Psychology

Research

Why Can’t We Be More Idiographic in Our Research? David H. Barlow1 and Matthew K. Nock2

1 Center for Anxiety and Related Disorders, Boston University, and

2 Harvard University

ABSTRACT—Most psychological scientists make inferences

about the relations among variables of interest by

comparing aggregated data from groups of individuals.

Although this method is unarguably a useful one that will

continue to yield scientific advances, important limitations

exist regarding the efficiency and flexibility of such de-

signs, as well as with the generality of obtained results.

Idiographic research strategies, which focus on the

intensive study of individual organisms over time, offer a

proficient and flexible alternative to group comparison

designs; however, they are rarely taught in graduate

training programs and are seldom used by psychological

scientists. We highlight some of the unique strengths of

idiographic methods, such as single case experimental

designs, and suggest that psychological science will prog-

ress most efficiently with an increased use of such methods

in both laboratory and clinical settings.

Edward Tolman said to Gordon Allport ‘‘I know I should be more

idiographic in my research, but I just don’t know how to be,’’ to

which Allport replied, ‘‘Let’s learn!’’ (Allport, 1962, p. 414).

This sentiment was based on the fact that, whether it’s a labo-

ratory rat or a patient in the clinic with a psychological disorder,

it is the individual organism that is the principle unit of analysis

in the science of psychology. The intensive study of the

individual is associated with a hallowed tradition in scientific

psychology. Indeed, the founders of experimental psychology

including Fechner, Wundt, Ebbinghaus, and Pavlov studied

individual organisms with scientific approaches that would be

considered internally valid, and they strengthened these find-

ings (and began to establish generality) through replication in

other organisms (see Barlow, Nock, & Hersen, 2008).

This scientific strategy, which is fully capable of establishing

causal relations among variables, came to be known as the

idiographic approach. Gordon Allport, in his area of social

psychology, argued eloquently that the science of psychology

should attend to the uniqueness of the individual organism

(Allport, 1962). Routed deep in the structural school of

psychology, this approach also was popular in more applied

branches in psychology in the middle of the last century.

Perhaps the biggest champion of an idiographic approach in

clinical settings was Shapiro, who was advocating a scientific

approach to the study of individuals with psychopathology as

early as 1951 (e.g., Shapiro 1961, 1966). The idiographic

approach perhaps reached its zenith in psychological science

with the work of B.F. Skinner. In a famous quote, Skinner (1966)

noted: ‘‘. . . instead of studying a thousand rats for one hour each

or a hundred rats for ten hours each the investigator is more

likely to study one rat for a thousand hours’’ (p. 21). Thus,

Skinner and his colleagues in the animal laboratories are largely

credited with developing and refining an experimental

idiographic approach that came to be known as the experimental

analysis of behavior.

This idiographic approach represents a true scientific

undertaking, as independent variables are manipulated in the

context of carefully measured and repeatedly assessed depen-

dent variables. This is in contrast to the alternative nomothetic

experimental strategy, in which the researcher looks to assemble

relatively large groups of individual organisms and, in the most

straightforward application, examines the average response of

the group to the introduction of some manipulation compared

with the response to well-construed control conditions. The

major differences between the idiographic and nomothetic

traditions are, of course, approaches to intersubject variability

and the generality of findings. As variability is often consider-

able among organisms, the task of any psychological scientist is

to discover functional relations among independent variables

over and above the welter of environmental and biological

variables influencing the organism at any given point in time. A

nomothetic approach makes an implicit assumption that much of

Address correspondence to David H. Barlow, Center for Anxiety and Related Disorders, Boston University, 648 Beacon Street, 6th Floor, Boston, MA 02215; e-mail: [email protected].

P E R S P E C T I V E S O N P S Y C H O L O G I C A L S C I E N C E

Volume 4—Number 1 19Copyright r 2009 Association for Psychological Science

this variability is intrinsic to the organism and uses sophisti-

cated data analytic procedures to look for reliable effects over

and above this ‘‘error.’’ Significant effects are then assumed to be

more or less generalizable based on the number of individuals

included in the experimental group and the representativeness

of the population of such individuals (i.e., the use of random

sampling).

Of course, random sampling is seldom achieved in psycho-

logical research where, indeed, the goal is more often to strive

for homogeneous samples in which the generality of findings can

be very limited. Sidman (1960) made the following point a

number of years ago when discussing approaches to variability:

The rationale for statistical immobilization of unwanted variables

is based on the assumed random nature of such variables. In a

large group of subjects, the reasoning goes, the uncontrolled factor

will change the behavior of some subjects in one direction and will

affect the remaining subjects in the opposite away. When the data

are averaged over all the subjects, the effects of the uncontrolled

variables are presumed to add algebraically to zero. The composite

data are then regarded as though they were representative of one

ideal subject who had never been exposed to the uncontrolled

variables at all. (p. 162)

Addressing the issue of the generality of findings, Sidman

wrote the following:

Tracking down sources of variability is then a primary technique

for establishing generality. Generality and variability are basically

antithetical concepts. If there are major undiscovered sources of

variability in a given set of data, any attempt to achieve subject or

principle generality is likely to fail. Every time we discover and

achieve control of a factor that contributes to variability, we

increase the likelihood that our data will be reproducible with new

subjects and in different situations. Experience has taught us that

precision of control leads to more extensive generalization of data.

(p. 152)

Although the use of the idiographic approach led to signifi-

cant advances in the earliest days of laboratory-based experi-

mental psychology, as well as during early translations of

findings from psychological science to clinical applications in

the middle of the last century, it is clear that the nomothetic

strategy has become a dominant method to establish both

internal and external validity over the past few decades (Kazdin,

2003; Nock, Janis, & Wedig, 2008). One reason for this devel-

opment in applied settings was the beginning of funding of large

randomized clinical trials (RCTs) by the National Institutes of

Health.

Many such studies require 10 or more years and many

millions of dollars to perform one treatment trial. For instance,

the National Institutes of Mental Health (NIMH) funded

the treatment of depression collaborative research program

(Elkin et al., 1989). This study, which took 13 years to finish

(1977–1990), was reminiscent of earlier efforts such as the

Cambridge Somerville Youth Study conducted from 1935

through 1951, which divided delinquent boys into two groups—

one treatment group and one group that received ‘‘treatment as

usual’’ (McCord, 1978). The fact that there were no effects at 5,

10, 20, or 30 years did much to discourage efforts of this

type for at least the next 30 years. In fact, results from the NIMH

depression collaborative trial were not particularly revealing

either, as no significant differences existed among treatment

and comparison groups at any point in time. Nevertheless,

this trial provoked useful comment and a great deal of

controversy about strategic issues and the potential for

improvement in the methodology of RCTs. These trials have

improved to the point where they have become ‘‘the

gold standard’’ for establishing causal relations between inde-

pendent and dependant variables more generally, and data

emanating from these trials have deep influences on health care

practices (Barlow, 2004).

But is something still lacking? Scientifically, relying on a

relatively small group of researchers requiring enormous

amounts of time and resources to perform a single treatment trial

can be seen as an inefficient method of advancing knowledge. In

applied clinical settings, clinicians often question the applica-

bility of findings from RCTs to individuals seen in typical

clinical settings. In other words, there is a strong perception

that problems exist in generalizing a nomothetic result to an

idiographic situation. The variety of forms that these arguments

take are often cast as specific objections to RCT methodology,

and these arguments have been detailed numerous times in

the past decade (e.g., Persons & Silberschatz, 1998; Westen,

Novotny, & Thompson-Brenner, 2004).

Rather than simply critiquing nomothetic methodologies, can

we enrich these methodologies with a complementary focus on

the individual? The fact is that we have a good idea of how to be

more idiographic in our research. Although most psychological

researchers have been trained in group comparisons designs and

have relied primarily on them, exciting advances have been

made in the use of idiographic methodologies, such as the

single-case experimental design (see Barlow et al., 2008).

The flexibility and efficiency of these designs make them ideally

suited for use by psychological scientists, clinicians, and

students alike, given that they require relatively little time and

few resources and subjects and yet they can provide strong

evidence of causal relations between variables.

The time now seems right to put more emphasis on idiographic

strategies that can be integrated in a healthy way into existing

nomothetic research approaches in both clinical and basic

science settings. In clinical science, having established the

effectiveness of a particular independent variable (e.g., an in-

tervention for a specific form of psychopathology), one could

then carry on with more idiographic efforts tracking down

sources of intersubject variability and isolating factors respon-

sible for this variability (Kazdin & Nock, 2003; Nock, 2007).

Necessary alterations in the intervention protocols to effectively

20 Volume 4—Number 1

Why Can’t We Be More Idiographic in Our Research?

address variability could then be tested, once again idiograph-

ically, and incorporated into these treatments. Researchers in

basic science laboratories could undertake similar strategies

and avoid tolerating large error terms. Thus, all of psychological

science, both basic and applied, would benefit.

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Elkin, I., Shea, M.T., Watkins, J.T., Imber, S.D., Sotsky, S.M., Collins,

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Kazdin, A.E. (2003). Research design in clinical psychology (4th ed.). Boston: Allyn & Bacon.

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Psychological Bulletin, 130, 631–663.

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David H. Barlow and Matthew K. Nock