psychological processes. Relative to laboratory
research, EMA has the advantage of beingecological;
processes such as mood can be studied in subjects’
“natural habitats”where they are influenced by the
many environmental and interpersonal factors that
typify their lives but cannot be re-created in the
laboratory. Of course, EMA research can not only
sample the process of interest (e.g., mood) but also
characteristics of the environment (e.g., location,
time of day, presence of interpersonal conflict)
that change over time and that may be important
for explaining variation in the process of interest.
Thus, EMA studies can yield exceptionally rich
descriptive data.
Computerization represents another advantage
of EMA protocols over traditional field techniques.
Investigators have often collected field data using
paper diaries, asking subjects to complete one or
more diary entries per day between visits to the
study center. A chief limitation of this approach is
that investigators cannot be sure that the ratings
were completed at the times specified by the
research design. Subjects may neglect making
scheduled ratings and then“backfill”their diaries
before reporting to the study center to avoid admit-
ting they failed to make the scheduled ratings. To
the extent this backfilling occurs, it represents a
serious threat to the validity of the research. At
best, backfilling turns momentary reports into
covert retrospective reports, allowing them to be
influenced by the biases characteristic of retrospec-
tion (e.g., forgetting, self-presentation bias). Unfor-
tunately, because the practice of backfilling is
inherently deceptive, the investigator cannot
know to what extent these errors are present in
the data or how they vary from subject to subject.
Because EDs are computerized, EMA studies avoid
the backfilling problem. Subjects complete ratings
in response to prompts emitted by the device, and
entries are time-stamped by the computer. Non-
compliance, if it occurs, is recorded as such by the
absence of a completed assessment at the pro-
grammed prompt time. Backfilled entries, if sub-
jects tried to make them, would be time-stamped
and thus easily identified as questionable data.
A study of daily pain experiences (Stone,
Shiffman, Schwartz, Broderick, & Hufford, 2002)
provides dramatic evidence attesting to the advan-
tages of computerized assessments relative to
traditional paper diaries. The researchers passively
time-stamped paper diary recordings by inserting a
photocell in the cover of the diary binder to record
when it was opened. Results showed that only 11%
of the scheduled paper diary recordings were
completed at the appropriate times. However, sub-
jectsreportedcomplying with scheduled recording
95% of the time (i.e., they“hoarded”assessments
and backdated them to create an impression of
compliance). In contrast, a comparison group ofHandheld computers can be used to monitor and record
thoughts, emotions, and behaviors as they occur.
© 2010 Creatas Images/Jupiterimages CorporationBEHAVIORAL ASSESSMENT 273