The tagline of the Psychometric Society says that the Society is
devoted to the advancement of quantitative measurement practices
in psychology, education and the social sciences. This is a very
general description of psychometrics, but we emphasize the word
quantitative in the previous sentence. Some people take
a more clinical view of psychometrics, emphasizing the
administration and application of psychological scales. But scale
administration is not a particular emphasis of this society.
As a way to elucidate our definitions and perspectives on the
term psychometrics, a few psychometricians with
different research orientations have provided definitions below.
These definitions are by no means official but they rather
demonstrate the individual differences in the way
psychometricians think about their profession.
Henk
Kelderman (Leiden University, VU Amsterdam)
Measurement and quantification is ubiquitous in modern society.
In early modernity, the scientific revolution provided a firm
scientific basis for physical measures like temperature,
pressure, and so on. In the late nineteenth and early twentieth
century, a similar revolution took place in psychology with the
measurement of intelligence and personality. A crucial role was
played by Psychometrics, initially defined as “The art of
imposing measurement and number upon operations of the mind”
(Galton, 1879, p149). Since 1936 the Psychometric Society has
been at the forefront of the development of formal theories and
methods to study the appropriateness and fidelity of
psychological measurements. Because measurement in psychology is
often done with tests and questionnaires, it is rather imprecise
and subject to error. Consequently, statistics plays a major role
in psychometrics. For example, members of the society have
devoted much attention to the development of statistical methods
for the appraisal of noisy measurements whose outcomes are
considered indicators of attributes of interest that can not be
directly observed.
Today, psychometrics covers virtually all statistical methods
that are useful for the behavioral and social sciences including
the handling of missing data, the combination of prior
information with measured data, measurement obtained from special
experiments, visualization of statistical outcomes, measurement
that guarantees personal privacy, and so on. Psychometric models
and methods now have a wide range of applicability in various
disciplines such as education, industrial and organizational
psychology, behavioral genetics, neuropsychology, clinical
psychology, medicine, and even chemistry.
In the future we will have more personal data then ever before
thanks to improved instrumentation, like brain scanning and
genome sequencing, as well as the growth of the internet and
computing power. Data collection now surpasses our ability to
harvest and interpret its complexity. It is expected that whole
economies will grow around the analysis of data, both commercial
and scientific. The importance of innovations in measurement and
statistics and ways to meaningfully summarize and visualize data
is expected to grow along with it. The Psychometric Society is
geared up to be a major player in providing these innovations.
Galton, F. (1879). Psychometric experiments. Brain: A
Journal of Neurology, 11, 149-162.
Peter Molenaar (Pennsylvania State University)
Psychometrics is the approximation of latent psychological
processes by means of stochastic analysis at both the individual
and population levels.
Psychometrics is a scientific discipline concerned with the
construction of assessment tools, measurement instruments, and
formalized models that may serve to connect observable phenomena
(e.g., responses to items in an IQ-test) to theoretical
attributes (e.g., intelligence). For example, theoretical
constructs have been defined as domains of observable behaviors
of which item responses form a sample (generalizability theory),
as psychological attributes that act as common causes of item
responses (latent variable theory), as expected values of a test
score (classical test theory), as mappings of observable
relations into a numerical system (scaling theory), and as
systems of mutually reinforcing factors (network theory). Such
models present conceptual, substantive, and statistical problems
that psychometricians aim to analyze and solve. Because many of
the questions that psychometricians study transcend disciplinary
boundaries, and concern general issues of measurement and
data-analysis, the boundaries of the discipline are fuzzy;
psychometrics is especially closely intertwined with methodology
and statistics. Psychometric techniques are widely used across
the sciences, and have found applications in educational testing,
behavior genetics, sociology, political science, and
neuroscience.
David Thissen (University of North Carolina at Chapel Hill)
The use of the adjective “psychometric” in the sense of the name
of the Psychometric Society dates back at least to Francis
Galton’s (1879) essay in Brain entitled “Psychometric
Experiments”; the opening line of that article is that
“Psychometry, it is hardly necessary to say, means the art of
imposing measurement and number upon operations of the mind …”
Galton’s “experiments” were essentially introspective, but he
treated their results “statistically” (meaning he reported
counts; it was, after all 1879!). The words “psychometric” as an
adjective and “psychometrics” as a noun referring to the field of
study came into increasingly common use as psychology developed,
reaching prominence as the name of the subdiscipline with the
foundation of the Psychometric Society in 1935 and the
publication of Guilford’s (1936) Psychometric Methods.
Guilford’s (1936) Psychometric Methods covered a wide variety of
topics, from psychophysical methods and psychological scaling
through correlation and regression to procedures for the analysis
of data arising from mental tests, and factor analysis. In the
preface, Guilford (1936, p. xi) wrote “The name “Psychometric
Methods,” too long restricted to clinical tests and the like, is
surely broad enough to encompass appropriately all the topics
just mentioned.” The journal of the Psychometric Society, called
Psychometrika, spelled with a k (presumably) with a nod toward
Galton and Pearson’s similarly-named Biometrika), began
publication with the foundation of the society; it included
articles on all of the topics in Guilford’s book. For most of the
twentieth century, psychometrics was defined well by the
subheading that appeared under the title of Psychometrika from
its inception in 1936 until a cover redesign in 1984, “a journal
devoted to the development of psychology as a quantitative
rational science.”
The practitioners of the science of psychometrics were known as
psychometricians; however, that term was also used to refer to
practitioners who administered psychological tests in educational
and clinical practice. Around 1980, psychometric graduate
training programs began to change their names to avoid confusion
with that alternative meaning, and to be more inclusive of an
ever-increasing scope; most often the nomenclature used was
“quantitative psychology.” In 1984, the cover of Psychometrika
was redesigned, for the first time setting aside Thurstone’s
hand-ruled cover art; the time-honored title was retained, but
the subheading was changed to read “a journal of quantitative
psychology.” The field is now most often referred to as
“quantitative psychology” but its flagship journal remains
Psychometrika. Jones and Thissen (2007; see below) summarize the
history of the subdiscipline in the opening chapter of a
relatively recent book entitled, curiously enough, Psychometrics.
Galton, F. (1879). Psychometric experiments. Brain: A
Journal of Neurology, 11, 149-162.
Guilford, J.P. (1936). Psychometric Methods. New
York, NY: McGraw-Hill Book Company.
Videos and Further Reading
Video lectures can be found here.
More information on the definition, history and the future
of psychometrics can be found in the following papers.
Jones, L. V., & Thissen, D. (2007). A
history and overview of psychometrics. In C.R. Rao and S.
Sinharay (eds). Handbook of Statistics, 26:
Psychometrics (pp.1-27). Amsterdan: North Holland.
A free version of this chapter can be obtained here.
Stout, W. (2002). Psychometrics: From
practice to theory and
back. Psychometrika, 67(4), 485-518. A
free version of this paper can be obtained here.
Groenen, P. J., & Andries van der Ark, L. (2006). Visions
of 70 years of psychometrics: the past, present, and
future. Statistica Neerlandica, 60(2),
135-144.
Borsboom, D. (2006). The attack of
the psychometricians. Psychometrika,71(3),
425-440.
