Editing Psychometrics (section)

== Historical foundation ==
Psychological testing has come from two streams of thought: the first, from [[Charles Darwin|Darwin]], [[Sir Francis Galton|Galton]], and [[James McKeen Cattell|Cattell]], on the measurement of individual differences and the second, from [[J.E. Herbart|Herbart]], [[E.H. Weber|Weber]], [[Gustav Fechner|Fechner]], and [[Wundt]] and their psychophysical measurements of a similar construct. The second set of individuals and their research is what has led to the development of [[experimental psychology]] and standardized testing.<ref name="Kaplan, R.M. 2010">Kaplan, R.M., & Saccuzzo, D.P. (2010). ''Psychological Testing: Principles, Applications, and Issues.'' (8th ed.). Belmont, CA: Wadsworth, Cengage Learning.</ref>

=== Victorian stream ===
Charles Darwin was the inspiration behind Francis Galton, a scientist who advanced the development of psychometrics. In 1859, Darwin published his book ''[[On the Origin of Species]]''. Darwin described the role of natural selection in the emergence, over time, of different populations of species of plants and animals. The book showed how individual members of a [[species]] differ among themselves and how they possess characteristics that are more or less adaptive to their environment. Those with more adaptive characteristics are more likely to survive to procreate and give rise to another generation. Those with less adaptive characteristics are less likely. These ideas stimulated Galton's interest in the study of human beings and how they differ one from another and how to measure those differences.

Galton wrote a book entitled ''[[Hereditary Genius]]'' which was first published in 1869. The book described different characteristics that people possess and how those characteristics make some more "fit" than others. Today these differences, such as sensory and motor functioning (reaction time, visual acuity, and physical strength), are important domains of scientific psychology. Much of the early theoretical and applied work in psychometrics was undertaken in an attempt to measure [[intelligence (trait)|intelligence]]. Galton often referred to as "the father of psychometrics," devised and included mental tests among his [[anthropometric]] measures. [[James McKeen Cattell]], a pioneer in the field of psychometrics, went on to extend Galton's work. Cattell coined the term ''mental test'', and is responsible for research and knowledge that ultimately led to the development of modern tests.<ref name = "kap">Kaplan, R.M., & Saccuzzo, D.P. (2010). ''Psychological testing: Principles, applications, and issues'' (8th ed.). Belmont, CA: Wadsworth, Cengage Learning.</ref>

=== German stream ===
The origin of psychometrics also has connections to the related field of [[psychophysics]]. Around the same time that Darwin, Galton, and Cattell were making their discoveries, Herbart was also interested in "unlocking the mysteries of human consciousness" through the scientific method.<ref name = "kap"/> Herbart was responsible for creating mathematical models of the mind, which were influential in educational practices for years to come.

[[Ernst Heinrich Weber|E.H. Weber]] built upon Herbart's work and tried to prove the existence of a psychological threshold, saying that a minimum stimulus was necessary to activate a [[Sensory nervous system|sensory system]]. After Weber, [[Gustav Fechner|G.T. Fechner]] expanded upon the knowledge he gleaned from Herbart and Weber, to devise the law that the strength of a sensation grows as the logarithm of the stimulus intensity. A follower of Weber and Fechner, [[Wilhelm Wundt]] is credited with founding the science of psychology. It is Wundt's influence that paved the way for others to develop psychological testing.<ref name = "kap"/>

=== 20th century ===
In 1936, the psychometrician [[L. L. Thurstone]], founder and first president of the Psychometric Society, developed and applied a theoretical approach to measurement referred to as the [[law of comparative judgment]], an approach that has close connections to the psychophysical theory of [[Ernst Heinrich Weber]] and [[Gustav Fechner]]. In addition, Spearman and Thurstone both made important contributions to the theory and application of [[factor analysis]], a statistical method developed and used extensively in psychometrics.<ref>Nunnally, J., & Berstein, I. H. (1994). ''Psychometric theory'' (3rd ed.). New York: McGraw-Hill.</ref> In the late 1950s, [[Leopold Szondi]] made a historical and epistemological assessment of the impact of statistical thinking on psychology during previous few decades: "in the last decades, the specifically psychological thinking has been almost completely suppressed and removed, and replaced by a statistical thinking. Precisely here we see the cancer of testology and testomania of today."<ref>[[Leopold Szondi]] (1960) ''Das zweite Buch: Lehrbuch der Experimentellen Triebdiagnostik''. Huber, Bern und Stuttgart, 2nd edition. Ch.27, From the Spanish translation, B)II ''Las condiciones estadisticas'', p.396. Quotation: {{quotation|el pensamiento psicologico especifico, en las ultima decadas, fue suprimido y eliminado casi totalmente, siendo sustituido por un pensamiento estadistico. Precisamente aqui vemos el cáncer de la testología y testomania de hoy.}}</ref>

More recently, psychometric theory has been applied in the measurement of [[wikt:personality|personality]], [[Attitude (psychology)|attitudes]] and [[belief]]s, and [[academic achievement]]. These latent constructs cannot truly be measured, and much of the research and science in this discipline has been developed in an attempt to measure these constructs as close to the true score as possible. 

Figures who made significant contributions to psychometrics include [[Karl Pearson]], Henry F. Kaiser, [[Carl Brigham]], [[L. L. Thurstone]], [[E. L. Thorndike]], [[Georg Rasch]], [[Eugene Galanter]], [[Johnson O'Connor]], [[Frederic M. Lord]], [[Ledyard R Tucker]], [[Louis Guttman]], and [[Jane Loevinger]].