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Ecological Momentary
Assessment
Saul Shiffman,
1
Arthur A. Stone,
2
and Michael R. Hufford
3
1
Department of Psychology, University of Pittsburgh, Pittsburgh, Pennsylvania
15260; email: Shiffman@pitt.edu
2
Psychiatry and Behavioral Sciences Department, State University of New York,
Stony Brook, Stony Brook, New York 11794-8790; email: Arthur.stone@sunysb.edu
3
Cypress Bioscience, Inc., San Diego, California 92121;
email: mhufford@cypressbio.com
Annu. Rev. Clin. Psychol. 2008. 4:1–32
First published online as a Review in Advance on
November 28, 2007
The Annual Review of Clinical Psychology is online
at http://clinpsy.annualreviews.org
This article’s doi:
10.1146/annurev.clinpsy.3.022806.091415
Copyright
c
2008 by Annual Reviews.
All rights reserved
1548-5943/08/0427-0001$20.00
Key Words
diary, experience sampling, real-time data capture
Abstract
Assessment in clinical psychology typically relies on global retro-
spective self-reports collected at research or clinic visits, which are
limited by recall bias and are not well suited to address how behav-
ior changes over time and across contexts. Ecological momentary
assessment (EMA) involves repeated sampling of subjects’ current
behaviors and experiences in real time, in subjects’ natural envi-
ronments. EMA aims to minimize recall bias, maximize ecological
validity, and allow study of microprocesses that influence behavior in
real-world contexts. EMA studies assess particular events in subjects’
lives or assess subjects at periodic intervals, often by random time
sampling, using technologies ranging from written diaries and tele-
phones to electronic diaries and physiological sensors. We discuss
the rationale for EMA, EMA designs, methodological and practical
issues, and comparisons of EMA and recall data. EMA holds unique
promise to advance the science and practice of clinical psychology
by shedding light on the dynamics of behavior in real-world settings.
1
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Contents
INTRODUCTION................. 2
WHAT IS ECOLOGICAL
MOMENTARY
ASSESSMENT? ................. 3
Momentary, Real-Time
Assessment.................... 4
Real-World Data ................. 4
Repeated Assessment ............. 4
ECOLOGICAL MOMENTARY
ASSESSMENT SCOPE
AND HISTORY ................. 5
Historical Roots .................. 6
AUTOBIOGRAPHICAL MEMORY
AND LIMITATIONS
OF RECALL .................... 7
THE USES OF ECOLOGICAL
MOMENTARY
ASSESSMENT .................. 8
Individual Differences ............ 8
Natural History .................. 8
Contextual Associations........... 9
Temporal Sequences .............. 9
DATA COMPARING
RETROSPECTIVE AND
REAL-TIME REPORTS......... 10
Comparison of Aggregated
Recall-Based Data
andEMA..................... 10
Correlations Between
Disaggregated EMA
and Recall..................... 11
Construct Validity of Real-Time
Versus Recall Assessments ..... 12
ECOLOGICAL MOMENTARY
ASSESSMENT DESIGNS
AND APPROACHES ............ 13
Event-Based Monitoring.......... 14
Time-Based Designs.............. 14
Combination Designs ............ 15
Use of Recall in EMA ............ 16
Sampling Versus Coverage
Strategies ..................... 16
Daily Diaries: A Special Case
ofEMA....................... 17
USE OF ECOLOGICAL
MOMENTARY ASSESSMENT
IN TREATMENT ............... 17
For Assessment................... 17
For Intervention ................. 18
MEASUREMENT
CONSIDERATIONS FOR
ECOLOGICAL MOMENTARY
ASSESSMENT
SELF-REPORTS ................ 19
METHODOLOGICAL
CONSIDERATIONS IN
ECOLOGICAL MOMENTARY
ASSESSMENT STUDIES ....... 20
Reactivity ........................ 20
Compliance ...................... 20
SPECIAL POPULATIONS ......... 22
ANALYSIS OF EMA DATA ......... 22
PRACTICAL ISSUES IN
ECOLOGICAL MOMENTARY
ASSESSMENT .................. 23
EMA Hardware and Software ..... 23
Other Practical Considerations.... 24
CONCLUSION .................... 24
INTRODUCTION
Clinical psychologists, along with behavioral,
social, and health scientists and practitioners
of every stripe, are interested in people’s ev-
eryday real-world behavior. This interest is
perhaps especially marked for clinical psy-
chologists because psychopathology and its
functional impairments are expressed in real-
world settings: No one is diagnosed or treated
because of how they behave in a laboratory
or consulting room. Yet, behavior is seldom
studied, assessed, or observed as it unfolds in
the real world. Instead, both clinicians and re-
searchers rely on global, summary, or retro-
spective self-reports of behavior: We ask pa-
tients how often they experience anxiety, on
2 Shiffman
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average, how many panic attacks they had dur-
ing the past week or month, how intense their
pain generally is during the day, or how de-
pressed their mood has been. Moreover, the
emphasis on global assessments can keep us
from seeing and studying dynamic changes
in behavior over time and across situations,
from appreciating how behavior varies, and is
governed, by context, and from understand-
ing cascades of behavior, or interactions with
others or with our environments that play out
as a sequence of events over time. Thus, our
frequent reliance on global, retrospective re-
ports seriously limits our ability to accurately
characterize, understand, and change behav-
ior in real-world settings and misses the dy-
namics of life as it is lived, day-to-day, hour by
hour. In this review, we discuss an alternative
to static retrospective reports—Ecological
Momentary Assessment (EMA, Stone &
Shiffman 1994), which allows subjects and pa-
tients to report repeatedly on their experi-
ences in real-time, in real-world settings, over
time and across contexts.
WHAT IS ECOLOGICAL
MOMENTARY ASSESSMENT?
EMA is not a single research method; it en-
compasses a range of methods and method-
ological traditions, which we discuss below.
However, to provide a quick sense of how
EMA can be used to inform our understand-
ing of clinical psychology, and as a reference
for its paradigmatic characteristics, we de-
scribe a prototypical EMA study. Our exam-
ple is a study of cigarette smoking cessation
and relapse (see Shiffman 2005). Smoking is a
good target for EMA, as it involves a behav-
ior with clearly discernible small-scale events.
Tracking experience over time allows the re-
search to track the process of quitting and re-
lapsing over time. In this study, smokers who
had recently quit were asked to monitor their
cigarette craving, nicotine withdrawal symp-
toms, mood, and activities over several weeks,
using palm-top computers as electronic di-
aries. Since episodes of smoking (“lapses”)
Ecological
Momentary
Assessment (EMA):
methods using
repeated collection
of real-time data on
subjects’ behavior
and experience in
their natural
environments
were of key interest, subjects were asked to
record any episodes of smoking as they hap-
pened, and were then prompted to complete
brief assessments of their craving, mood, and
activities during the episode. On top of this,
about five times each day, at random times, the
electronic diaries also prompted, or “beeped,”
subjects and administered a similar assess-
ment. These assessments captured not only
the events associated with lapses, but the flow
of mood, behavior, and events in the hours
and days before and after lapses.
These EMA data, captured using the
electronic diaries, allowed the investiga-
tors to answer a variety of questions (see
Shiffman 2005), including: How much crav-
ing do smokers experience when they quit
smoking? (Surprisingly little, except in dis-
crete episodes; Shiffman et al. 1997a.) Does
craving intensity vary with individual charac-
teristics, such as nicotine dependence? (Yes;
Shiffman et al. 2004.) Are day-to-day changes
in craving intensity associated with variations
in subsequent risk of smoking? (Yes, espe-
cially craving experienced first thing in the
morning; Shiffman et al. 1997a.) Does experi-
encing emotional distress predispose smokers
to lapse? (Yes, but only acute distress, over a
period of hours; Shiffman & Waters 2004.)
Do situational factors affect lapse risk? (Yes,
especially emotional distress, others smok-
ing, and alcohol consumption; Shiffman et al.
1996b.) Do lapses diminish self-efficacy? (Yes;
Shiffman et al. 1997b.)
These are just some of the kinds of ques-
tions and answers that can be examined using
EMA. They illustrate the potential for EMA
data to address questions about individual dif-
ferences, about particular episodes or situa-
tions, about the unfolding of processes over
time, and about the interactions among these
factors. In this way, they illustrate both the
richness and the complexity of EMA data.
This study illustrates several key fea-
tures common to EMA approaches (Stone &
Shiffman 1994, Stone et al. 2007a):
Data are collected in real-world envi-
ronments, as subjects go about their
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Autobiographical
memory: memory
processes involved in
recalling one’s own
experience
lives. This is the “ecological” aspect
of EMA and allows generalization to
the subjects’ real lives, i.e., ecological
validity.
Assessments focus on subjects’ current
state; for example, self-reports ask about
current feelings (or very recent ones),
rather than asking for recall or summary
over long periods. This is the “momen-
tary” aspect of EMA and aims to avoid
the error and bias associated with retro-
spection.
Moments are strategically selected for
assessment, whether based on particu-
lar features of interest (e.g., occasions
when subjects smoked), by random sam-
pling (to characterize subjects’ experi-
ences through representative sampling),
or by other sampling schemes.
Subjects complete multiple assessments
over time, providing a picture of how
their experiences and behavior varies
over time and across situations.
This study is only illustrative. The par-
ticular design, assessment schedule, assess-
ment content, and even technology will vary
across studies, depending on the behavior re-
searchers are studying, their aims, and their
theoretical frameworks. But what EMA stud-
ies have in common is the collection of as-
sessments of subjects’ current or recent states,
sampled repeatedly over time, in their natural
environments. With this illustration as back-
ground, we now move to highlighting the key
aspects of EMA methods.
Momentary, Real-Time Assessment
EMA methods developed in part in response
to the limitations of retrospective recall. Al-
though we all feel confident in our own mem-
ories, research on autobiographical memory
teaches us that memory can be quite un-
reliable (Bradburn et al. 1987, Tourangeau
2000). Our recollections are not just inac-
curate: They are often systematically biased.
That is, the errors made in recalling informa-
tion are not just random noise; rather, they
change the data in systematic ways. For ex-
ample, people are more likely to retrieve neg-
atively valenced information when they are in
a negative mood, thus introducing substantial
bias (Clark & Teasdale 1982). Because the dy-
namics of recall are so important to justifying
and structuring EMA methods, these issues
are reviewed in more detail below.
Real-World Data
If one is interested in how subjects feel at
work, there is no point asking them how they
feel in the research clinic—or at home, for
that matter. EMA recognizes that many be-
haviors and experiences can be affected by
context. Therefore, in order for assessed ex-
perience or behavior to be representative, it
has to be sampled in the contexts in which it
naturally occurs. Stated more simply, EMA
emphasizes ecologically valid observations.
Because EMA data are collected in sub-
jects’ natural environments—in real life—
they should be generalizable to real-world,
real-life experience.
Repeated Assessment
EMA studies involve many repeated mea-
sures, covering various extents of time with
varying intensity of assessment. Some imple-
ment a dense schedule of assessment, assessing
subjects as often as every 30 minutes (Shapiro
et al. 2002) over a period of days. At the other
extreme, subjects may be assessed less fre-
quently (e.g., daily) over periods as long as a
year ( Jamison et al. 2001). Some EMA stud-
ies are primarily focused on using these many
measures to characterize the subject’s “typi-
cal” state, aggregating over the repeated as-
sessments to better characterize the subject’s
average state across situations. More often,
EMA studies use the temporal resolution af-
forded by multiple measures to focus on the
within-subject changes in behavior and expe-
rience over time and across contexts, address-
ing how symptoms vary over time or how sit-
uational antecedents influence behavior.
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In summary, EMA aims to assess the ebb
and flow of experience and behavior over time,
capturing life as it is lived, moment to mo-
ment, hour to hour, day to day, as a way
of faithfully characterizing individuals and of
capturing the dynamics of experience and be-
havior over time and across settings.
ECOLOGICAL MOMENTARY
ASSESSMENT SCOPE
AND HISTORY
EMA is sometimes mistakenly associated nar-
rowly with particular designs, such as the
use of randomly scheduled prompts to col-
lect assessments, or with certain technolo-
gies, such as the use of palm-top comput-
ers. However, EMA is not a single method,
much less a particular technology, but rather
a collection of methods that share the charac-
teristics described above. EMA includes tra-
ditional diaries, whether they use paper and
pencil (Green et al. 2006), palm-top com-
puters (Shiffman et al. 1996b), or telephones
(Perrine et al. 1995). It encompasses inter-
personal interaction diaries (Reis & Wheeler
1991), ambulatory physiological monitoring
(Kop et al. 2001), and collection of medi-
cation compliance data by instrumented pill
bottles (Byerly et al. 2005). The technologies
differ, the targets of assessment differ, the
schedules of data collection differ, but all of
these methods focus on collecting data repeat-
edly, in close to real time, and in subjects’ nat-
ural environments. EMA aims to bring these
diverse methods under a common framework
in order to define higher-order methodologi-
cal principles, identify commonalities across
methods, and thus provide a framework in
which researchers and clinicians can select the
appropriate methods for their particular re-
search studies or interventions.
Although the term “EMA” was only coined
in 1994 (Stone & Shiffman 1994), EMA re-
search, as defined here, has been an active area
for decades. A search using the terms “diary,”
“experience sampling,” and “ecological mo-
mentary assessment” yielded over 3000 cita-
tions in the past 25 years on PsychLit, and
196,000 “hits” on Google
TM
Scholar. This in-
dicates a substantial volume of research activ-
ity using EMA methods.
The emergence of EMA as an important
research method is also indicated by a num-
ber of books and reviews that have appeared
on the topic, including books on EMA meth-
ods and findings by Stone et al. (2007b),
Hektner et al. (2007), and Fahrenberg &
Myrtek (2001); applications to mental health
by DeVries (1992); and discussions of data
analysis by Walls & Schafer (2006). Other
reviews include Wheeler & Reis (1991) on
sampling schemes for EMA methods, Scol-
lon et al. (2003) on the promise and chal-
lenges of EMA methods, Bolger et al. (2003)
on various uses of diary methods, and Pi-
asecki et al. (2007) on applications of EMA
methods to clinical treatment. A recent spe-
cial issue of the Journal of Personality (Tennen
et al. 2005) described several research pro-
grams applying EMA methods to issues rel-
evant to personality, clinical, and health psy-
chology, and several review papers discussed
their application to particular domains: Thiele
et al. (2002) reviewed the application of EMA
methods to clinical psychology, Moskowitz &
Young (2006) discussed applications to psy-
chopharmacology, and Beal & Weiss (2003) to
industrial psychology. The reader is referred
to these sources for more detail than can be
included here.
Finally, EMA methods are being used to
study a very wide range of behaviors, expe-
riences, and conditions. In a review of pub-
lished diary studies, Thiele and colleagues
(2002) found large groups of studies on pain,
mood, anxiety and anxiety disorders, eating,
sleep, gastrointestinal disorders, and alcohol
consumption. But even this is an incom-
plete list: EMA studies include studies of de-
pression, social support, initiate relationships,
diet, work activity and satisfaction, sexual
behavior, psychotherapy, drug use, allergies,
psychological stress, adverse effects of medi-
cations, self-esteem, and asthma, to name just
a few. Clinical disorders studied with EMA
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include addictive disorders, eating disorders,
anxiety disorders, depression, bipolar disor-
der, schizophrenia, sexual dysfunction, and
ADHD—in other words, the full range of
psychopathology. Beyond clinical syndromes
and symptoms, EMA is also widely used to
study basic adaptation processes relevant to
adjustment, such as coping, self-esteem, and
social support, as well as behaviors central to
health psychology and behavioral medicine,
such as coping with illness and treatment,
medication compliance, exercise, relaxation,
and safe sexual practices, among other behav-
iors. In sum, EMA methods are used in most
domains of concern to clinical psychology.
Historical Roots
EMA draws together several historical tradi-
tions, including diaries, self-monitoring, ex-
perience sampling, ambulatory monitoring,
and others. The oldest is the use of written
diaries for research (Verbrugge 1980), which
was systematically deployed in clinical re-
search in the 1940s. Self-monitoring of par-
ticular behaviors or experiences (Korotitsch
& Nelson-Gray 1999) has a long history in
research and particularly in behavioral treat-
ment. This includes simple counts of clinically
relevant events, but also collection of data
about their antecedents and contexts, which
provided data for “naturalistic functional anal-
ysis” (Schlundt et al. 1985). Related methods
included self-monitoring of particular targets;
a prominent example is the Rochester Inter-
action Record (Reis & Wheeler 1991), which
subjects used to record every social interac-
tion. Self-monitoring approaches often aimed
to capture all relevant events, and as a result
did not focus on sampling issues or collect data
outside of target events.
Other historical streams that fed into the
development of EMA focused on broad de-
scriptions of subjects’ behavior. One came
from the focus of the Kansas School of Eco-
logical Research (Barker 1978) on continuous
observation of behavior through the day in the
natural environment. Another derived from
the ethnographic method of describing indi-
viduals’ allocation of time, often to describe
differences among societies (Szalai 1966). A
variant of this within schools of manage-
ment and business examined the behavior of
workers in the workplace to understand how
they used their time and what activities they
engaged in.
More central to the development of mod-
ern EMA methods was the development
by Czikszentmihalyi and colleagues (DeVries
1992, Hektner et al. 2007) of the Experience
Sampling Method, demonstrating the inno-
vation of randomly sampling experience, ini-
tially using pagers to “beep” people at ran-
dom times to prompt them to complete diary
cards reporting their activity, mood, and/or
thoughts. The development of electronic di-
aries, based upon the emerging technology of
handheld computers, opened up new oppor-
tunities for more complex and sophisticated
EMA protocols that incorporated, combined,
and expanded upon the various approaches to
collecting EMA self-report data.
Enabled by technological developments,
ambulatory monitoring of cardiovascular
function, which became possible with the de-
velopment of wearable cardiac monitors, has
been used for several decades as a means of
understanding the link between experience
and cardiovascular health (Turner et al. 1994).
Ambulatory monitoring did not rely on self-
report (although it was often accompanied by
written diaries) and also enabled continuous
or near-continuous recording. Recent devel-
opments have expanded physiological moni-
toring to other parameters, such as galvanic
skin response, temperature, motion, and oth-
ers (Wilhelm et al. 2003). Often little atten-
tion was paid to sampling, in part because the
monitors could collect data almost continu-
ously (e.g., actigraph or heart-rate recording)
or at very high and stable frequencies. Some
physiological monitoring devices (e.g., mon-
itoring of blood-glucose, pulmonary func-
tion) require subjects to actively make pe-
riodic assessments, and thus raise many of
the sampling issues that arise with self-report.
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Technological developments have also en-
abled automated EMA assessment of behav-
iors (e.g., pill taking; Cramer et al. 1989) and
even of the physical environment (e.g., air
sampling; Saito et al. 2005).
These diverse traditions developed in dif-
ferent disciplinary contexts, often with dis-
tinct assessment targets. For example, the
Experience Sampling Method focused on sub-
jective states (Hektner et al. 2007 refer to it
as systematic phenomenology), whereas self-
monitoring focused on behaviors, and ambu-
latory monitoring focused on physiological
parameters. Moreover, because of their par-
ticular disciplinary histories and content foci,
these methods have been discussed in differ-
ent literatures, and investigators in one tradi-
tion often seem unaware of the others. Yet,
these methods share many goals, concerns,
and approaches. The object of EMA, which
attempts to encompass all of them, is to unify
these diverse approaches under a common
methodological framework.
AUTOBIOGRAPHICAL MEMORY
AND LIMITATIONS OF RECALL
A major motivation for EMA is to avoid the
pitfalls and limitations of reliance on autobio-
graphical memory. In this section, we expand
on the issues and concerns regarding autobi-
ographical memory, both to explain the ratio-
nale for EMA and to provide an essential foun-
dation to considerations of the uses of EMA
and specific EMA designs.
Research on autobiographical memory
(Bradburn et al. 1987) indicates that recall is
not just subject to random error but also is
fraught with systematic bias, which can dis-
tort recall even after relatively short inter-
vals. Modern cognitive science considers that
much of what we “recall” is actually recon-
struction, pieced together from fragmentary
inputs through the use of various heuristic
strategies. Many experiences are not retained
in memory, so often the information we are
asked to provide simply is not available for
direct retrieval. Experiences are particularly
likely to be encoded and retrieved if they are
emotionally salient or are unique; routine ex-
perience is less likely to be encoded and harder
to retrieve. Moreover, the process of retrieval
itself is subject to bias because the accessi-
bility of particular content in memory varies
with the subject’s mental state at the time of
retrieval.
Importantly, research inquiries usually ask
subjects not to just retrieve but also to aggre-
gate and summarize their experiences (e.g.,
“How intense was the pain, on average, to-
day?”). When trying to answer such questions,
subjects do not recall, enumerate, and then ag-
gregate their experience over time (Bradburn
et al. 1987). Rather, they use a variety of
heuristics to estimate the answer. The use of
cognitive heuristics and the processes of re-
trieval account for much of the bias in recall
data.
A key example of a biasing cognitive
heuristic is the “availability heuristic.” In its
original form, as described by Tversky &
Kahneman (1973), this refers to how peo-
ple make judgments about the frequency of
events. When deciding how often an event
(say, a fight with a spouse) occurs, a person
tries to retrieve an example. If an example is
easy to think of (i.e., it is easily “available” in
memory), the event is considered to be fre-
quent. One can see how this heuristic would
work much of the time—rare events should be
harder to “find” in memory. But one can also
see how biased it can be: if a fight was partic-
ularly memorable because it was intense, if it
is easily recalled because it was recent, or be-
cause one was recently reminded of it (say, by
a previous question in the assessment), then
the frequency of fights will be overestimated.
Importantly, the process of memory re-
trieval is itself subject to bias by the person’s
context and mental state at the time of re-
call. It has been shown, for example, that sub-
jects in a negative mood more easily recall
negative information than positive (Kihlstrom
et al. 2000). Similarly, subjects who are in pain
find it easy to remember past pain, but harder
to recall pain-free states; accordingly, it’s been
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Recall bias:
systematic errors in
data values (as
distinct from random
error) introduced by
processes of
autobiographical
memory
shown that subjects who are in pain at the time
of recall will overestimate their past pain (Eich
et al. 1985). This has profound implications
for research because it suggests that the sub-
ject’s state and situation at time of reporting
will influence what is reported.
A dramatic demonstration of the biases in
recall—and an indication of how quickly these
biases can set in—was reported by Redelmeier
et al. (2003). Summary ratings of pain by sub-
jects who had undergone a colonoscopy 20 to
30 minutes earlier were found to be unduly
influenced by the peak level of pain (presum-
ably because it was most salient) and the pain
intensity at the end of the procedure (most
recent). In other words, recall did not accu-
rately represent the average pain over the in-
terval, because it was based on a few of the
most memorable moments, essentially ignor-
ing most of the experience. This shows the
potential for bias even over short intervals.
Besides being distorted by the operation of
heuristic recall strategies, memory is also in-
fluenced by what we know and believe rather
than actually recall. People unconsciously re-
organize their “memories” to make them fit
a coherent script or theory of events or to
reconcile events with what transpired subse-
quently (Ross 1989). These biases are particu-
larly pernicious because they tend to produce
recalled patterns that are coherent and that
may conform to theoretical predictions, even
if they are false.
It is important to understand that these bi-
asing processes operate involuntarily and un-
consciously. They do not represent distortion
by uncooperative or defensive subjects—this
is simply the way memory operates. Research
inquiries often maximize the potential for bias
by asking about routine events, asking sub-
jects to summarize their experience, and so-
liciting recall in unusual settings (i.e., research
laboratories) and contexts (e.g., after being
asked other questions) that can bias recall.
Thus, heuristics that serve well enough to ad-
dress the demands placed on autobiographical
memory in everyday life can break down when
called upon to produce accurate research data.
THE USES OF ECOLOGICAL
MOMENTARY ASSESSMENT
EMA data are collected for a variety of pur-
poses (Bolger et al. 2003). We categorize these
into four classes: (a) characterizing individ-
ual differences, (b) describing natural history,
(c) assessing contextual associations, and (d )
documenting temporal sequences. We illus-
trate each with an example.
Individual Differences
When used to characterize individual differ-
ences, EMA data are aggregated to obtain a
measure of the subject that is collapsed across
time (i.e., across multiple EMA measures); for
example, the average intensity of pain experi-
enced by a pain patient. As an extension of
this, aggregated EMA data might be used to
quantify subjects’ characteristics at two dif-
ferent time points; e.g., pain before and after
treatment administration. As estimates of sub-
ject characteristics, aggregated EMA data are
expected to provide assessments of individuals
that are more reliable (because of aggregation)
and more valid (because of avoidance of recall
bias, representative sampling, and ecological
validity). Of course, if the variable is very sta-
ble over time, if recall bias were not present,
and if contextual factors did not influence the
variable, then there would be no advantage in
using EMA.
Natural History
To describe natural history, EMA measures
are analyzed for trends over time. In this case,
the within-subject variation over time itself is
the focus, and time is the independent vari-
able, the X-axis in a graphical representation
of the data. For example, McCarthy et al.
(2006) documented the trajectories of various
withdrawal symptoms that smokers experi-
enced after quitting. The EMA data demon-
strated that some symptoms peaked immedi-
ately when smokers quit and then decreased
over time, while others increased and per-
sisted, and still others increased only gradually
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over time. These patterns contradicted widely
held notions about the course of the with-
drawal syndrome and were associated with
differences in treatment outcome. Basic de-
scriptive information about the natural his-
tory of symptoms over time can often be an
important foundation for understanding clin-
ical disorders and outcomes.
Contextual Associations
Studies that examine contextual associations
look at the association or interaction between
two (or more) phenomena that co-occur in
time. Analyses of contextual associations are
often cross-sectional, even when data are col-
lected longitudinally, in that they examine
the co-occurrence of events or experiences,
not their sequence. In these analyses, time
is not explicitly represented—it is more of a
stage against which the events of interest play
out. For example, Myin-Germeys et al. (2001)
examined emotions accompanying stressful
events as a way to test a diathesis-stress model
of schizophrenia. They postulated that vul-
nerability to schizophrenia would be reflected
in excess emotional responses accompanying
stress. Schizophrenics, their first-degree rel-
atives (who are genetically vulnerable), and
normal controls were assessed 10 times daily
about stressful events and mood. An exam-
ination of individual differences in average
mood showed that the schizophrenics re-
ported more negative affect and more stress-
ful events, whereas vulnerable individuals and
normal controls did not differ. But a look at
stressor-mood associations revealed that the
first-degree relatives reacted more strongly
than did controls. Thus, examination of the
association between stressors and mood at
particular moments was key to understanding
what vulnerabilities might be conferred by a
genetic predisposition to schizophrenia.
Understanding the momentary cross-
sectional associations between different as-
pects of experience has also been important
for foundational studies of the structure of
behavior and experience; for example, data
on the covariation of momentary emotions
have been central in the debate about whether
positive and negative emotions are polar op-
posites or are independent dimensions and
can be experienced simultaneously. Feldman-
Barrett & Russell (1998) used EMA data to
address the argument that although one could
be both happy and distressed over some in-
terval of time, in a particular moment, one
could be either happy or distressed but not
both.
Although most designs examine associa-
tions between different variables within the
same person, an interesting variation consid-
ers how one person in a relationship affects the
other (Bolger & Laurenceau 2005). For exam-
ple, Larson & Richards (1994) asked members
of families to track their experience in parallel
and examined how the mood of each affected
the other. They found, for example, that a hus-
band’s mood when he comes home from work
significantly influences his wife’s mood, but
not vice versa.
Temporal Sequences
Finally, the longitudinal nature of EMA data is
used to explicitly examine temporal sequences
of events or experiences, to document an-
tecedents or consequences of events or be-
haviors, or to study cascades of events. In
these analyses, unlike those above, the order of
events or assessments is explicitly considered
and is a key focus. The previously cited study
of quitting smoking (Shiffman et al. 1997b) as-
sessed smokers’ affect and self-efficacy before
and after lapses to smoking, and their effects
on subsequent progression toward relapse, to
test Marlatt’s theory (Curry et al. 1987) that
the psychological response to lapses is what
drives progression toward relapse. Compar-
ing assessments obtained before the lapse and
afterward confirmed the theory’s hypothesis
that lapses would result in increased negative
affect and decreased self-efficacy (Shiffman
et al. 1997b). Continued EMA monitoring,
however, contradicted the theory’s prediction
that increases in negative affect and decreases
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in self-efficacy would predict the risk of
subsequent progression to another lapse or
relapse (Shiffman et al. 1996a). Importantly,
retrospective analyses had appeared to show
a relationship between initial responses to a
lapse and progression to relapse (Curry et al.
1987), but later comparisons with EMA data
(Shiffman et al. 1997c) showed that retrospec-
tive reports of lapse episodes were inaccurate
and biased: Subjects recalled their mood as
worse than it actually had been, and those who
had returned to smoking at the time of re-
call exaggerated how demoralizing the initial
lapse had been. Thus, prospective assessments
of the flow of behavior and experience, and of
the antecedents and consequences of events,
can enable a more valid and more detailed un-
derstanding of behavior.
These examples illustrate the use of EMA
data to evaluate hypotheses regarding the
dynamic interactions among processes over
time. Data provided by EMA studies may be
likened to a movie, in which dynamic rela-
tionships emerge over time, whereas global or
recall measures are analogous to a still pho-
tograph, a single static snapshot of time. By
providing temporal resolution, EMA meth-
ods allow investigators to examine sequences
of events and experiences and enable them to
describe and analyze cascades of events and
interactions between events that shape behav-
ior over periods of minutes, hours, or days.
Insight into microprocesses—the interplay or
cascade of cognitive, affective, and behavioral
variables over short intervals of time—is par-
ticularly important because many theories of
psychopathology and treatment focus on how
these processes unfold over time. Evaluation
of microprocesses also facilitates development
of interventions because an understanding of
how affect, cognition, and behavior interact
and unfold over time helps identify leverage
points for timely, and at least potentially more
efficacious, clinical interventions. The ability
to shed light on dynamic processes and situa-
tional influences is potentially the most criti-
cal contribution of EMA methods to clinical
psychology.
DATA COMPARING
RETROSPECTIVE AND
REAL-TIME REPORTS
Research suggests that recall measures, and
especially summary measures, are often biased
due to the use of mental heuristics to recall
information. This implies that there will be
discrepancies between EMA-based and recall-
based assessments of the same period. Rel-
atively few studies have examined such dis-
crepancies. In discussing this literature, we
distinguish comparison with aggregated EMA
measures from comparisons of disaggregated
time-specific estimates.
Comparison of Aggregated
Recall-Based Data and EMA
A number of studies have evaluated the rela-
tionship between EMA- and recall-based as-
sessments, comparing EMA assessments av-
eraged over some interval with recall-based
measures for the same interval. In some in-
stances, the two methods yield similar esti-
mates (Shrier et al. 2005), and in some other
cases, recall methods produce lower estimates
of intensity or frequency than do EMA meth-
ods (Carney et al. 1998, Litt et al. 2000). How-
ever, in many domains, recall-based assess-
ments tend to yield higher estimated levels
than diary ratings of the same target events:
That is, symptoms tend to be described as
more frequent, more intense, and longer last-
ing, sometimes dramatically so (Broderick
et al. 2006, Houtveen & Oei 2007, Shiffman
2007, Shiffman et al. 2006; see review in Van
den Brink et al. 2001). Behavior frequency is
also often overestimated in recall (Homma
et al. 2002, Shiffman & Paty 2003). This
phenomenon may be the result of the un-
due influence of more salient experiences in
recall: Intense pain is more salient than no
pain, headaches are more salient than non-
headaches, and so on, leading recall data to
overestimate clinical symptoms. An example
of this is the finding that subjects who had
the most intense headaches also overestimated
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headache frequency (Van den Brink et al.
2001).
Studies have also examined the correlation
between aggregated EMA and recall-based
data, which assesses whether the ranking of
individuals is similar across the two sources,
and can be high even when there are differ-
ences in the two means. Like the findings
on mean differences, the findings from cor-
relational studies are also variable. Studies of
drug use report good correspondence for fre-
quency or quantity used (Carney et al. 1998,
Shiffman & Paty 2003), but very poor cor-
respondence when characterizing situational
patterns of drug use, which involve more com-
plex judgments (Shiffman 1993, Todd et al.
2005). In one study of pain among chronic
pain patients ( J. Broderick, J. Schwartz, and
A.A. Stone, unpublished observations), corre-
lations in the 0.70s were seen between EMA
and recall-based measures of pain intensity,
whereas Van den Brink (2001) reported cor-
relations around 0.20 for headache frequency,
intensity, and duration.
Thus, findings on correspondence be-
tween aggregate EMA data and recall-based
estimates are inconsistent and variable. One
likely reason is that the magnitude and direc-
tion of recall bias can differ across subjects and
settings. Individual differences can affect re-
call accuracy. Feldman-Barrett (1997) found
that recalled distress was exaggerated among
more neurotic subjects and positive affect was
exaggerated among extraverted subjects, and
Van den Brink (2001) describes other individ-
ual differences that moderate recall bias. Be-
liefs can also moderate recall bias. McFarland
et al. (1989) found that women who believed
that their menstrual cycle influenced their
mood reported exaggerated negative mood in
retrospect, but only for menstrual days. In
contrast, women who did not believe men-
struation influenced mood did not show any
bias, either for menstrual or nonmenstrual
days.
Variation in the pattern of target symptoms
themselves can moderate bias. Stone et al.
(2005) showed that subjects whose pain was
relatively constant over time were able to es-
timate their pain more accurately since, in ef-
fect, they could easily know their typical pain
level or estimate accurately from any given
time point. In contrast, subjects whose pain
was variable demonstrated considerable bias.
Furthermore, Broderick et al. (2006) and oth-
ers have found that recalled pain was particu-
larly exaggerated when subjects were in pain at
the time of recall and understated when they
were not.
Thus, the validity of recall data likely varies
with characteristics of both the samples and
the setting. It is likely that the validity of re-
call is also influenced by the duration of the
recall interval and the variability, salience, and
uniqueness of what is being assessed: Some
kinds of end points may be well estimated,
whereas others are not. Better understand-
ing of these relationships could help estab-
lish when EMA is likely to add the most value
compared with aggregated recall measures.
Correlations Between Disaggregated
EMA and Recall
The studies reviewed above assess the cor-
relation between EMA- and recall-based es-
timates of experience when EMA data are
aggregated over time to broadly character-
ize person-level effects, and compared with
similar data based on global recall. How-
ever, EMA data are most often used not just
to characterize between-person differences,
but also to characterize within-person vari-
ations in experience over time, so that the
question is whether recall measures are able
to accurately reflect time-specific data. The
available evidence suggests that they cannot.
Even when global recall data correlate well
with aggregated EMA data, as in the stud-
ies cited above ( J. Broderick, J. Schwartz, and
A.A. Stone, unpublished observations; Carney
et al. 1998; Shiffman & Paty 2003), they
do not adequately capture time-varying data,
with correlations for recall of specific days
hovering in the range of 0.20–0.40. Moreover,
analyses show that the cross-day correlation
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also varies widely between subjects, with
some subjects actually showing negative cor-
relations between their recalled reports and
real-time reports of the same target events
(Carney et al. 1998, Searles et al. 2000).
In other words, even when recall appears
adequate to characterize aggregate experi-
ence, it is not typically adequate to charac-
terize day-to-day changes in cognitions and
behaviors of interest, which are typically the
focus of EMA research. This highlights one of
the unique contributions of EMA to the study
of processes that unfold over time.
Construct Validity of Real-Time
Versus Recall Assessments
In addition to comparisons of EMA-based and
aggregated recall-based assessments to each
other, comparisons can be made based on their
construct validity—in other words, their re-
lationships with other theoretically relevant
constructs. Several studies illustrate cases in
which EMA data show incremental validity
over and above retrospective or global as-
sessments of similar constructs. Kamarck and
colleagues (2007) directly contrasted the ef-
fect of job strain on cardiovascular outcomes
when strain was measured by EMA versus
global measures. Subjects filled out a stan-
dard global job strain questionnaire and used
an electronic diary to collect EMA data on
experienced strain every 45 minutes for six
days (data from the EMA was averaged to
create a single EMA summary variable). The
study’s outcome measure was a prospectively
assessed biological outcome: the progression
of blockage in the carotid artery (which corre-
lates with blockage of coronary arteries) over
the subsequent three years. EMA-based mea-
sures of job strain predicted progression of
arterial occlusion; however, traditional global
questionnaire measures of job strain did not.
Moreover, heart rate assessed by EMA in
the natural environment also independently
predicted progression of carotid blockage,
whereas heart rate measured in the lab did
not. This illustrates the potential of EMA
data to shed light on relationships that are
missed when relying on global retrospective
self-reports.
In a study of smoking, Shiffman and col-
leagues (2007) similarly compared global and
EMA-based measures, in this case, measures
of “negative-affect smoking”—the tendency
to smoke when distressed. The EMA-based
measure estimated negative-affect smoking
by comparing negative affect on smoking
and nonsmoking occasions; the global assess-
ment used standardized and validated ques-
tionnaires. Shiffman et al. tested the predic-
tion that smokers engaged in negative-affect
smoking would be more vulnerable to relapse
after they quit smoking. This was found to be
true for EMA-assessed negative-affect smok-
ing, but not for assessments based on standard
recall-based questionnaires.
The literature also suggests that EMA
measures may sometimes mirror the findings
of recall measures, but may capture the target
constructs with less noise and greater sensitiv-
ity. In a study of the efficacy of analgesics in
the treatment of rheumatoid arthritis, Nived
and colleagues (1994) reported that diary data
differentiated active treatment from control
after only four weeks of treatment, whereas it
took 24 weeks for the differences to become
apparent in recall measures collected at clinic
visits. In a related vein, analyses have shown
that real-time diary-based methods resulted
in decreased error variance when capturing
events (McKenzie et al. 2004) and scaled rat-
ings (Pearson 2004), making such data more
sensitive to treatment effects.
In contrast to these studies favoring EMA
data, J. Broderick, J. Schwartz, and A.A.
Stone (unpublished observations) recently
found that EMA and recall-based measures of
pain were equally correlated with medication-
taking and social impairment. Importantly,
other studies have illustrated cases in which
recall measures were actually better predic-
tors of subsequent behavior than were EMA
data. These cases are illuminating. In a study
of bias in recall of pain, Kahneman and col-
leagues (Redelmeier et al. 2003) showed that
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participants who were randomized to un-
dergo a longer colonoscopy, with more overall
pain, but who experienced less intense pain
near the end of the procedure actually re-
called lower overall pain. A follow-up revealed
that subjects who had undergone the longer
procedure—which was experienced as more
painful in real time—were more likely to re-
turn for a repeat colonoscopy. In other words,
their future behavior was related to the ret-
rospective summary of pain, not the momen-
tary experience. Similarly, Oishi & Sullivan
(2006) found that break-up of dating cou-
ples was better predicted from their retro-
spective summaries of relationship dissatis-
faction than from their daily ratings. These
findings make sense, because people shape
their subsequent behavior—whether to return
for a colonoscopy, whether to proceed with
a relationship—by reference to their stored
summary memory of the experience, not the
actual experience at the time.
These examples illustrate a key point: Even
if they do not match momentary experience,
retrospective impressions or global beliefs can
exercise greater control over subsequent be-
havior, since they represent the information
that people use to make subsequent decisions.
In this sense, the momentary and retrospec-
tive reports represent different perspectives
on the same event. If one is interested in what
was experienced in the moment (e.g., to un-
derstand the physiological effects of the pain
or to evaluate the effects of an analgesic) or
wishes to understand what are the proximal
determinants of a specific event, then the mo-
mentary data are likely to provide a more valid
picture. But if one is interested in the person’s
impressions of an event or in the prediction
of future behavior, then the retrospective im-
pressions may well be better predictors than
EMA. This suggests that researchers evalu-
ating the validity and utility of EMA and re-
call data must consider whether they are con-
cerned with understanding the experience as
lived or with understanding subjects’ impres-
sions of those experiences. As we have argued
with regard to assessments of psychological
Event-based
sampling: a method
of data collection
whereby a recording
is made each time a
predefined event
occurs
Time-based
sampling: a method
of data collection
whereby a recording
is solicited based on a
time schedule, often
based on random
time intervals
coping (Stone et al. 1998), confusion about
what is being assessed can misdirect theory
and research.
The discrepancy between momentary ex-
perience and global summary recall also sug-
gests that it would be worthwhile for research
to help us understand how momentary ex-
periences are integrated in the development
of global judgments. More research is also
needed on the circumstances in which global
or retrospective judgments are valid and cir-
cumstances in which EMA data are neces-
sary. In the interim, EMA is likely to provide
unique insights about processes that charac-
terize dynamics of behavior, cognition, and
affect over time.
ECOLOGICAL MOMENTARY
ASSESSMENT DESIGNS
AND APPROACHES
In this section, we describe and categorize
EMA designs, by which we mean the scheme
that dictates the scheduling, arrangement, and
temporal coverage of EMAs. In global assess-
ments such as personality questionnaires, the
researcher assumes that the assessment cap-
tures the subject’s entire experience in one fell
swoop, rendering it unimportant when the as-
sessment is made. In EMA, one assesses mo-
ments or periods of time, raising the issue of
how to ensure that the moments or periods
assessed are representative of the subject’s ex-
perience. In many cases, the assessments can
be conceptualized as a sample of the person’s
experience or behavior. Thus, designing an
EMA protocol can essentially amount to de-
signing a sampling scheme for moments in
an individual’s life. The most important influ-
ence on the design must be the aims of the
study.
EMA sampling and assessment schemes
can be roughly divided into event-based
sampling and time-based sampling schemes
(Shiffman 2007, Wheeler & Reis 1991).
Event-based schemes do not aim to charac-
terize subjects’ entire experience, but rather
to focus on particular discrete events or
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episodes in subjects’ lives—e.g., headaches
(Niere & Jerak 2004) or drinking episodes
(Todd et al. 2005)—and organize the data col-
lection around these events. Time-based sam-
pling typically aims to characterize experience
more broadly and inclusively—e.g., observing
how mood varies over time—without a prede-
fined focus on discrete events.
Event-Based Monitoring
In many disorders, the clinical and research
interest is in particular events or episodes, e.g.,
instances of drinking, violence, or panic at-
tacks. These cases lend themselves to event-
based monitoring, in which assessments are
triggered by the occurrence of a predefined
event of interest to the investigator. For ex-
ample, subjects might be asked to complete
an assessment when they have a panic at-
tack (Taylor et al. 1990), engage in a so-
cial interaction lasting more than 10 minutes
(Reis & Wheeler 1991), or take a medica-
tion ( Jonasson et al. 1999). Typically, the sub-
jects themselves determine when the event has
occurred and initiate an assessment (though
some events can be automatically detected
by devices; see Kop et al. 2001). Such pro-
tocols require clear definitions of the event,
which can be surprisingly thorny to delin-
eate: If subjects are to make a record every
time they eat, does chewing gum count as
eating? Sometimes, target events are defined
as episodic flare-ups of otherwise continu-
ous experiences, for example, a pain episode
in which pain is experienced more intensely
(McCarberg 2007), or an episode of intense
cigarette craving (Shiffman et al. 1997a).
Defining the algorithm for declaring an event
is particularly difficult—and important—in
these cases.
If one only needs a record of events, for ex-
ample, to ascertain their frequency and time
distribution, subjects need only note that an
event has occurred, e.g., press a button on
a recording device. More often, investiga-
tors wish to collect data about the event:
its duration, intensity, antecedent mood, etc.
(Schlundt et al. 1985, Shiffman et al. 1996b).
If the events are too frequent, it may not be
realistic to assess each event, in which case
a subset of them can be sampled at random
(Shiffman et al. 2002).
An important limitation in the use of
event-based monitoring is that there is often
no way to independently assess or verify com-
pliance; i.e., there is no way to know whether
events occurred that were not entered or (less
likely) entries made for events that did not oc-
cur. In a few studies, diary entries have been
compared to records made by separate elec-
tronic devices (e.g., instrumented medication
dispensers); these have suggested that medica-
tion compliance is exaggerated in self-report
(see Hufford 2007). Event entries can some-
times also be roughly confirmed by biochemi-
cal measures; e.g., Shiffman & Paty (2003) re-
ported that subjects’ electronic diary records
of cigarettes were consistent with biochemical
measures of smoking. In any case, event re-
ports are subject to error resulting from poor
compliance or falsification.
Time-Based Designs
Some clinical phenomena—e.g., mood,
pain—vary continuously and are not easily
conceptualized in an episodic framework.
In some instances (e.g., actigraphy, heart
rate, skin conductance), the phenomenon
can be monitored continuously. In the more
typical case, where this is not possible, EMA
protocols rely on time-based sampling. There
are many varieties of time-based sampling
schemes, which vary in schedule, frequency,
and timing (see Delespaul 1995 for more
detail).
The frequency of time-based assessments
will determine the resolution the study will
have. The resolution needed depends on the
goal of the study, what is known about the be-
havior studied, and the theoretical framework
of the study.
A variety of time-based assessment sched-
ules are used in EMA. Some administer assess-
ment at fixed intervals. This has been common
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in ambulatory monitoring of blood pressure
(e.g., every 30 to 45 minutes in Kamarck et al.
1998). Assessment at equal intervals allows
the time block to serve as the unit of analy-
sis and supports analyses that require evenly
spaced assessments, such as simple autocorre-
lation analysis and time series analysis. (Daily
diaries are a special case discussed below.)
Some studies have used somewhat irregu-
lar intervals, typically defined by social pa-
rameters: For example, Hensley et al. (2003)
had subjects complete an asthma diary in the
morning and evening of each day. Because the
time blocks are vaguely defined, they give sub-
jects considerable discretion in the timing of
assessments, and this has the potential to in-
troduce bias. For example, subjects might re-
member to complete their mood assessments
when they are reminded by extreme affect,
thus biasing the sample of mood.
An alternative to fixed intervals is a vari-
able schedule, which usually administers as-
sessments at random times in order to achieve
a representative sampling of subjects’ state. A
variation is stratified random sampling, from
within strata defined by blocks of time within
a day. For example, Affleck and colleagues
(1998) assessed subjects once in each pre-
defined time window in the morning, after-
noon, or evening, with assessments scheduled
at random within each interval. This guaran-
tees that the sample of assessments will evenly
sample time across the day and ensures (sub-
ject to missed assessments) that each time
block includes an assessment, which allows the
time block to serve as the unit of analysis.
Setting the frequency of assessments in-
cludes considerations of subject burden as well
as of how rapidly the target phenomenon is
expected to vary. Although assessing subjects
3 to 5 times per day is common, some studies
have succeeded with as many as 20 or more
assessments per day (Goldstein et al. 1992;
Kamarck et al. 1998, 2002, 2005, 2007). As-
sessment frequency may be varied to collect
more assessments at certain times of day if
those are of particular interest (Shiffman et al.
2000). Assessments should ideally be sched-
PDA: personal
digital assistant (a
handheld computer)
uled throughout the waking day. Some stud-
ies have limited assessment to a narrow range
of hours (e.g., 10am to 10pm in Kimhy et al.
2006), which misses early-morning and late-
night hours that may encompass important—
and substantially different—experiences and
behaviors.
When using time-based assessment sched-
ules, especially with variable intervals, EMA
studies require some method of signaling sub-
jects when an assessment is scheduled. This is
typically accomplished through the use of a
device—a beeper, phone, wristwatch, or per-
sonal digital assistant (PDA)—programmed
to signal the subjects at the appropriate times
(see Shiffman 2007 for a discussion of devices).
Thus, although events can be captured at
the subject’s initiative, continuous phenomena
typically have to be sampled using a suitable
time-based sampling scheme.
Combination Designs
Different sampling approaches can be fruit-
fully combined to test particular hypotheses.
When the researcher is interested in the cir-
cumstances that are associated with a target
event, it can be particularly helpful to com-
bine time- and event-based assessments in or-
der to provide a context for interpreting the
event data. Data on the situational context
of clinically meaningful events, such as panic
attacks (Margraf et al. 1987) or binge-eating
episodes (Engel et al. 2007) are hard to inter-
pret without comparison to base-rates (Paty
et al. 1992). For example, Greeno et al. (2000)
found depressed affect among bingers at the
time of a binge. However, this is difficult to
interpret: Does it mean that negative moods
help trigger binges, or just that binge eaters
are generally unhappy, even when not binge-
ing? By comparing affect reported during a
binge with affect reported on random occa-
sions outside of binges, Greeno et al. (2000)
were able to establish that binges were specif-
ically associated with more distress. This de-
sign is modeled after the case-control design,
with the events as “cases” and the nonevent
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data collected by time-based methods consti-
tuting the “controls,” and is often referred to
as a case-crossover design (Maclure & Mittle-
man 2000).
In EMA designs combining event- and
time-based assessments, time-based assess-
ments can also document the antecedents or
sequelae of events. For example, Shiffman &
Waters (2004) used time-based data to show
that ex-smokers were experiencing escalating
levels of affective distress in the hours preced-
ing a smoking lapse (the event) and to show
that self-efficacy decreased following a lapse,
but not after occasions when smokers success-
fully resisted a temptation to smoke (Shiffman
et al. 1997b). Time-based assessments can be
used to follow up on the sequelae of a recorded
event. For example, to test how quickly mi-
graine medications delivered pain relief and
how long the relief lasted, Sheftell and col-
leagues (2005) had subjects record the onset
of migraines and then scheduled a series of
assessments as follow-ups.
Combining different schedules of time-
based assessments can also be useful. For ex-
ample, Muraven et al. (2005) assessed social
drinking in subjects throughout the day but
also scheduled an assessment each morning to
ask about hangovers from the previous night’s
drinking. This illustrates how decisions about
design and scheduling of assessments need to
be driven by the research questions and by
knowledge about the natural history of the
target behavior.
Use of Recall in EMA
Although some EMA studies truly focus on
the moment, many assessments involve some
degree of retrospection. For example, Affleck
and colleagues (1998) asked fibromyalgia sub-
jects to report on their pain and fatigue over
the past 30 minutes. Event-based diaries of-
ten involve some retrospection if the entry
is made after the event: For example, studies
with the Rochester Interaction Diary (Reis &
Wheeler 1991) ask subjects about social in-
teractions they had just concluded. Thus, the
focus on momentary experience is not abso-
lute; it might more liberally be thought of as
a focus on recent experience. Of course, some
events and experiences are likely to be recalled
more accurately, particularly if they are un-
common and/or highly salient (e.g., a major
marital spat) or recent. However, since the lit-
erature shows that recall can be biased over
even a short interval, the researcher needs
to carefully consider the use of recall meth-
ods and the potential for bias even over short
intervals.
Sampling Versus Coverage Strategies
When subjects are assessed intermittently and
the focus is on their momentary state, the as-
sessments do not provide complete coverage
of their daily experience. That is, even though
we may have assessed their mood 12 times in a
day, and found them happy each time, it is pos-
sible that they experienced moments of mis-
ery in between the assessments. A sampling
strategy recognizes that only some moments
are assessed, but relies on the idea that, over
multiple days and multiple assessments, both
moments of happiness and moments of misery
will be sampled, and the mix will be represen-
tative of the subjects’ average mood.
In lieu of a sampling strategy, investiga-
tors sometimes adopt a coverage strategy,
which aims to cover every moment of the day.
For some kinds of objective data, continu-
ous measurement (e.g., actigraphy) is possi-
ble, enabling true coverage (e.g., Tulen et al.
2001). For self-report measures, continuous
assessment is not possible, so investigators
try to obtain coverage by having subjects re-
call and summarize the period between as-
sessments. This is sometimes implemented by
asking subjects several times a day to recall
and summarize their experience since the last
assessment, providing piecemeal coverage of
the entire day. For example, Van den Brink
et al. (2001) assessed pediatric headache pa-
tients four times each day, and at each as-
sessment, asked them to recall and character-
ize headaches experienced since the previous
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assessment. Besides being vulnerable to biases
introduced by recall, this strategy requires
subjects to accurately maintain a timeline of
experience and focus on experience since the
last assessment. Research suggests that peo-
ple are particularly poor at keeping track of
time and identifying when events took place
(Sudman & Bradburn 1973), suggesting that
this approach needs to be treated with cau-
tion. Coverage strategies may be useful when
the investigator needs an absolute estimate or
count of events; otherwise, sampling strate-
gies can yield representative estimates.
Daily Diaries: A Special Case of EMA
Daily (i.e., once-a-day) diaries are particularly
popular with researchers and clinicians be-
cause of their ease of administration and rela-
tively low subject burden. Within the frame-
work that we have been discussing, daily
diaries are fixed-interval assessments with an
assessment frequency of once per day, em-
ploying a retrospective coverage strategy.
Even though daily diaries rely on recall of the
entire day and therefore are not momentary,
we consider them as falling into the family of
EMA designs because they are administered
repeatedly and provide a dynamic look at the
variables investigated, although with less res-
olution than that of within-day assessments.
Daily diaries bring some of the benefits of
EMA in terms of illuminating process over
time, but they also carry with them some of the
limitations of retrospective assessments, ask-
ing participants to summarize the entire day’s
experience. This may introduce some bias be-
cause moods can vary substantially from one
moment to the next, and true recall is likely
to stretch the capabilities of autobiographi-
cal memory. Moreover, research on autobi-
ographical memory suggests that biases due
to heuristic recall strategies operate even over
short time frames. The typical scheduling of
diary completion at the end of the day may
itself become a source of bias, since this tends
to be a highly unrepresentative moment, when
subjects may be particularly fatigued, for ex-
ample, which could bias their recall of the day’s
experience. Accurate recall may be more likely
when subjects are asked to recall less frequent,
more notable and salient events, such as the
occurrence of a migraine headache. Compar-
isons of daily diary data to real-time data will
enable researchers to determine whether the
former is a reasonable proxy for the latter. Re-
search is needed to shed light on when ac-
curate recall is and is not likely. Thus, daily
diaries require a cautious approach.
Besides concern about retrospective bias,
daily assessment also provides limited tempo-
ral resolution in which to observe behavior;
that is, within-day processes may be critically
important for some phenomena. This was il-
lustrated in a study by Shiffman & Waters
(2004) on the antecedents of smoking lapses.
Daily diary data showed no increase in nega-
tive affect in the days leading up to a lapse and
no association between daily negative affect
and lapse risk. However, examination of hour-
by-hour affect data revealed a steep increase
in negative affect in the hours immediately
preceding lapse episodes. Thus, day-level data
may miss important sources of dynamic varia-
tion that drive behavior. However, when used
carefully, especially for highly memorable and
slow-moving targets, daily diaries can never-
theless be a tremendous asset for studying cer-
tain questions and are often an improvement
over relying on global retrospective recall.
USE OF ECOLOGICAL
MOMENTARY ASSESSMENT
IN TREATMENT
For Assessment
Although we have been addressing the use of
EMA for research data, it also seems natural
to use EMA for ongoing assessment during
treatment. The treatment context includes
many features that lend themselves to EMA
methods: The client is likely motivated to
devote energy to assessment, and there are
usually clear target behaviors or experiences
on which to focus, dictated by the client’s
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presenting problem, the nature of the pathol-
ogy, and/or the clinical formulation of the
case. EMA methods lend themselves to idio-
graphic n = 1 analysis; even formal statistical
testing can be done by using a single client’s
data to guide therapy and assess progress (e.g.,
Delespaul 1995). Properly structured EMA
data lend themselves to the sort of micro-
analysis of process that is often the subject of
therapeutic discussion, and that is seen as re-
vealing opportunities for intervention (“Let’s
figure out what led up to your anxiety attack
so we can understand it and think about how
to prevent it”). Because change is expected
during treatment, ongoing assessment can be
informative. EMA could also prove useful in
shedding light on processes and mediators of
psychotherapy-induced change.
EMA assessments are only beginning to
see application in clinical settings. Norton and
colleagues (2003) conducted a small outcome
study of CBT for binge eating, in which pa-
tients were randomized to use EMA-based
assessment or not. There were no signifi-
cant differences in the primary outcome, but
there were strong trends favoring the pa-
tients with EMA, suggesting that a larger
study would have demonstrated reliable dif-
ferences. Protocols to make optimal use of
EMA in treatment have yet to be developed.
Widespread use of EMA in treatment will
also have to overcome both real and perceived
barriers of the technical and financial bur-
den of these methods. We expect that EMA
methods will see increasing use in clinical set-
tings over the next decade (see Piasecki et al.
2007 for a review of EMA applied to clinical
assessment).
For Intervention
Although using EMA for clinical assessment
would be a minor extension of its use in
research, applying EMA methods directly
to intervention—that is, implementing real-
time in-the-moment interventions as sub-
jects go about their daily lives—may open
up more radical developments. Bridging the
gap between patients’ here-and-now experi-
ences and behaviors in the real world and the
removed, confined, and limited contact with
the clinician in the consulting room has al-
ways been a major challenge for psychological
treatment. Only a few papers have described
momentary interventions, and fewer still have
evaluated them.
Newman et al. (2003) reviewed a vari-
ety of palm-top-assisted treatments for psy-
chological disorders. Newman et al. (1997)
reported that a brief palm-top-assisted mo-
mentary intervention for panic disorder was
equivalent in efficacy to a longer therapist-
administered treatment. The control group
in this study also engaged in EMA and
may have benefited from that, which high-
lights the importance of identifying the
incremental benefits of EMA intervention
versus EMA. Momentary interventions have
also been described for eating disorders
(Norton et al. 2003) and addictive disorders
(Riley et al. 2002). Carter et al. (2007) describe
a particularly sophisticated and interactive
EMA-based treatment program for smoking
(still under evaluation) and present a concep-
tual foundation of EMA-based treatments.
At this stage, then, EMA-based momen-
tary intervention remains a promising, but
only partly proven, idea. However, its poten-
tial seems enormous. The idea of momentary
treatment, delivering intervention immedi-
ately on-the-spot and as needed in real-world
settings—a “therapist in your pocket”—holds
promise for addressing behavior at crucial
moments in the patient’s life. EMA-based
treatment can provide behavioral guidance or
other interventions (e.g., relaxation stimuli)
throughout a patient’s day as well as just at the
moment they are needed. By learning from
an individual’s history, algorithms could, for
example, tailor coping suggestions based on
what has worked before for this patient in this
situation. Furthermore, by observing the pa-
tient over time, predictive algorithms could
anticipate and respond to challenges before
they gain strength, for example, noting rising
stress levels and intervening (or contacting a
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counselor) before they result in maladaptive
behavior. In-the-moment interventions have
only begun to be explored, but they have the
potential to revolutionize clinical treatment.
MEASUREMENT
CONSIDERATIONS FOR
ECOLOGICAL MOMENTARY
ASSESSMENT SELF-REPORTS
When self-report assessments are used in
EMA, some special considerations are needed.
Many questionnaires were not designed for
assessing momentary states; the instructions
may have a longer recall time frame or no
time frame at all. Whether adapting an ex-
isting instrument for EMA or creating a new
one, it is important to consider whether the
item makes sense in the new time frame—i.e.,
momentary, hourly, etc.—both from the in-
vestigator’s conceptual perspective and from
the subject’s perspective. For the latter, cog-
nitive testing of proposed assessments (Willis
2005), as well as pilot testing of assessments
in the field, is usually prudent.
An unusual aspect of EMA studies is that
subjects will typically encounter each assess-
ment many, many times. This requires that
assessments be well tuned: Something that is
just a small annoyance when seen once can
become a real irritant when encountered five
times a day for weeks.
Construction of EMA assessments may
also be influenced by the device or medium
used. For example, PDAs have limited screen
display space, requiring that items and re-
sponse options be reasonably succinct. When
interactive voice response systems are used,
the length, complexity, and number of op-
tions needs to be severely limited, keeping in
mind that subjects must listen to and remem-
ber all the response options and their corre-
sponding keypad numbers. Simply moving a
questionnaire from paper to a screen-based
electronic device should not be problematic:
A meta-analysis showed that paper-based and
screen-based questionnaires were equivalent
(Gwaltney et al. 2007).
Use of programmable electronic devices
to administer assessments provides oppor-
tunities to change the order in which as-
sessment items are administered. This can
be used to present items in random order
to counterbalance any effects of item se-
quencing (for free access to such software,
see http://www.experiencesampling.org/).
This programmability could be used to im-
plement computer-adaptive testing (Chang &
Reeve 2005), which provides efficient assess-
ment of a construct with a minimum num-
ber of items, by dynamically changing which
items are administered to particular subjects
based on their responses to prior items.
Although most EMA studies collect struc-
tured quantitative data (using structured
scales to quantify responses), EMA meth-
ods can also be used to gather qualitative
data. Diaries can allow write-in responses, and
O’Connell et al. (2002) have supplemented
PDAs for quantitative assessment with tape
recorders for collecting qualitative narratives
for later coding. Automatically activated tape
recorders have also been used to collect qual-
itative data (i.e., conversations) without the
need for subject intervention (Mehl et al.
2001). Assessments of physiological parame-
ters usually bring with them a set of techni-
cal concerns specific to the system being mea-
sured and the method used.
Besides keeping in mind the special mea-
surement issues that apply to EMA, it is
equally important to recognize that many of
the measurement issues that apply to global
psychometric assessment also apply to EMA.
That is, it is important that assessments be re-
liable and valid; in EMA, reliability can some-
times be achieved through aggregation across
multiple assessments rather than across mul-
tiple items within a single assessment. The
meaning of EMA assessments has to be care-
fully considered; Schwarz (2007) has spec-
ulated that focusing self-report on immedi-
ate experience might shift the individual’s
focus to very small events at the cost of the
“big picture.” It is also important to keep
in mind that self-report data collected via
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EMA methods are still self-report data and
are subject to many of the limitations inher-
ent to self-report. Like any self-report data,
EMA data can be adversely influenced by the
effects of subjects’ psychopathology (Kessler
et al. 2000) and by deception or self-
deception.
METHODOLOGICAL
CONSIDERATIONS IN
ECOLOGICAL MOMENTARY
ASSESSMENT STUDIES
Reactivity
Reactivity is defined as the potential for be-
havior or experience to be affected by the
act of assessing it. Behavioral studies of self-
monitoring, in which patients were asked to
monitor the behavior they were trying to
change, often demonstrated reduction in the
problem behavior due to monitoring alone—
so much so that self-monitoring came to be
considered a part of behavior-change treat-
ment, not just assessment. However, reactivity
is not universally observed. In particular, stud-
ies showed that reactivity emerged when sub-
jects were trying to change the target behavior
and when the behavior was recorded prior to
being executed (e.g., recording a meal before
eating it)—in other words, under conditions
that provide both the motivation and the op-
portunity to exert control over the behavior
(Korotitsch & Nelson-Gray 1999). This sug-
gests that EMA researchers need to be con-
cerned about reactivity under such conditions,
although there has not yet been a direct test
of this idea.
When such conditions are not present,
several studies of EMA find little or no
evidence of reactive effects (Cruise et al.
1996; Hufford & Shields 2002; Hufford et al.
2002a,b; Hufford & Shiffman 2002; Litt
et al. 1998; Stone et al. 1998). In the most
controlled study of reactivity to EMA, Stone
and colleagues (2003a) assigned subjects with
pain syndromes to complete either no EMA
monitoring or sampling of their pain using
electronic diaries 3, 6, or 12 times daily. No
evidence was found that the pain ratings
were systematically reactive to the EMA
monitoring.
Besides traditional reactivity, one might
also be concerned that the burden of moni-
toring, including being interrupted by “beep-
ing” throughout the day, might cause distress
that would bias the data. Again, the evidence
suggests this is not typical. The Stone et al.
(2003a) study found no trend over time in pain
ratings and no systematic effect on pain rat-
ings of increased prompting, despite a delib-
erately aggressive prompting and assessment
schedule.
Given the earlier literature suggesting
that reactivity can occur, the literature does
not completely resolve when reactive effects
might or might not be observed. EMA re-
searchers should be alert to the potential for
reactivity while recognizing that little evi-
dence has been found to support the concern
that EMA engenders significant reactivity.
Compliance
While EMA methods promise to capture
data closer in time to events and symptoms
of interest, they also place on subjects the
burden of making timely recordings as they
go about their daily lives. Missing assessments
have the potential to bias the obtained sample
of behavior and experience, especially if the
missing data are nonrandom. As a result,
EMA studies place a premium on obtaining
high levels of subject compliance with the
assessment protocol.
The methods used to collect diary data can
affect the investigator’s ability to obtain and
document compliance. Studies using paper di-
aries often report that about 90% of diary
cards are returned (Hufford & Shields 2002).
However, timely compliance is often inferred
from the date and time subjects have recorded
on the diary card. This opens the door for sub-
jects to hoard and backfill diaries (that is, to
complete entries, perhaps en masse, after the
fact) while seeming compliant.
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Concern about hoarding and backfilling
is heightened by the findings from studies
in which subjects completed written diaries
while also using electronically instrumented
devices (e.g., inhalers, blood glucose moni-
tors) that independently tracked the actual
time and date of events, such as medica-
tion taking or glucose monitoring. Across
eight studies (Hufford 2007), objective data
from the devices indicated that compliance
had actually been much lower than was in-
dicated by the written diaries: Many of the
written entries had been falsified. Moreover,
the written entries were systematically biased,
for example, showing better glycemic con-
trol than had actually been achieved (Mazze
et al. 1984). The written diary records un-
derstated problems of glucose control and ac-
centuated the concern about backfilling and
faked compliance. These concerns were fur-
ther accentuated by reports from paper di-
ary studies in which high proportions of sub-
jects later admitted to backfilling entries, even
when they had been electronically prompted
at the appropriate times and had recorded
those times on their diary cards (Litt et al.
1998, Moghaddam & Ferguson 2007).
To assess true compliance with written di-
aries, Stone et al. (2002) used an instrumented
paper diary (IPD), which was covertly instru-
mented with photosensors that recorded the
opening of the diary booklet—a prerequisite
to completing diary cards. Chronic pain sub-
jects were assigned to use either the IPD or
a PDA-based electronic diary to record their
pain at three scheduled times daily for three
weeks. Subjects were trained on the diary,
and steps were taken to encourage motivation
and compliance. The IPD allowed compar-
ison of reported compliance—based on the
time and date handwritten on returned diary
cards—and actual compliance—based on the
electronic records. Reported compliance was
90%, as in many other paper diary studies.
However, actual compliance was estimated at
11%. In other words, almost 90% of the sub-
mitted diary cards had been falsified. Evidence
indicated that the diaries had been hoarded
for days and backfilled. More disturbing still,
many subjects also showed evidence of fill-
ing their paper diary cards in advance of the
stated time (Stone et al. 2003b), which ob-
viously renders the data invalid. Broderick
et al. (2003) subsequently showed that adding
an audible reminder to complete the diary
boosted compliance only modestly.
The other 40 pain sufferers in the study
by Stone et al. (Stone et al. 2002, 2003a,b;
Stone & Shiffman 2002) had been given an
electronic diary, which prompted for assess-
ments and did not allow entries outside the
designated time windows. These subjects ac-
tually did complete 94% of their assigned as-
sessments on time.
These compliance findings by Stone and
colleagues have stirred debate among diary
researchers (Green et al. 2006, Tennen et al.
2006), with critics noting, for example, that
various procedures (e.g., having subjects re-
turn diaries daily by mail, so that postmarks
provide some degree of time-stamping) might
improve timely compliance with written di-
aries. In any case, the Stone et al. study (Stone
et al. 2002, 2003a,b; Stone & Shiffman 1994,
2002), along with the prior literature docu-
menting falsified paper diary entries (Hufford
2007), raises critical questions about timely
compliance. Paper-and-pencil diaries are vul-
nerable to being falsified, and both forward-
and backfilling are possible and potentially
frequent, making verification of timely com-
pliance both essential and challenging. Thus,
the burden of proof falls to the EMA inves-
tigator to establish, by whatever means, the
timeliness of recording.
The most common way to ensure and doc-
ument timely compliance is the use of elec-
tronic diaries, which tag each record with time
of entry and thus allow for detailed analy-
sis of compliance, particularly with interval-
or signal-contingent recordings. Many elec-
tronic diary studies document compliance
rates around 90% (Hufford & Shields 2002).
However, good compliance is not univer-
sal even with electronic diaries; rates as low
as 50% have been reported (e.g., Jamison
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et al. 2001), suggesting that the mere use
of electronic diary technology is not, by it-
self, a panacea. A variety of suggestions of
ways to enhance compliance with electronic
diary studies has been presented elsewhere
(Hufford & Shiffman 2003). As noted above,
compliance with event-oriented protocols is
difficult to verify.
SPECIAL POPULATIONS
Because of the burdens they place on subjects,
EMA methods often raise concerns about ap-
plication to special populations. These con-
cerns are often magnified when EMA stud-
ies employ electronic devices, such as PDAs
or cell phones, for data collection. A com-
mon concern is that elderly subjects will
be unable or unwilling to operate high-tech
devices. However, data on subject prefer-
ence for electronic versus more traditional
paper diaries do not support this assump-
tion. In a meta-analysis of patient prefer-
ence, older subjects are actually less likely
to prefer paper diaries (in Shiffman et al.
2007). Similarly, although there have been
concerns about the use of such technology
in low-education, low-socioeconomic-status
subjects, Finkelstein et al. (2000) demon-
strated good success with just such a sample.
Different concerns are sometimes raised
about the use of diaries with children. Sev-
eral studies have demonstrated that children
are able to use electronic diaries, and good
compliance and results have been seen with
children as young as 7 (see Van den Brink
et al. 2001). Of course, the use of EMA meth-
ods does not obviate, and may increase, some
more general issues about assessment of chil-
dren, such as comprehension of the question-
naires used.
Concerns also arise about whether some
clinical populations might be unable to per-
form in EMA studies precisely because of their
psychopathology. In this regard, it is notable
that several studies have been successfully
carried out among schizophrenics (Delespaul
1995, Myin-Germeys et al. 2001), and good
compliance using cell phones for EMA re-
porting has been reported in a sample of
homeless crack addicts (Freedman et al. 2006).
These examples suggest that, with appropriate
sensitivity, EMA methods and related tech-
nology may be useful in a wide array of patient
populations and that investigators should not
make decisions about feasibility without test-
ing their assumptions.
A subtler concern that is not addressed
by the performance of special populations
in EMA studies is that subjects who volun-
teer for and complete demanding EMA stud-
ies may not be representative. There have
been no reports of particular recruitment dif-
ficulties or notable deviations in EMA study
samples, but this has not been systematically
evaluated. It seems likely that personal and
environmental factors may discourage some
subjects’ participation in EMA studies. Oc-
cupational demands may preclude availabil-
ity for momentary assessment (consider sur-
geons and assembly line workers, although see
Goldstein et al. 1992). Also, some work en-
vironments may be so noisy as to preclude
hearing prompts or using a phone. Motor im-
pairments, impaired vision or hearing, and il-
literacy may preclude participation in EMA
(and in many non-EMA) studies. Finally, sub-
jects who are unfamiliar with or fearful of
technology may be put off by EMA studies
using high-tech devices. The limits of EMA
and their impact on studies should be contin-
ually evaluated.
ANALYSIS OF EMA DATA
EMA data usually consist of a large number of
observations from each subject, with the num-
ber and timing of observations often vary-
ing between subjects. EMA data do not lend
themselves to the basic approaches most clin-
ical psychologists learned in graduate-school
statistics classes, which require independent
observations. Nor do they fit easily into tradi-
tional repeated-measures designs, which typi-
cally require the same number of observations
for each person and no missing data. However,
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a variety of methods—essentially extensions
of the regression framework most psycholo-
gists are familiar with—can handle such data.
Known variously as random effects models,
multilevel or hierarchical analysis, and gen-
eralized estimating equations, these methods
implement regression models while account-
ing for the interrelationships of observations
within subjects. Extensions of these methods
go beyond linear regression to cover logistic
regression and survival models, among oth-
ers. Detailed exposition about these methods
is beyond the scope of this review; the reader
is referred to Schwartz & Stone (1998, 2007)
for detailed and practical guidance on appli-
cations of these models to EMA data. The
bottom line is that EMA researchers can use
easily available software to apply the concep-
tual models they are familiar with from more
traditional between-subjects analyses to EMA
data. Besides these relatively familiar statisti-
cal models, a variety of novel approaches can
fruitfully be applied to EMA data (Walls &
Schafer 2006).
PRACTICAL ISSUES IN
ECOLOGICAL MOMENTARY
ASSESSMENT
The implementation of EMA places unique
demands on both researchers and subjects. A
detailed discussion of the practical aspects of
implementing EMA is beyond the scope of
this review. The interested reader is referred
to Hufford (2007). Here we touch only briefly
on considerations of hardware and software,
and management of subjects and data.
EMA Hardware and Software
An investigator planning an EMA study faces
many practical issues and decisions. One key
decision is what type of mechanism to use to
capture data. Although EMA is most closely
associated with the use of palm-top comput-
ers (Hufford & Shields 2002), the method is
hardware agnostic and encompasses a range
of high- and low-tech devices, ranging from
paper and pencil to futuristic wireless sen-
sors (Intille 2007). The key factor to con-
sider in selecting a hardware platform is the
support provided for key functions, including
the ability to prompt subjects to complete as-
sessments, manage prompting schedules (in-
cluding randomization and contingencies),
present assessment content to subjects, man-
age assessment logic such as branching, ac-
cept and store subjects’ self-report data, time-
stamp entries to avoid faked compliance,
and/or directly collect physical or physio-
logical data (see Shiffman 2007). Investiga-
tors should also consider the suitability of a
particular device or medium to their subject
population: For example, a small screen or a
telephone system may be less suitable for an
elderly population with visual or hearing im-
pairments, respectively.
The cost of devices and of software devel-
opment is often an additional consideration.
Investigators should avoid being overly influ-
enced by initial start-up costs and also should
consider downstream costs, such as the cost
of cell phone service or of data entry from pa-
per diaries. Unfortunately, high fixed costs of
technological solutions can make it very hard
to initiate small studies or pilot studies.
EMA approaches using electronic devices
require software for basic system functional-
ity and for the specifics of the study proto-
col. The success of such studies depends on
correct and robust performance of software,
which can often be complex. Both freeware
and commercial versions of EMA software are
now readily available. Le et al. (2006) have re-
viewed a number of freely available programs,
and a number of commercial vendors also pro-
vide programming and support services for
EMA studies. These base systems have to be
configured or customized to the needs of a
particular study. Researchers should carefully
consider capabilities and limitations of various
software systems. For example, some systems
can only accommodate signaling during speci-
fied periods of the day, which can bias the sam-
ple by, for example, omitting early-morning
and late-night events, which may be highly
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salient. Some programs may support event- or
signal-driven assessments, but not the combi-
nation of the two. In light of the availability
of software from multiple sources, investiga-
tors are well advised to use existing software or
services.
Other Practical Considerations
Investigators should also consider procedures
and resources related to managing study
subjects. Training of subjects on the protocol,
the assessment, and any device used is an es-
sential aspect of EMA studies. Data manage-
ment is an additional consideration in EMA
studies. EMA studies can produce volumi-
nous datasets with hundreds of thousands of
observations, possibly of diverse kinds (e.g.,
momentary, daily, events). Additional compli-
cations include the fact that the records are
ordered in time and the temporal relation-
ships need to be maintained, and there may be
nondata records that do not represent subject
assessments (e.g., records of missed assess-
ment prompts) that also have to be maintained
within the database. Data management facili-
ties for maintaining these databases and pro-
ducing analytical datasets are an essential re-
source for EMA studies and should be planned
into the study.
CONCLUSION
EMA studies help us appreciate the impor-
tance of change and context in everyday be-
havior and experience. The dynamic influence
of context is demonstrated not only for con-
structs that we might expect to be variable,
such as affect, craving, and pain, but also for
many constructs that are typically conceptu-
alized as stable trait-like characteristics, such
as extraversion (Fleeson 2001), self-esteem
(Kernis 2005), coping style (Schwartz et al.
1999), and self-efficacy (Gwaltney et al. 2005).
EMA’s microscopic focus and temporal res-
olution is beginning to help us see the un-
derlying dynamics behind even trait-like con-
structs. EMA studies suggest that behavior
and experience are much more dynamic, and
much more influenced by its immediate con-
text, than we usually envision. Even individual
differences can sometimes be best understood
through analysis of within-person variation.
For example, differences in how persons react
to situational stimuli, such as stressors, are re-
lated to personality (Feldman-Barrett 1997),
psychopathology (Myin-Germeys et al. 2001),
and clinical outcomes (Kamarck et al. 2007),
and within-person variation in response may
sometimes be as important as the mean level
(Gwaltney et al. 2005, Kernis 2005). Despite
their limitations, EMA methods promise to
enhance our understanding of the dynamic
interactions between individuals and their
environments.
Clinical psychology—and psychology in
general—is prone to overestimate the role of
stable traits in determining behavior and to
underestimate the influence of the local set-
ting on behavior (Mischel 2004). Our behav-
ior in daily life is influenced not just by our
predispositions, but also by where we are and
whom we are with, by how we are feeling and
what situation we are in, by what has recently
happened and what we have done or felt in
the minutes and hours preceding the present
moment. One context can elicit dysfunctional
behavior while another elicits a healthier re-
sponse; one can fuel psychopathology or set
us on a course toward improvement. Under-
standing life as it is lived, up close, will help
us better understand both health and pathol-
ogy and help us see where there are oppor-
tunities to intervene on the side of health.
This requires methods that examine behav-
ior at the appropriate level of granularity:
“Research methods that examine this land-
scape from 10,000 feet cannot shed light on
how this landscape is shaped at ground level”
(Shiffman 2005, p. 1743). EMA methods pro-
vide an important tool to help clinical psy-
chology explore the dynamic nature of behav-
ior, thought, and feeling as they unfold over
time.
24 Shiffman
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Stone
·
Hufford
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SUMMARY POINTS
1. Autobiographical memory processes can introduce bias into retrospective self-reports,
which form the bulk of clinical assessments.
2. EMA is a collection of methods for obtaining repeated real-time assessments of sub-
jects’ behavior and experience in their natural environments, to minimize recall bias,
maximize ecological validity, and document variation over time.
3. EMA encompasses a variety of diary approaches and technologies used to collect data
on a schedule (e.g., daily diaries or assessments scheduled at random) or in response
to clinical events (e.g., symptom episodes or behaviors).
4. The collection of frequent assessments makes EMA studies well suited to study
microprocesses—i.e., how behavior and experience vary over time and across
changing contexts.
5. Although sometimes retrospective self-reports correspond well with those based on
aggregated EMA data, recall of behavior and experience over time does not correspond
well to real-time EMA assessments.
6. The application of EMA methods for assessment and intervention in treatment is
promising but is in its infancy.
7. EMA methods have great potential to advance the science and practice of clinical
psychology by providing more valid and more detailed data about real-world behavior
and experience.
FUTURE ISSUES
1. Further prospective longitudinal analyses of EMA data are necessary to shed light on
theoretically relevant microprocesses in studies of psychopathology and treatment.
2. Further improvements in technological tools for EMA studies would enhance ease of
use, reduce cost, and expand capabilities.
3. An improved understanding is needed of the relationship between recall and real-time
EMA data, the circumstances under which recall may be accurate, and the processes
by which persons develop retrospective accounts of their experience.
4. Models are needed for application of EMA methods to clinical assessment and
intervention.
ACKNOWLEDGMENTS
The authors are grateful to Julie Mickens for invaluable help in preparing this manuscript.
DISCLOSURE STATEMENT
S. Shiffman is a founder and Chief Science Officer of invivodate, Inc., which provides electronic
diary software and services for research. A.A. Stone and M.R. Hufford own stock in invivodata,
Inc.
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Ecological Momentary Assessment 25
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Annual Review of
Clinical Psychology
Volume 4, 2008
Contents
Ecological Momentary Assessment
Saul Shiffman, Arthur A. Stone, and Michael R. Hufford ppppppppppppppppppppppppppppppp1
Modern Approaches to Conceptualizing and Measuring Human
Life Stress
Scott M. Monroe ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp 33
Pharmacotherapy of Mood Disorders
Michael E. Thase and Timothey Denko pppppppppppppppppppppppppppppppppppppppppppppppppp 53
The Empirical Status of Psychodynamic Therapies
Mary Beth Connolly Gibbons, Paul Crits-Christoph, and Bridget Hearon ppppppppppppp 93
Cost-Effective Early Childhood Development Programs from
Preschool to Third Grade
Arthur J. Reynolds and Judy A. Temple pppppppppppppppppppppppppppppppppppppppppppppppp109
Neuropsychological Rehabilitation
Barbara A. Wilson ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp141
Pediatric Bipolar Disorder
Ellen Leibenluft and Brendan A. Rich ppppppppppppppppppppppppppppppppppppppppppppppppppp163
Stress and the Hypothalamic Pituitary Adrenal Axis in the
Developmental Course of Schizophrenia
Elaine Walker, Vijay Mittal, and Kevin Tessner pppppppppppppppppppppppppppppppppppppppp189
Psychopathy as a Clinical and Empirical Construct
Robert D. Hare and Craig S. Neumann pppppppppppppppppppppppppppppppppppppppppppppppp217
The Behavioral Genetics of Personality Disorder
W. John Livesley and Kerry L. Jang pppppppppppppppppppppppppppppppppppppppppppppppppppp247
Disorders of Childhood and Adolescence: Gender and
Psychopathology
Carolyn Zahn-Waxler, Elizabeth A. Shirtcliff, and Kristine Marceau pppppppppppppppp275
vii
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Should Binge Eating Disorder be Included in the DSM-V? A Critical
Review of the State of the Evidence
Ruth H. Striegel-Moore and Debra L. Franko ppppppppppppppppppppppppppppppppppppppppp305
Behavioral Disinhibition and the Development of Early-Onset
Addiction: Common and Specific Influences
William G. Iacono, Stephen M. Malone, and Matt McGue ppppppppppppppppppppppppppp325
Psychosocial and Biobehavioral Factors and Their Interplay
in Coronary Heart Disease
Redford B. Williams pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp
349
Stigma as Related to Mental Disorders
Stephen P. Hinshaw and Andrea Stier pppppppppppppppppppppppppppppppppppppppppppppppppp367
Indexes
Cumulative Index of Contributing Authors, Volumes 1–4 ppppppppppppppppppppppppppp395
Cumulative Index of Chapter Titles, Volumes 1–4 pppppppppppppppppppppppppppppppppppp397
Errata
An online log of corrections to Annual Review of Clinical Psychology chapters (if any)
may be found at http://clinpsy.AnnualReviews.org
viii Contents
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