History & Philosophy of Psychology (2011) Vol. 13(2), 32–39.

The Idiographic / Nomothetic Dichotomy: Tracing Historical Origins of Contemporary Confusions Oliver C. Robinson University of Greenwich Abstract The relevance of idiographic and nomothetic forms of science has been the subject of fierce debates within psychology, and there has been a false tendency to see these two terms as antagonistic rather than complementary. The origins of contemporary confusions over the term ‘nomothetic’ stem from a long-held misconception that nomothetic research requires large samples and group-based statistics such as means and variances (i.e. the ‘Galtonian’ paradigm), when in fact nomothetic research has another paradigm at its disposal that can be termed the ‘Wundtian’ paradigm, which relies on smaller samples, and a case-by-case form of analysis (Lamiell, 2003). Meanwhile, the historical origins of confusion over the term ‘idiographic’ stem from an enduring but incorrect sense that it is opposed to nomothetic inquiry, combined with an increasing tendency to use the word in ways that bear no relation to its original meaning. The contemporary situation could be substantially improved if Psychology was to re-locate the Wundtian model back to its rightful central position in the discipline. Keywords: idiographic, nomothetic, history, single-case, case-study

Every snowflake is unique, as is every wave in the sea. Yet all snowflakes, like all waves, are governed by the same immutable laws of nature. Human beings are like this too. (Marinoff, 2003)

In the late nineteenth century, the German philosopher Wilhelm Windelband coined the two words ‘idiographic’ and ‘nomothetic’ to refer to different forms of evidence-based knowledge (Windelband 1894/1990). Idiographic knowledge aims at describing and explaining particular phenomena (Windelband, 1901/2001). Nomothetic knowledge, on the other hand, has the aim of finding generalities that are common to a class of particulars and deriving theories or laws to account for these generalities. These two words entered American psychology thanks to the philosopher/psychologist James Hayden Tufts, who was well versed in Windbelband’s philosophy (Tufts, 1895). The origins of confusion over the term ‘nomothetic’ Hugo Münsterberg, the seventh president of the American Psychological Society, referred to the idiographic / nomothetic distinction in an address to the APA, later printed in Psychological Review (Münsterberg, 1899). He warned psychologists

The Idiographic / Nomothetic Dichotomy 33

against interpreting the terms as implying that individuals and theory are in some sense opposed (Franck, 1982). He suggested that the individual particulars and general theory are complementary sides of all science, for example history is concerned with both specific events and explanatory theory, and natural scientists aim both at the development of theory and the study of highly particularised phenomena. Münsterberg suggested that the individual case should be central to theory development and testing in the emerging discipline of psychology. For thirty years after Münsterberg’s paper, the individual case was a common sight in psychology journals, as findings were frequently presented as a series of cases. This was true of both the early experimental quantitative psychologists, such as Ebbinghaus (1885/1913), Pavlov (1927), Cattell (1886), Titchener (1905), Thorndike (1911) and Watson and Rayner (1920), and was also true of early qualitative, observational or clinical research by Kraepelin (1895), Freud (1909), James (1902/2002), Alzheimer (1911) and Piaget (1923). All employed a ‘case-by-case’ research approach that both drove and tested theory. This approach can be referred to as the Wundtian methodological model (Danziger, 1990; Lamiell, 2003). In this approach, individuals are studied and analysed one at a time, in order to search for generalities that apply to all individuals within the sample (Shapiro, 1966). A typical early example of the Wundtian approach was Pavlov’s book Conditioned Reflexes, in which each table shows how one dog reacts under different experimental conditions (Pavlov, 1927). Lamiell describes the overall rationale of the Wundtian model as follows:

...the quest for knowledge of general laws governing individual psychological functioning would have been seen not only as permitting an “N = 1” approach but also as logically demanding it, for there would have been no way to determine if a putative law were in fact common to all, allen gemein, except by investigating the matter case by case, one research “subject” at a time. (Lamiell, 2003, p.33) In the 1930s Gordon Allport (one of Münsterberg’s pupils at Harvard)

popularised the adoption of the idiographic / nomothetic distinction in psychology by equating each term with a particular research method in the study of personality, but changed their meaning as a result (Allport, 1937; Hurlburt & Knapp, 2006). Allport pinned the label nomothetic to the group-based methodology that had been devised in the intelligence testing and heredity research of Galton (1889), Pearson (1896) and Spearman (1904), and was gaining popularity across psychology at the time. This ‘Galtonian’ methodology combined cases into aggregated group samples for statistical analysis purposes, and presented data at the level of the group (Danziger, 1990; Lamiell, 2003). In the Galtonian approach, which we now recognise as the standard quantitative model of contemporary psychology, data is collected for a group of cases, or into multiple groups (e.g. experimental / control), and then each group is analysed as a whole, using cross-case statistics such as frequencies, means, standard deviations, variance and correlation coefficients. Group parameters, rather than individual cases, are the key units of analysis in this form of research, and significance testing will pertain to effects observed at the group level to explore relationships between variables or in an experiment to infer cause-and-effect by viewing group-level differences between experimental group and control group.

34 Oliver C. Robinson

This method was given additional support in the 1930s by the development of inferential group-based statistics developed by the agricultural statistician R.A. Fisher (1925), which then developed into the General Linear Model, upon which are based many key statistical treatments for grouped psychological data such as the ANOVA and regression analysis (Barlow & Hersen,1984).

Allport thought that this group-based research in personality psychology was what Windelband had in mind when he referred to nomothetic science. In Allport’s formulation of idiographic / nomothetic, the Galtonian group-based approach was given the label of nomothetic science, while the Wundtian case-by-case approach was omitted. It was about this same time that the Wundtian model disappeared from much of psychology. For decades it became confined to N=1 experimentalists working in the operant tradition, following B.F.Skinner, who had publicly disavowed the group-based Galtonian heterodoxy:

A prediction of what the average individual will do is often of little or no value in dealing with a particular individual… In general a science is helpful in dealing with the individual only insofar as its laws refer to individuals. A science of behaviour which concerns only the behaviour of groups is not likely to be of help in our understanding of the particular case. (Skinner, 1953, p.19)

Windelband’s conception of nomothetic was in fact closer to the Wundtian / Skinnerian approach than the Galtonian methodological model (Lamiell, 1998). Windelband used the term ‘algemein’ to refer to nomothetic findings, which means common to all, and this parallels the Wundtian model’s objective to establish laws and theory that are common to all individuals in a particular sample, and potentially all individuals in a class. In the Galtonian model, generalisations are made about the group as an aggregate whole, such as a difference between group means, a structural equation model or a factor analytic model. These findings do not necessarily pertain to particular individuals within the group, as individuals may not reflect the group’s tendency (Bakan, 1967).

So there are in fact two distinct forms of nomothetic endeavour available to psychology – one to establish what is common to all individuals in a sample or category (the Wundtian model), and the other to establish what is common to a sample or group of persons as an aggregated whole (the Galtonian model). It is the Wundtian approach that employs individual cases in theory development and theory testing, as in order to make a ‘common to all’ claim, a researcher must look at all cases in a sample, one at a time, to establish the same pattern within each (Bakan, 1967, Kazdin, 1982). The theory that results from this painstaking process can be tested on any individual within the class to which the theory is said to apply, for the theory predicts what is common to all, and if one individual does not conform, this is a challenge to the theory. If predictions about single cases are repeatedly not borne out then the theory may be falsified (Flyvbjerg, 2006; Mook, 1983; Popper, 1972). This is quite different from predictions made within the Galtonian model, which are made about a group as an aggregated whole, and therefore must be tested at that group level. The origins of confusion over the term ‘idiographic’ Allport, as previously mentioned, was the great populariser of the idiographic / nomothetic distinction in psychology. Being a personality theorist, he gave the label

The Idiographic / Nomothetic Dichotomy 35

of idiographic to case-study research that focused on describing individual personalities in-depth (Allport, 1937). His intention in introducing the concepts of idiographic and nomothetic research into psychology was to legitimise the study of the individual person in both theory and therapy by equating it with a particular epistemology (Allport, 1961; Allport, 1962; Levine, Sandeen & Murphy, 1992); however it seemed to have the reverse effect. The idiographic/nomothetic distinction spread rapidly across a psychology that was searching for scientific foundations, and had found it in the group-based Galtonian approach that had been rather flatteringly equated with nomothetic science (e.g. Du Mas, 1955). Despite Allport’s intentions, the polarity came to be construed as antagonistic rather than complementary, and idiographic research came to be construed as the antiscientific adversary of nomothetic progress. Thus when Beck (1953) raised the titular question in an article in Psychological Review: “The Psychology of Personality: Nomothetic or Idiographic?”, Hans Eysenck (1954) felt compelled to respond with an article “The Psychology of Personality: Nomothetic!”, describing what he saw as opposing views.1 This continued for some decades; for example in the 1960s Holt (1962) stated that the idiographic method was an artistic, not scientific, approach and had no place in psychology. Still in the 1970s and 1980s writers were denouncing idiographic methods as unscientific and opposed to nomothetic science (e.g. Kimble, 1984; Nunnally, 1978).

The notion of idiographic methods has, in the last ten years, enjoyed a revival. However, the use of the term in journal articles across the last decade shows a plurality of different meanings, many of which bear little relation to Windelband’s or Allport’s meaning. It seems that the concept has become untethered from its philosophical moorings and can mean almost anything that can be contrasted with standard (i.e. Galtonian) quantitative method. A few examples illustrate the diversity of uses. Lutz-Zois, Bradley, Mihalik & Moorman-Eavers (2006), in their paper “Perceived similarity and relationship success among dating couples: An idiographic approach”, use a standard large-N quantitative design, but justify their use of the term idiographic as they are concerned with variables that moderate the relationship between perceived similarity and positive relationship experiences. In contrast, for Rottenberg, Joorman, Brozovich & Gotlib (2005) and Barton et al. (2005) ‘idiographic’ data is that which is gathered using an open-ended data source, such as interview data or sentence-completion data. Eatough and Smith (2006) use the term idiographic to refer to a qualitative study that gains detailed data about the experience of anger for one person and explores individualised meanings of that emotion (in line with Allport’s definition). Hammond and O’Rourke (2007) refer to quantitative assessment tools of change as idiographic instruments. Barlow and Nock (2009) equate idiographic research with single-case experimental design, while Molenaar (2004) equates it with the analysis of intra-individual variability.

The basic problem is that idiographic research is not in fact premised on a specific method. Idiographic is an objective – the objective to describe or explain an individual thing. Psychologists tend to assume that natural sciences don’t engage in

1 Later in his career Eysenck promoted the importance of the single case in testing theory (Eysenck, 1976), and lamented the split between case-based research and group-based research. However, this interest in single-case research was based on a growing appreciation of the Wundtian paradigm, not on idiographic logic.

36 Oliver C. Robinson

this kind of activity, but they most certainly do. Every planet and moon in the solar system has been laboriously charted and mapped – an idiographic pursuit. And when the collapse of the twin towers occurred during 9/11, scientists endeavoured to explain how this could have happened – an idiographic pursuit. Science is not just the development and testing of theory, it is also the endeavour to describe and explain objects and events. Events, by definition, only happen once, and objects, by definition, are singular. Could the Wundtian paradigm fix the problem? Psychology has spent sixty or so years hobbling along on one leg, but it seems that most psychologists are unaware of this fact. The two legs of nomothetic psychology are the Wundtian case-by-case approach and the Galtonian aggregate approach, and Psychology had both of these legs intact until the 1930s. However Psychology has operated almost exclusively using the Galtonian approach since the 1940s, hence the hobble.

The loss of the Wundtian paradigm has meant that Psychology has had no widely accepted empirical basis for developing or testing fundamental, non-probabilistic theory for many decades. However this has not deterred mavericks. A rare and superb modern example of the Wundtian paradigm is Newell and Simon’s research on problem-solving. If you are wondering how Wundtian research actually looks in practice, get hold of a copy of their magnum opus Human Problem-Solving (Newell & Simon, 1972). Typical of Wundtian research, the theory put forward is true of all kinds of problem (i.e. single-solution puzzles) that it purports to cover. There are no statistics in the book, despite a fair amount of quantification, as they do not make probabilistic claims so there is no need for them. The book is also full of individual cases, some of which occupy an entire chapter. Why so? Because in the Wundtian paradigm, every case matters.

If Psychology can re-adopt this approach more widely, then it will find itself with a more complete conception of nomothetic science, and much-needed bridge between idiographic and nomothetic schemes. This will surely help to rectify the contemporary confusions that abound in this area. References Allport, G. W. (1937). Personality: A psychological interpretation. New York: Henry Holt. Allport, G.W. (1961). Pattern and growth in personality. London: Holt, Rinehart and Winston. Allport, G.W. (1962). The general and the unique in psychological science. Journal of Personality, 30, 405-422. Alzheimer A. (1911). Über eigenartige Krankheitsfälle des späteren Alters. Zeitschrift fűr die gesamte Neurologie und Psychiatrie, 4, 356-385. Bakan, D. (1967). On method: Toward a reconstruction of psychological

investigation. San Francisco: Jossey-Bass. Barlow, D.H. & Hersen, M. (1984). Single case experimental designs: Strategies for studying behavior change, Second edition. New York: Allyn & Bacon. Barlow, D.H., & Nock, M.K. (2009). Why can’t we be more idiographic in our research? Perspectives on Psychological Science, 4 (1), 19-21.

The Idiographic / Nomothetic Dichotomy 37

Barton, S., Morley, S., Bloxham, G., Kitson, C. & Platts, S. (2005). Sentence completion test for depression (SCD): An idiographic measure of depressive thinking. British Journal of Clinical Psychology, 44, 29–46

Beck, S.J. (1953). The science of personality: Nomothetic or idiographic? The Psychological Review, 60, 353-359. Cattell, J.M. (1886). The time taken up by cerebral operations. Mind, 11, 220-242. Danziger, K. (1990). Constructing the subject. Historical origins of psychological research. Cambridge University Press. Du Mas, F.M. (1955). Science and the single case. Psychological Reports, 1, 65-72. Eatough, V., & Smith, J.A. (2006). I feel like a scrambled egg in my head: An

idiographic case study of meaning making and anger using interpretative phenomenological analysis. Psychology and Psychotherapy: Theory, Research and Practice, 79, 115–135.

Ebbinghaus, H. (1885/1913). Memory: A contribution to experimental psychology (Translated by Ruger & Clara E. Bussenius). Originally published in New York by Teachers College, Columbia University.

Eysenck, H.J. (1954). The science of personality: Nomothetic! Psychological Review, 61, 339-342. Eysenck, H.J. (1976). Introduction. In H.J. Eysenck (Ed.), Case Studies in

Behavioural Therapy (pp.1-15). London: Routledge and Kegan Paul. Fisher, R.A. (1925). Statistical methods for research workers. Edinburgh: Oliver and

Boyd. Flyvbjerg, B. (2006). Five misunderstandings about case-study research. Qualitative Inquiry, 12, 219-245. Franck, I. (1982). Psychology as science: Resolving the idiographic-nomothetic controversy. Journal for the Theory of Social Behaviour, 12, 1–20. Freud, S. (1909). Analysis of a phobia in a five-year-old boy. In The Pelican Freud Library (1977), Vol 8, Case Histories 1, 169-306. Galton, F. (1889). Natural inheritance. London: Macmillan. Hammond, S., and O’Rourke, M. (2007). The measurement of individual change: A didactic account of an idiographic approach. Psychology, Crime and Law, 13,

81-95. Holt, R. (1962). Individuality and generalisability in the psychology of personality. Journal of Personality, 30, 377-404. Hurlburt, R.T. & Knapp, T.J. (2006). Münsterberg in 1898, not Allport in 1937, introduced the terms ‘idiographic’ and ‘nomothetic’ to American psychology. Theory & Psychology, 16, 2, 287-293. James, W. (1902/2002). The varieties of religious experience: A study in human

nature. New York: Dover Publications. Kazdin, A.E. (1982). Single-case research designs: Methods for clinical and applied

settings. Oxford: Oxford University Press. Kimble, G. (1984). Psychology's two cultures. American Psychologist, 39, 833-839. Kraepelin, E. (1895). Psychologische Arbeiten. Leipzig: Wm Engelmann. Lamiell, J.T. (1981). Toward an idiothetic psychology of personality. American Psychologist, 36, 276-289. Lamiell, J.T. (1998) ‘Nomothetic’ and ‘idiographic’ – contrasting Windelband’s understanding with contemporary usage. Theory & Psychology, 8, 1, 23-38. Lamiell, J.T. (2003). Beyond individual and group differences: Human individuality, scientific psychology, and William Stern’s critical personalism. London: Sage.

38 Oliver C. Robinson

Levine, F.M., Sandeen, E., & Murphy, C.M. (1992). The therapist’s dilemma: Using nomothetic information to answer idiographic questions. Psychotherapy, 29,

410-415. Lutz-Zois, C.L., Bradley, A.C., Mihalik, J.L., & Moorman-Eavers, E.R. (2006). Perceived similarity and relationship success among dating couples: An idiographic approach. Journal of Social and Personal Relationships, 23, 865–

880. Marinoff, L. (2003). The Big Questions. London: Bloomsbury. Molenaar, P.C.M. (2004). A manifesto on psychology as idiographic science:

Bringing the person back into scientific psychology, this time forever. Measurement: Interdisciplinary Research & Perspective, 2, 201-218.

Mook, D.G. (1983). In defense of external invalidity. American Psychologist, 38, 379-387. Münsterberg, H. (1899). Psychology and history. Psychological Review, 6, 1-31. Newell, A., & Simon, H.A. (1972). Human problem solving. Englewood Cliffs: Prentice Hall. Nunnally, J. C. (1978). Psychometric theory (2nd ed.). New York: McGraw-Hill. Pavlov, I.P. (1927). Conditioned reflexes: An investigation of the physiological

activity of the cerebral cortex. London: Oxford University Press. Piaget, J. (1923). Le langage et la pensée chez l'enfant. Paris: Delachaux et Niestlé. Pearson, K. (1896). Regression, heredity and panmixia. Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical

or Physical Character, 187, 253-318. Popper, K.R. (1972). Conjectures and refutations: The growth of scientific knowledge.

London: Routledge and Kegan Paul. Rottenberg, J., Joorman, J., Brozovich, F., & Gotlib, I.H. (2005). Emotional intensity

of idiographic sad memories in depression predicts symptom levels 1 year later. Emotion, 5, 238-242.

Shapiro, M.B. (1966). The single case in clinical-psychological research. The Journal of General Psychology, 74, 3-23. Skinner, B.F. (1953). Science and human behaviour. New York: MacMillan. Spearman, C. (1904). General intelligence objectively determined and measured.

American Journal of Psychology, 15, 201-293. Thorndike, E.L. (1911). Animal intelligence. Thoemmes Continuum. Titchener, E. B. (1905). Experimental psychology, a manual of laboratory practice: Volume II, Quantitative experiments, Part 1. Student’s manual. New York:

MacMillan. Tufts, J.H. (1895). Review of ‘History and natural science’. Psychological Review,

2(1), 96-97. Watson, J.B., and Rayner, R. (1920). Conditioned emotional reactions. Journal of Experimental Psychology, 3(1), 1-14. Windelband, W. & Oakes, G. (1894/1980). History and natural science. History and

Theory, 19(2),165-168. Windelband, W. (1901/2001). A History of Philosophy. New Jersey: Paper Tiger.

The Idiographic / Nomothetic Dichotomy 39

Address for correspondence Department of Psychology and Counselling, University of Greenwich, Avery Hill Road, London, SE9 2UG, UK Email: o.c.robinson@gre.ac.uk