Abstract: Q methodology was developed in the 1930s and has become increasingly utilized as a means for examining subjective behavior in a rigorous and naturalistic way. One of the advantages of Q methodology is its utility in examining single cases, which, when conjoined with the mathematics of factor analysis, reveals parallels with quantum theory. An illustration is presented from a study of national identity in which spontaneous and indeterminant expressions of national sentiment are selected from interviews and gathered into a Q sample which is then administered as a Q sort to a small group of participants. Factor analysis of the data reveals identities expressed as national pride, shame, and apprehension. A second study on authoritarianism illustrates the presence of quantum effects revealed in the subjective communicability of a representative personality to which the same Q sort is administered under multiple conditions of instruction, which demonstrates diverse response functions emerging as equivalent to the interference effects of quantum experiments.
 
 

It has now been more than 20 years since Montrose Wolf (1978) tried to show behavior analysts how to achieve greater social relevance by introducing the idea of social validity, which consisted of bringing social values into the scientific fold by assessing reinforcers in ways that society could understand and to which it could relate. The slippery concept of empathy, for example, was no longer to be disdained or replaced by a system of artificial reinforcers, but shown to be coterminous with maintaining eye contact, leaning forward, minimizing physical distance from the client, emitting "empathic" verbalizations, and other objective behaviors. One worked example consisted of students assigning grades of A through F to parent-teacher interactions such as voice tone, fairness, blaming, expressing concern, shouting, showing enthusiasm, and other socially-relevant dimensions, which were then averaged across students for each teacher, thereby vouchsafing that assessments were based on actual behaviors and appraised in terms with which the appraisers were familiar. Among the problems with subjective measurement which Wolf acknowledged was that they could be misleading: "Subjective data may not have any relationship to actual events" (Wolf, 1978, p. 212). Individuals are notoriously inaccurate about their behaviors and reinforcing consequences, and so among the suggestions made were to develop better measurement systems and to teach people more accurate ways of observing their behavior, all the while continuing to avoid any hint of "internal causal variables" (p. 213).

Protopostulatory to Wolf’s position is that subjective data can distort "actual events" (hence his stress on validity), and Skinner (1953) would agree: "... we may make a report which is in direct conflict with objective observations; we may report as unpleasant a type of event which can be shown to be reinforcing" (p. 82). Wolf and Skinner are interested in factual matters of this kind (i.e., in determining whether something is or is not, in fact, reinforcing), and this no doubt contributes to their relative disinterest in subjectivity as a naturally occurring phenomenon. However, a more general science of behavior cannot arbitrarily restrict itself to the assessment of true assertions: Lies, deceptions, and untestable statements may also be lawful, and in any event are the life-blood of a culture.

Among the behavioral postulates of Q methodology (Stephenson, 1953) is that a person’s subjectivity as such constitutes an actual event which exists in its own right and is measurable in its own terms with as much accuracy as measurements of a therapist’s body inclination or eye contact. A subjective behavior analysis in this sense finds few benefits from a concept like validity: A person’s opinion about something is simply that person’s opinion, and inquiring whether it is valid vis-à-vis "actual events" is a separate matter which overlooks the brute fact and eventful character of the opinion itself. Moreover, a subjective behavior analysis also finds little need for categorical averaging of the kind referred to uncritically by Wolf, relying instead on functional groupings in keeping with principles of specificity advanced by Kantor (1945) and Skinner (1953).¹  Finally, Q methodology stands shoulder to shoulder with most other forms of behavior analysis in consigning "internal causal variables" to the dustbin, but it is careful to retain the concept of subjectivity in recognition of the fact that "my opinion is my opinion," that "my thoughts are mine" (not someone else’s), which is scientifically acceptable as long as provision is made for suitable operations. As Stephenson (1953) said, "... the term behavior has to be such as to encompass all operations, from any frame of reference, whether ‘inner’ or ‘outer’" (p. 112).

Wolf can scarcely be blamed for his reticence about subjectivity,² which has an interbehavioral history that includes a variety of stimulus functions which behavior analysis endeavors to avoid, the most prominent being connotations related to consciousness. Jager (1998), for instance, equates the two, as does Hobson (1999): "... it is subjective conscious experience that we seek to explain" (p. 3). Ord (1998) associates subjectivity with emotion, while for Rosaldo (1994) it connotes the opposite of detachment; others implicitly refer to it as a substantive entity or internal process that can be initiated, fostered, or terminated at will, like the flow of water through a faucet (Sarbit, 1996). In their inventory of senses of subjectivity, Sabini and Silver (1982) identified only one—the subjectivity of point of view, as arises from different or shared vantagepoints—that was free of mental entanglements. For his part, Stephenson was insistent that consciousness and related mentalism were to be discarded, but that subjectivity was to be retained for scientific regard (Stephenson, 1968).

Apart from conceptual matters, there is also a methodological side to subjective behavior analysis. Whereas many behaviorists "solved" the public/private problem by restricting science to the former only, Skinner (1953) was more circumspect in recognizing that the dividing line is not permanent and that "the boundary shifts with every discovery of a technique for making private events public" (p. 282). So far as is known, Skinner was unaware of Q technique and its methodology,³ which was developed almost 20 years previously and which has solved many of the problems which Skinner and Wolf enumerated. Q methodology places the study of subjectivity on a scientific footing for the first time. An evolutionary development of the Spearman School of factor theory in the 1920s and ‘30s, it has the principle of operantcy at its roots and explicitly adopts major features of Kantor’s interbehaviorism (Brown, in press; Hayes & Fredericks, 1999, p. 92; Stephenson, 1984). In addition, as became more evident in Stephenson’s later writings, there is a surprising parallel between the concepts and mathematics of Q and quantum mechanics (Stephenson, 1982), including the most recent developments in superstring theory—all of which will gain clarity in the context of concrete examples.
 
 

A necessary distinction is made between facts (information) and opinion (communication) (Stephenson, 1969), the latter being subjective and requiring self-reference, the former objective and without self-reference: Hence, "I am an American" is a matter of fact (or not) and provable or falsifiable by anyone in terms of birth records, passports, court documents, and such. In contrast, the assertion that "America is the best country in the world" is not subject to proof, and is therefore referential to the person who expresses it; i.e., it has value or meaning within the person’s frame of reference. In this regard, subjectivity can be seen as ubiquitous and as covering everything from the quiet musings of an undergraduate pondering the possible interpretations of a poem to physicists contemplating the implications of the most recent readings from a particle accelerator, from the political discussions between friends over coffee to the flatulent puffery of the pundits, from the communicability of children to the reflections of old age.

Illustrative of subjective communicability are the following comments freely rendered during the course of a brief interview in response to the focalizing prompt, "What thoughts and feelings arise when you hear ‘I am an American’?":

I think of yellow ribbons and red, white, and blue.... I think of all the freedoms we have, democracy, voting—all the things we’re taught in school.... I don’t have really deep feelings.... I obey laws and vote, but I don’t feel patriotic.... I don’t think I would participate in a war.... We’re privileged in a material sense.... We’re a lot better off, and I like that.... I wouldn’t trade places with anyone else.... I wish others could be as well off as we are.... I don’t feel haughty or arrogant.... There are lots of things I’m not proud of.... I’m not emotional about it, but I prefer this to alternatives.... The depth of my feeling surprises me.... I’m not proud of the homeless, the status of minorities, the poor.... The legal system doesn’t always work....

And so forth in boundless supply. The interview from which the above fragments were extracted was one of several taken in 1991, in the wake of Operation Desert Storm (the Gulf War), which accounts for the references to war and patriotism. Skinner and Wolf would presumably point to the assertion that "I don’t have really deep feelings" as the kind of proposition of unknown connection to the true facts of the matter that would justify its disregard pending advances in assessment technology, but a subjective behavior analysis can at least proceed with measurements while others ponder veracity.

A collection of subjective communicability such as the above, when gathered from many interviews, is referred to as a concourse (Stephenson, 1978, 1980), from which a Q sample is eventually selected for purposes of experimentation. The individual elements of the Q sample (N=40 in this instance) are then typed on cards which participants Q sort by ranking them from agree (+4) to disagree (-4)Reference Erikson, and possibly: Seligman, S., & Shanok, R.S. (1995). Subjectivity, complexity, and the social world: Erikson’s identity concept and contemporary relational theories. Psychoanalytic Dialogues, 5, 537-565., usually in a quasi-normal or other arbitrarily-shaped distribution. Once provided, the responses (n=28 in this illustration) are then correlated (resulting in a 28×28 matrix) and factor analyzed (Schmolck & Atkinson, 1998), with factors in Q methodology indicating the different ways in which the participants sorted the statements. Factor scores are then estimated for the statements in each factor so as to facilitate comparisons and contrasts. Technical details are unnecessary at this point and can be found elsewhere (Brown, 1980, 1993).

In this particular experiment, more than two dozen individuals responded, and this resulted in three factors. As might be expected, one of them (Factor A) represented an idealization of America, as is readily apparent in those statements which received higher scores in this factor than in the other two (the three scores to the left of each statement are for Factors A to C, respectively):

                                                            0 4 1 (e) I’m ashamed that we are not doing enough to try and solve
                                                                         social problems.

In this regard, it is worth considering what factors such as the above could mean for a more general behavior analysis, one that would feel as scientifically comfortable examining national identity as it would assessing the eye contact and body movements of psychotherapists.

The term quantum has achieved a certain popularity such that it has been drawn upon as an analogy in literature, art, mysticism, and the social sciences, but it is primarily about measurement, and it is in terms of measurement that it is in remarkable parallel with Q methodology. Stephenson was fully cognizant of this. Trained originally as a physicist (PhD 1926, University of Durham) during the time in which the Copenhagen Interpretation was gaining the upper hand, and only later as a psychologist (PhD 1929, University of London), he was aware from the outset about the mathematical similarities between quantum mechanics and factor analysis,⁴ and it is due to its reliance on measurement that Q is able to escape being just another "striking analogy." The similarities extend into superstring theory and developments subsequent to Stephenson’s death (for example, see Davies & Brown, 1993; Greene, 1999; Gribbin, 1998a, 1998b).

Apart from the mathematics involved, some of the more striking similarities are as follows, and are more fully treated in Stephenson’s later writings (Stephenson, 1982, 1983, 1986a, 1986b, 1987, 1988a, 1988b, 1989):

Thoughts, like birds, sometimes flit and sometimes perch, as William James (1890, p. 243) said: The latter he called substantive, the former transitive. Q methodology deals mainly with transitive thought, an example of which is given in the interview fragment on p. 4 (supra). Behavior of this kind is indeterminant inasmuch as we can never predict in advance what the person will say next: Even the person rarely knows. In the silence prior to an utterance, virtually anything could be said, but as in the collapse of the wave packet in quantum theory, at the moment of utterance all potentiality vanishes and one thought assumes a probability of 1.00. Transitive thought also has gaps, as when the person says that "I think of all the freedoms we have, democracy, voting—all the things we’re taught in school ... [gap] ... I don’t have really deep feelings." When one thought is being expressed, others are precluded, in the same way that light can display its wave features or particle features, but not both at the same time.

Similarly, the statements in a Q sample initially have a low level of meaning (comparable to the ground state of energy) and are subsequently endowed with excessive meaning and significance in the course of Q sorting. It is in this sense that statements of a concourse are considered to be "equipotential and equipossible a priori" (Stephenson, 1980, p. 9). Although a statement might mean many things in the abstract, it is eventually endowed with a specific meaning (collapse of the wave packet) and receives a score.

In the same way that measurement is inextricably involved in what is observed in quantum theory, so it is in Q methodology that the person whose perspective is under observation is also the person providing the Q-sort measure of that perspective; i.e., the "observer" is not the scientist, but the participant, who is observing his or her own point of view while providing a measure of it.

When a Q sort is performed multiple times by the same person under different conditions, the factors which emerge indicate natural segregations in the person’s mind, and it is at this point that Q methodology and quantum theory coincide:
 

Quantum theory in physics begins with a Hilbert-space vector and provides a probability distribution; in Q the same holds. The Q-sorter projects probability distributions upon an otherwise undifferentiated concourse. It is achieved because of lawful conditions..., imposed upon situations by the conditions of instruction for Q-sorts, comparable to the projections of vectors upon the eigenvektorens of operators in quantum theory. (Stephenson, 1982, p. 238)
 

As with superstring theory, the indivisible unit of Q methodology is the person’s point of view, represented not as a single point object (like a score on a variable), but as an elongated dimension (ranging from +4 to -4, for instance) that forms a pattern. The Q sort represents a state of mind (comparable to an energy state in quantum theory) rather than a variable in a state, as is the case in R methodology.⁵
 
 

In elaborating upon string theory, Greene (1999) states that "one way that we learn about the structure of an object is by hurling other things at it and observing the precise way in which they are deflected" (p. 152), and in Rich’s case, the various conditions of instruction hurled at him were deflected in three ways (Factors A, B, and C), each representing a different side to his character. His Factor A reveals what psychoanalysis would refer to as a substantial internalization of the parents (i.e., the fact that Rich’s description of himself is on the same factor with his description of how his mother and father view him), which is the kind of conformity that theory would lead us to expect of an authoritarian personality. That Rich’s favorite teacher and President Kennedy would view him in essentially the same way would be indicative of projection. Factor B represents Rich’s peer group, and it is likely this dimension of his social existence that gave rise to the sexually-liberated and non-traditional views in evidence previously. Factor C represents organic collectivities that transcend the self and to which the self voluntarily relinquishes its sovereignty for the sake of group goals and achievements. As in quantum theory, Rich’s factors are in a relationship of complementarity, not by assertion or definition, but as a consequence of measurement: He sometimes conducts himself like Factor A, sometimes like B, sometimes like C.

The quantum-mechanical equivalent of interference effects is revealed in those factor scores that display diverse response functions (scores to the left for Factors A, B, and C, respectively):
 

Table 1 Rich’s Operant Factors Condition	A	B	C
self	(81)	-14	-01
father	(53)	-34	(58)
mother	(80)	-07	30
favorite teacher	(50)	-33	39
President Kennedy	(56)	41	-19
self in 20 years	(55)	18	-24
buddies	19	(55)	00
female friends	22	(80)	-13
football team	-06	02	(56)
priest	32	-16	(57)

Factor loadings in parentheses significant, p<.01; decimals to two places omitted.
 

3 0 -1 (a) You’ve got to have tradition in the family: it helps establish who you are.

0 2 -3 (b) I don’t think premarital sex is a crime or anything. No one’s actually getting hurt.

1 -2 3 (c) I think that we should try to keep some of the old rules—they help keep us in line.

2 3 3 (d) I never really neglected an obligation to my family.

In particle physics, interference effects refer to "the way in which ... waves interact with one another to produce an overall pattern ... of high intensity and low intensity" (Gribbin, 1998b, p. 185), as in the clash of waves of boats moving in opposite directions. In this regard, we note that statement (a) above receives the highest score (+3) with regard to Factor A (parental), but that the momentum of this sentiment does not carry over into Factors B (peers) or C (church, team). Similarly, statement (b) emerges to prominence in the interpersonal field dominated by the reference group, and (c) is given preference in the church/team context. Statement (d) is not subject to interference effects, and maintains essentially the same salience regardless of the situation.
 
 
 

Concluding Remarks

Space precludes presentation of myriad other experiments which would provide details concerning Q methodology’s remarkable parallel with quantum theory. Suffice it to say that they point in a more realist direction—i.e., that "there is a real world, and it jumps!" as Stephenson once remarked only partly in jest—rather than in a direction that would implicate consciousness and mystical mind-matter connections, which are in surprising circulation even among physicists (e.g., Stapp, 1993). The brain is composed of atoms and subatomic particles, no doubt, but one needn’t descend into neurophysiology to find quantum effects: As the above examples show, such effects exist in the subjective communicability of everyday life. Moreover, they display lawfulness—as in the obvious fact (in Table 1) that Factor A contain Rich’s self (hence is me) whereas Factors B and C represent others’ views of him (hence are mine, but not me) (James’ Law); that each of the factors is schematical (Peirce’s Law of Mind); that Factor A implicates time (Rich now and in 20 years), hence the possibility of change (Parloff’s Law); and others. It is therefore unnecessary for Skinner and Wolf to assume a polite reserve with respect to subjectivity as a psychological event, since with Q methodology such behaviors can be examined quite naturalistically with all the rigor and experimental care that attends the study of mice and pigeons.
 
 

1. Well before Kantor and Skinner, Bernard (1865/1927) remarked that “we must never make average
descriptions of experiments, because the true relations of phenomena disappear in the average” (p. 135);
and as Zizek (1913) later observed, “If masses of items ... are taken together in a series the average so
computed has little scientific value, since it does not express the activity of a unified complex of natural or
social causes...” (p. 65).

2. Wolf’s reticence was shared by J.R. Kantor, who, in a brief correspondence, once remarked that “it is very
difficult for me to deal with subjectivity, although no doubt you only mean by that term individual or
personality” (personal communication, March 11, 1983).

3. Stephenson, on the other hand, was fully cognizant of Skinner’s main contributions, and was instrumental
in arranging for Skinner to receive an honorary doctorate at the University of Missouri in 1968. It was at
this time that Stephenson wrote his paper on “Factors as Operant Subjectivity” (1969/1977) which inspired
the journal Operant Subjectivity (currently in its twenty-second volume) as the main outlet for Q-methodological
scholarship.

4. I once invited to a graduate seminar a theoretical physicist and a factor analyst, the latter having been trained at
Princeton’s Educational Testing Service, and in the course of the discussion, during which each tried to explain to
the other how he went about doing his work (as physicist or psychometrician), the two of them eventually began to
discover that they were using essentially the same matrix mechanics to solve their respective problems, the only
difference being that the physicist inserted unity into the main diagonal whereas the psychologist inserted multiple
R. For accessible introductions, see Gribbin (1998b, pp. 224-228), Hammer (1971), and Peat (1990, pp. 35-40);
more advanced treatments are in Lyons (1986) and Malinowski and Howery (1980).

5. Quantum theory does not refer to any individual particle, but to the energy state of an entire system. Conventional
social and psychological measurement, by way of contrast, measures individual variables (the rule of the single
variable). Quantum theory therefore cannot apply in R methodology other than as an analogy.
 
 

Altemeyer, B. (1981). Right-wing authoritarianism. Winnipeg: University of Manitoba Press.

Bentley, A.F. (1908). The process of government. Chicago: University of Chicago Press.

Bernard, C. (1927). An introduction to the study of experimental medicine (H.C. Green, Trans.). New York: Macmillan. (Original work published 1865)

Born, M. (1927). Physical aspects of quantum mechanics. Nature, 119, 354-357.

Brown, C., & Parsons, P. (1998, November). Perspectives on the problem of homework: A Q-methodological study of sixth grade students. Paper presented at the meeting of the International Society for the Scientific Study of Subjectivity, Seoul, Korea.

Brown, S.R. (1980). Political subjectivity: Applications of Q methodology in political science. New Haven, CT: Yale University Press.

Brown, S.R. (1985). Comments on "The Search for Structure." Political Methodology, 11, 109-117.

Brown, S.R. (1993). A primer on Q methodology. Operant Subjectivity, 16, 91-138.

Brown, S.R. (in press). Q methodology and naturalistic subjectivity. In B.D. Midgley & E.K. Morris (Eds.), Modern perspectives on J.R. Kantor and interbehaviorism. Westport, CT: Greenwood. Brown, S.R., Durning, D.W., & Selden, S.C. (1999). Q methodology. In G.J. Miller & M.L. Whicker (Eds.), Handbook of research methods in public administration (pp. 599-637). New York: Marcel Dekker.

Davies, P.C.W., & Brown, J. (Eds.) (1988). Superstrings: A theory of everything? Cambridge, UK: Cambridge University Press.

Devlin, K. (1998). The language of mathematics: Making the invisible visible. New York: Freeman.

Gargan, J.J., & Brown, S.R. (1993). "What is to be done?" Anticipating the future and mobilizing prudence. Policy Sciences, 26, 347-359.

Greene, B. (1999). The elegant universe: Superstrings, hidden dimensions, and the quest for the ultimate theory. New York: Norton.

Gribbin, J. (1998a). The search for superstrings, symmetry, and the theory of everything. Boston: Little, Brown

Gribbin, J. (1998b). Q is for quantum: An encyclopedia of particle physics. New York: Free Press.

Hammer, A.G. (1971). Elementary matrix algebra for psychologists and social scientists. Rushcutters Bay, NSW, Australia: Pergamon Press.

Hayes, L.J., & Fredericks, D.W. (1999). Interbehaviorism and interbehavioral psychology. In W.O’Donohue & R. Kitchener (Eds.), Handbook of behaviorism (pp. 71-96). San Diego: Academic Press.

Hobson, J.A. (1999). Consciousness. New York: Scientific American Library.

Jager, B. (1998). Human subjectivity and the law of the threshold: Phenomenological and humanistic perspectives. In R. Valle (Ed.), Phenomenological inquiry in psychology: Existential and transpersonal dimensions (pp. 87-108). New York: Plenum.

James, W. (1890). The principles of psychology. New York: Henry Holt.

Kantor, J.R. (1945). Psychology and logic (Vol. 1). Bloomington, IN: Principia Press.

Kantor, J.R. (1959). Interbehavioral psychology (2^nd ed.). Granville, OH: Principia Press.

Kantor, J.R. (1966). Feelings and emotions as scientific events. Psychological Record, 16, 377-404.

Kantor, J.R. (1984). The relation of scientists to events in physics and in psychology. Psychological Record, 34, 165-173.

Lyons, L. (1986). Statistics for nuclear and particle physicists. Cambridge, UK: Cambridge University Press.

Malinowski, E.R., & Howery, D.G. (1980). Factor analysis in chemistry. New York: Wiley.

Maxwell, J., & Brown, S.R. (1997, October). Identifying problems and generating solutions under conditions of conflict. Paper read at the meeting of the International Society for the Scientific Study of Subjectivity, Syracuse University, Syracuse, NY.

Ord, J. (1998). Subjective experience and social enquiry. In P. Griffiths, J. Ord, D. Wells, & E. Barnes (Eds.), Face to face with distress: The professional use of self in psychosocial care (pp. 42-52). Oxford, UK: Butterworth-Heinemann.

Peat, F.D. (1990). Einstein’s moon: Bell’s Theorem and the curious quest for quantum reality. Chicago: Contemporary.

Rhoads, J.C., Jr. (1998). The authoritarian personality revisited: Toward an alternative methodology (Doctoral dissertation, Kent State University, 1997). Dissertation Abstracts International, 58, 4431 Rosaldo, R. (1994). Subjectivity in social analysis. In S. Seidman (Ed.), The postmodern turn: New perspectives on social theory (pp. 171-183). Cambridge, UK: Cambridge University Press.

Sabini, J.B., & Silver, M. (1982). Some senses of subjective. In P.F. Secord (Ed.), Explaining human behavior: Consciousness, human action and social structure (pp. 71-91). Beverly Hills, CA: Sage.

Sarbit, B. (1996). James Bugental: Champion of subjectivity. Journal of Humanistic Psychology, 36(4), 19-30.

Schmolck, P., & Atkinson, J. (1998). PQMethod (Version 2.06) [Computer software]. Available

Skinner, B.F. (1953). Science and human behavior. New York: Macmillan.

Skinner, B.F. (1969). Contingencies of reinforcement. New York: Appleton-Century-Crofts.

Stapp, H.P. (1993). Mind, matter, and quantum mechanics. Berlin: Springer-Verlag.

Stephenson, W. (1953). Postulates of behaviorism. Philosophy of Science, 20, 110-120.

Stephenson, W. (1967). The play theory of mass communication. Chicago: University of Chicago Press.

Stephenson, W. (1968). Consciousness out—subjectivity in. Psychological Record, 18, 499-501.

Stephenson, W. (1969). Foundations of communication theory. Psychological Record, 19, 65-82.

Stephenson, W. (1977). Factors as operant subjectivity. Operant Subjectivity, 1, 3-16. (Original work published 1969).

Stephenson, W. (1978). Concourse theory of communication. Communication, 3, 21-40.

Stephenson, W. (1980). Consciring: A general theory for subjective communicability. In D. Nimmo (Ed.), Communication Yearbook 4 (pp. 7-36). New Brunswick, NJ: Transaction.

Stephenson, W. (1982). Q-methodology, interbehavioral psychology, and quantum theory. Psychological Record, 32, 235-248.

Stephenson, W. (1983). Quantum theory and Q-methodology: Fictionalistic and probabilistic theories conjoined. Psychological Record, 33, 213-230.

Stephenson, W. (1984). Methodology for statements of problems: Kantor and Spearman conjoined. Psychological Record, 34, 575-588.

Stephenson, W. (1986a). William James, Niels Bohr, and complementarity: I—Concepts. Psychological Record, 36, 519-527.

Stephenson, W. (1986b). William James, Niels Bohr, and complementarity: II—Pragmatics of a thought. Psychological Record, 36, 529-543.

Stephenson, W. (1987). William James, Niels Bohr, and complementarity: III—Schrödinger’s cat. Psychological Record, 37, 523-544.

Stephenson, W. (1988a). William James, Niels Bohr, and complementarity: IV—The significance of time. Psychological Record, 38, 519-527.

Stephenson, W. (1988b). William James, Niels Bohr, and complementarity: V—Phenomenology of subjectivity. Psychological Record, 38, 203-219.

Stephenson, W. (1989). Quantum theory of subjectivity. Integrative Psychiatry, 6, 180-187.

Thomas, D.B., & Baas, L.R. (1992-1993). The issue of generalization in Q methodology: "Reliable schematics" revisited. Operant Subjectivity, 16, 18-36.

Wolf, M.M. (1978). Social validity: The case for subjective measurement, or How applied behavior analysis is finding its heart. Journal of Applied Behavior Analysis, 11, 203-214.

Zizek, F. (1913). Statistical averages: A methodological study (W.M. Persons, Trans.). New York: Henry Holt.