainty in anxiety: a new direction for
emotional timing research
Jessica I. Lake1,2* and Kevin S. LaBar1,2
1 Center for Cognitive Neuroscience, Duke University, Durham, NC, USA
2 Department of Psychology and Neuroscience, Duke University, Durham, NC, USA
Interest in the relationship between emo-
tion and time perception has noticeably
increased in the past few years (Buhusi and
Meck, 2005; Droit-Volet and Meck, 2007;
Craig, 2009; Droit-Volet et al., 2011). Most
of this recent work has used emotional
stimuli, such as faces (e.g., Droit-Volet
et al., 2004; Tipples, 2008), pictures (e.g.,
Angrilli et al., 1997; Grommet et al., 2011),
and sounds (e.g., Noulhaine et al., 2007) to
understand how emotion can change the
subjective experience of short intervals of
time. Efforts have largely focused on deter-
mining what these findings reveal about
how time can be distorted and identifying
the mechanisms responsible for flexibly
modulating these distortions. In this issue,
Schirmer (2011) reviews various theories
that attempt to explain the mechanisms
underlying emotional influences on time
perception and proposes a hybrid theory to
better support findings in the field. Further
research will be necessary to support or con-
tradict the proposed mechanistic influences
of emotion on timing. While the value of
this work is clear, it is equally important
to address how timing research can inform
affective science and affective disorders,
a question that has thus far received little
attention within the field. Specifically, a
better understanding of how time is per-
ceived in anxiety-provoking contexts could
be important in fully appreciating the pro-
cesses underlying the experience of anxiety.
Many of the first studies of time per-
ception and anxiety analyzed estimates
of elapsed time under stressful conditions
(e.g., Langer et al., 1961; Hare, 1963; Watts
and Sharrock, 1984; Loftus et al., 1987).
While these studies consistently reported
overestimation of time and were ecologi-
cally relevant, they were limited in that they
relied on small numbers of trials and ret-
rospective reports, which have been argued
to reflect memory, rather than timing, pro-
cesses per se (Zakay, 1990). Using standard-
ized emotional stimuli such as pictures and
film clips, more recent studies have added
support to the idea that increased fear and
anxiety are correlated with the overesti-
mation of time intervals (e.g., Droit-Volet
et al., 2011; Grommet et al., 2011). At the
same time, recent work on anxiety and
related disorders has focused on the role of
ambiguity (e.g., Nader and Balleine, 2007;
Shankman et al., 2011; Zweifel et al., 2011).
Using work on timing and time perception
to address the influence of ambiguity on
anxiety could provide a unique perspective
from which to further advance our under-
standing of these clinical disorders.
Anxiety is defined as a state of prolonged
fear or arousal in response to a threat that is
ambiguous or unspecific (Lang et al., 2000).
Ambiguity refers to a situation or context in
which a threat may take various forms, and
different predictions and behaviors based on
these predictions may subsequently occur
(Whalen, 1998). Temporal unpredictability
(ambiguity in when an event will occur) and
probabilistic uncertainty (ambiguity in how
likely an event is to occur) are two types of
threat ambiguity. Human and non-human
animal studies suggest that both unpredict-
ability and uncertainty modulate anxiety-
like behaviors and activity in brain regions
associated with anxiety (Hsu et al., 2005;
Rosen and Donley, 2006; Herry et al., 2007).
Most studies showing an increase in
anxiety associated with temporal unpredict-
ability have used paradigms involving antic-
ipation of negative emotional events (e.g.,
Grillon et al., 2006). Note that this approach
contrasts with typical time perception stud-
ies in which emotion is manipulated pha-
sically through alterations in the sensory
features of a stimulus whose duration is
to be timed. In Grillon et al. (2004), anxi-
ety was operationally defined as the mag-
nitude of a startle response (Brown et al.,
1951) during cue-free periods within an
aversive conditioning paradigm (context-
potentiated startle). Context-potentiated
startle was greater when surrounding cues
were not predictive of when aversive events
occurred (i.e., aversive events were perceived
as occurring randomly) compared to cue-
free periods within the context of cues that
reliably predicted the temporal occurrence
of aversive events. Simply cuing previously
unpredictable shocks also reduces context-
potentiated startle responses (Fonteyne
et al., 2010). Together, these findings suggest
that temporal unpredictability increases
anxiety levels. The aversive nature of unpre-
dictability is further supported by studies
showing that animals prefer to receive pre-
dictable over unpredictable shocks (Gliner,
1972; Badia et al., 1979). Unpredictability
on its own (i.e., without an explicit associa-
tion with an aversive stimulus) may also be
anxiogenic. In a translational study examin-
ing both a mouse model and healthy human
participants, Herry et al. (2007) found that
manipulating the unpredictability of neu-
tral tones increased anxiety-like behaviors.
Furthermore, this study implicated the
amygdala, a structure commonly associ-
ated with fear and anxiety (e.g., LaBar et al.,
1998; Davis et al., 2010; Tye et al., 2011), in
the monitoring of unpredictability. Across
species evidence of sustained activity in
the amygdala was interpreted as reflecting
modified habituation processes to allow
individuals to remain prepared for action
in the face of unpredictability.
In addition to temporal unpredictabil-
ity, probabilistic uncertainty also seems to
modulate anxiety. While different relation-
ships between the probability of aversive
events and anxiety have been proposed
when those probabilities are known to the
subject (e.g., Epstein and Roupenian, 1970;
Bankart and Elliott, 1974; Loewenstein
et al., 2001), increased anxiety levels are
evident when subjects are unaware of
event contingencies. Sarinopoulos et al.
(2010) found that, in retrospective esti-
mates, healthy participants overestimated
how often a cue that ambiguously predicted
negative stimuli (50% chance of negative
Frontiers in Integrative Neuroscience www.frontiersin.org September 2011 | Volume 5 | Article 55 | 1
published: 19 September 2011
adolescent GAD patients with high intol-
erance of uncertainty (IU) scores showed
greater activity in the amygdala than controls
when contrasting “pure” uncertainty (50%
probability of a correct response) with other
task conditions. These patients also rated the
50% probability condition as more anxiety-
provoking than control participants. IU is
believed to correlate with worry (Dugas
et al., 1997), a characteristic feature of GAD,
according to the Diagnostic and Statistical
Manual of Mental Disorders – 4th edn
(American Psychiatric Association, 1994).
Interestingly, while IU may be positively
correlated with probabilistic uncertainty, it
was found to be negatively correlated with
context-potentiated startle responses in a
temporally unpredictable context (Nelson
and Shankman, 2011). College students with
higher IU scores showed decreased context-
potentiated startle responses. Because high
IU scores are associated with GAD, this
supports Grillon et al. (2009) and the idea
that GAD is not associated with increased
context-potentiated startle during tempo-
ral unpredictability. Probabilistic uncer-
tainty and temporal unpredictability may,
therefore, differentially modulate anxiety
and distinguish different anxiety-related
disorders. Further work with these clinical
populations is necessary and could have
important implications for nosology and
While studies have demonstrated time
distortions in non-anxious patient popula-
tions (Meck, 1996, 2005; Berlin and Rolls,
2004; Melgire et al., 2005; Penney et al., 2005;
Allman and Meck, 2011), examinations of
how time may be distorted in individuals
with anxiety disorders are lacking. It is likely
that time is distorted to a greater extent dur-
ing periods of increased threat and anxiety
in clinical populations suffering from anxi-
ety disorders than in healthy controls. It is
also predicted, based on current research on
unpredictability and uncertainty, that these
two forms of threat ambiguity may differ-
entially influence time distortions across
clinical groups and could help further
characterize the differences between certain
anxiety-related populations. For example,
panic and post-traumatic stress disorder
patients might show greater time distor-
tions resulting from unpredictable stimuli,
whereas GAD patients might show greater
distortions resulting from probabilistic
uncertainty. Such findings would indicate
of the aversive event resulted in an even
greater overestimation of time. These find-
ings suggest that the magnitude of time
distortion was correlated with the degree
of anticipatory anxiety experienced by the
participants. In this study, the cues pre-
dicting an aversive event were always tem-
porally predictable and 100% reinforced.
Manipulating unpredictability and uncer-
tainty in a similar paradigm by varying the
anticipation period within participants or
altering reinforcement probabilities could
reveal more about the relationship between
anxiety and time. If unpredictability and
uncertainty increase aversiveness (Herry
et al., 2007; Sarinopoulos et al., 2010), it may
be predicted that these anxiety-provoking
contexts would also increase distortions of
While the evidence provided above
implicates both temporal unpredictability
and probabilistic uncertainty in increased
anxiety, these two types of ambiguity may
be functionally dissociable across clinical
populations. Grillon et al. (2008) found
that panic disorder patients showed greater
context-potentiated startle in a temporally
unpredictable aversive condition compared
to a predictable condition with temporally
cued (but probabilistically uncertain) aver-
sive sounds. Similar results were found for
post-traumatic stress disorder patients using
a comparable study paradigm (Grillon et al.,
2009). The authors predicted these results
based on the idea that both disorders are
characterized by anxiety resulting from
the unpredictability of aversive events.
Interestingly, Grillon et al. (2009) found that
generalized anxiety disorder (GAD) patients
did not show the same pattern of anxiety-
like responses, suggesting that the anxiety
experienced by GAD patients might be qual-
itatively different. It is important to consider
that while the predictable condition in this
study was temporally invariant, a probabil-
istic reinforcement rate was used such that
the cue did not perfectly predict the aversive
stimulus. It is therefore possible that GAD
patients had an enhanced aversive response
to the probabilistic uncertainty associated
with this cue. Indeed, GAD patients showed
the highest context-potentiated startle in the
predictable condition, though this finding
was not statistically significant. The hypoth-
esis that GAD patients find probabilistic
uncertainty aversive is indirectly supported
by Krain et al. (2008), who found that
stimulus presentation following cue) was
followed by an aversive event. In this study,
increased activity in the amygdala and
insula was found during ambiguous cues
relative to cues that perfectly predicted
negative stimuli. The magnitude of this
difference was further correlated with the
degree of overestimation in retrospective
reports. Ambiguous cues are also associated
with increased skin conductance responses
(Grupe and Nitschke, 2011). These results
suggest that, like unpredictability, individ-
uals find uncertain probabilities aversive.
Neuroeconomic studies have also provided
evidence supporting the role of the amyg-
dala (e.g., Hsu et al., 2005) and insula (e.g.,
Preuschoff et al., 2008) in the processing of
decisions under uncertainty.
While time perception research has
shown that subjective time is sensitive to
fear and anxiety (e.g., Campbell and Bryant,
2007; Bar-Haim et al., 2010), there is a pau-
city of research directly addressing the func-
tion of ambiguity in time distortions. Based
on the work cited above showing that anxi-
ety is influenced by different types of ambi-
guity, we predict that the experience of time
may also be sensitive to manipulations of
threat ambiguity and, specifically of interest
here, to manipulations of unpredictability
and uncertainty. Fearful and angry faces,
which are both considered social indicators
of threat, tend to be overestimated in time
(Droit-Volet et al., 2004; Bar-Haim et al.,
2010; Tipples, 2011, but see Tipples, 2008).
Temporal overestimation of fearful faces is
further modulated by individual differences
in trait anxiety (Bar-Haim et al., 2010, but
see Tipples, 2011). The overestimation of
fearful faces is particularly relevant in con-
sidering the influence of ambiguity on time
perception. Whalen (1998) proposed that
fearful facial expressions are ambiguous
stimuli in experimental designs because the
source of threat resulting in the expressed
fear is unknown to participants. Findings
indicating that fearful faces increase time
estimates therefore provide preliminary
support for the idea that threat ambiguity
can influence time perception.
In Droit-Volet et al. (2010), partici-
pants judged a probe duration that began
after a neutral cue or a cue that predicted
an aversive event. Probe durations were
overestimated following the threat cue
compared to the neutral cue and a longer
anticipation period prior to the delivery
Lake and LaBar Anxiety and time perception
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topics in the field of emotion to increase
the value and applicability of time percep-
This work was supported by a National
Science Foundation Graduate Fellowship
to Jessica I. Lake.
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that time perception is intimately related to
the way in which anxiety is experienced and
how individuals respond to aversive events.
Taking this idea a step further, the
hypothesis that time distortions are yoked to
the experience of anxiety could potentially
open the door to new therapies focused on
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provides preliminary evidence that pay-
ing attention to time rather than emotion
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of emotion regulation. Future work could
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be critical for distortions in timing arising
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2011). Research showing that these brain
regions mediate the effects of unpredict-
ability and uncertainty on time distortions
would help in better understanding the bio-
logical mechanisms underlying the experi-
ence of anxiety.
It is suggested here that researchers in the
field of timing and time perception consider
how the study of emotional timing may
benefit not just the field of time perception,
but that of emotion and affective disorders
as well. Addressing the influence of ambi-
guity on anxiety and how different aspects
of ambiguity interact with time perception
could help improve our understanding of
the mechanisms underlying the experience
of anxiety, how these processes become
impaired in clinical populations, and poten-
tial treatment avenues (Meck et al., 2008;
Allman and Meck, 2011; Coull et al., 2011;
Gu et al., 2011). While the present paper
only addresses the potential influence of
unpredictability and uncertainty on time
Lake and LaBar Anxiety and time perception
Frontiers in Integrative Neuroscience www.frontiersin.org September 2011 | Volume 5 | Article 55 | 3
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lished online: 19 September 2011.
Citation: Lake JI and LaBar KS (2011) Unpredictability
and uncertainty in anxiety: a new direction for emotional
timing research. Front. Integr. Neurosci. 5:55. doi: 10.3389/
Copyright © 2011 Lake and LaBar. This is an open-access
article subject to a non-exclusive license between the authors
and Frontiers Media SA, which permits use, distribution
and reproduction in other forums, provided the original
authors and source are credited and other Frontiers condi-
tions are complied with.
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