Single-subject research involves intensively studying a small number of participants to focus on individual behavior over time. It has been used in psychology since its beginnings. Some key features include repeatedly measuring a dependent variable under different conditions designated by letters (e.g. A, B, C). Researchers wait for steady responding before changing conditions. Common designs are reversal/ABA designs where a baseline is compared to a treatment condition, and multiple-baseline designs where the treatment is introduced at different times across subjects, behaviors, or settings. Data is typically graphed and analyzed visually for changes in level, trend or latency. Advantages include flexibility, ability to see quick effects of treatments, and strong conclusions about variable control. Disadvantages include

1. Single Subject
Design
Made by
psychologist
Stella

2. History of Studying the Individual
 Psychology, though, actually began with intensive, prolonged study of
the individual. This single-participant research strategies followed
from the earlier scientific paradigms employed by physiologists.
 The individual approach of Gustav Fechner in 1860 had earth-shaking
consequences for the development of a new science of psychology
when he developed our methods of psychophysics and also
formalized Weber’s famous law.
 Ivan Pavlov who studied the long-term conditioning history of his
dogs to provide us with our contemporary principles of conditional
responses.
 Wihelm Wundt and other early psychologists studied mental
processes under one or more sequential conditions, all within the
same person.
 Hermann Ebbinghaus (1913) early use of single-subject resarch in
psychology.

3. Single-Subject research
 Single-subject research—which involves testing a small number of
participants and focusing intensively on the behaviour of each
individual—is an important alternative to group research in
psychology.
 Single-subject studies must be distinguished from case studies, in
which an individual case is described in detail. Case studies can be
useful for generating new research questions, for studying rare
phenomena, and for illustrating general principles. However,
they cannot substitute for carefully controlled experimental or
correlational studies because they are low in internal and
external validity.
 Single-subject research has been around since the beginning of the
field of psychology. Today it is most strongly associated with the
behavioural theoretical perspective, but it can in principle be
used to study behaviour from any perspective.

4. General Features of Single-
Subject Designs
 First, the dependent variable (represented on the y-
axis of the graph) is measured repeatedly over time
(represented by the x-axis) at regular intervals.
 Second, the study is divided into distinct phases, and
the participant is tested under one condition per
phase. The conditions are often designated by capital
letters: A, B, C, and so on.
 The conditions are often designated by capital
letters: A, B, C, and so on. Thus Figure represents a
design in which the participant was tested first in one
condition (A), then tested in another condition (B),
and finally retested in the original condition (A).

5. General Features of Single-Subject Designs
 Another important aspect of single-subject research is that the
change from one condition to the next does not usually occur
after a fixed amount of time or number of observations.
Instead, it depends on the participant’s behaviour.
 Specifically, the researcher waits until the participant’s
behaviour in one condition becomes fairly consistent from
observation to observation before changing conditions. This
is sometimes referred to as the steady state strategy (Sidman,
1960)

6. Reversal Designs
 The most basic single-subject research design is the reversal
design, also called the ABA design.
 During the first phase, A, a baseline is established for the
dependent variable. This is the level of responding before any
treatment is introduced, and therefore the baseline phase is a kind of
control condition.
 When steady state responding is reached, phase B begins as the
researcher introduces the treatment. There may be a period of
adjustment to the treatment during which the behaviour of interest
becomes more variable and begins to increase or decrease.
 Again, the researcher waits until that dependent variable reaches
a steady state so that it is clear whether and how much it has
changed. Finally, the researcher removes the treatment and again
waits until the dependent variable reaches a steady state. This
basic reversal design can also be extended with the reintroduction
of the treatment (ABAB), another return to baseline (ABABA),
and so on.

7. Reversal Designs
Figure: ABAB Reversal Design

8. Multiple-Baseline Design
 Sometimes, a researcher may be interested in addressing
several issues for one student or a single issue for several
students. In this case, a multiple-baseline design is used.
 “In a multiple baseline across subjects design, the researcher
introduces the intervention to different persons at
different times. The significance of this is that if a behavior
changes only after the intervention is presented, and this
behavior change is seen successively in each subject’s
data, the effects can more likely be credited to the
intervention itself as opposed to other variables.
 Multiple-baseline designs do not require the intervention
to be withdrawn. Instead, each subject’s own data are
compared between intervention and non-intervention
behaviors, resulting in each subject acting as his or her
own control (Kazdin, 1982).

9. Multiple-Baseline Design
 An added benefit of this design, and all single-case designs,
is the immediacy of the data. Instead of waiting until post-
intervention to take measures on the behavior, single-case
research prescribes continuous data collection and
visual monitoring of that data displayed graphically,
allowing for immediate instructional decision-making.
 In a multiple-baseline design, baselines are established for
different participants, different dependent variables, or
different settings—and the treatment is introduced at a
different time on each baseline. If the introduction of the
treatment is followed by a change in the dependent variable
on each baseline, this provides strong evidence of a treatment
effect.

10. Multiple-Baseline Design

11. Data Analysis in Single-
Subject Research
 Single-subject researchers typically analyze their
data by graphing them and making judgments
about whether the independent variable is
affecting the dependent variable based on level,
trend, and latency.

12. Advantage of Single-Subject Research
 Group means could conceal patterns that appear in
individuals' data.
 Big effects - only clinically significant effects are
likely to be found.
 Ethical and practical advantages (eg; can not
withhold treatment; too few subjects).
 Flexibility.

13. Advantage of Single-Subject Research
 Those who use the single-subject approach find it both a
powerful and satisfying research method. One reason for
this is that the method provides feedback quickly to the
investigator about the effects of the treatment
conditions. The experimenter knows relatively soon whether
the treatment is working or not working. Day-to-day
changes can be observed first hand, quickly and in
individual participants. In contrast to the single-subject
approach, a large sample statistical approach may take
weeks or months of testing participants, calculating
means, then performing statistical analyses, etc., and
unfortunately, often nothing may be known about the effects
of the treatment conditions until the final statistical analysis is
complete

14. Advantage of Single-Subject Research
 The single-subject method also allows us to draw strong
conclusions regarding the factors controlling the
dependent variable, yet the method does not use random
assignment. The method allows strong conclusions
because investigators employing it use procedures that
provide rigorous control over environmental-
experimental conditions with great emphasis on obtaining
stable behavior with each participant. To be an acceptable
scientific work, the research must demonstrate for each
participant that behavior is controlled by the treatment
condition and he or she must also show both intra- and
inter-participant replication. That is, control must be
shown both within a single participant and also between the
participants.

15. Disadvantage of Single-Subject Research
 Can not examine any between-subject effects.
 Can not detect small effects.
 May be less generalizable.

16. Disadvantage of Single-Subject Research
 One obvious limitation of the single-subject approach is that
the method is unsuitable for answering actuarial types of
questions. Questions such as, "How many of the one-
hundred people exposed to a particular treatment will
respond favorably and how many will respond
unfavorably?" A similar question relates to studies
comparing two or more different treatments on the same
behavioral measure. For example, which of the various
treatments is the most effective? Ineffective?
Debilitating? The method cannot be used if you are
interested in treating an entire group of participants,
such as a classroom, in an identical way on a daily basis, i.e.,
when changes in procedures are made, they are made for
everyone in the group at the same time and for the same
period. A different method is also required if "after the
fact" studies (ex post facto, correlational, passive
observational) are of interest.

17. Disadvantage of Single-Subject Research
 Single-subject approach makes heavy time demands.
Establishing a criterion and acquiring stable baselines for the
response of interest are sometimes very difficult. Further,
determining whether variability in behavior is intrinsic or
extrinsic can be troublesome. Non-reversible (irreversible)
behavior poses its own set of problems and it precludes the
use of a design in which the researcher removes the treatment to
observe a return to baseline levels of responding. Failure to
obtain intra- and inter-participant replication for whatever
reason creates problems for the single subject approach.
Sometimes decisions regarding the necessary number of
both intra- and inter-participant replications are largely
subjective.
Nevertheless, in spite of the limitations and problems described
here, the single-subject method does provide researchers
with another powerful way to assess behavior.

18. Reference
 http://condor.depaul.edu/dallbrit/extra/psy242/242-
single-subject.htm
 https://knowledgesociety.usal.es/sites/default/files/Si
ngle%20Subject%20and%20Time%20Series%20Desig
ns.pdf
 https://opentextbc.ca/researchmethods/chapter/singl
e-subject-research-designs/

19. Thank You
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