Personality psychology is the academic sub discipline of psychology that focuses on the description, measurement, environmental and physiological bases, developmental history and life course and the consequences of individual differences in adaptation to ones’ environment. As a field of study, it is perhaps the last refuge of the generalist in psychology, for the personality psychologist integrates research methodology, particularly that of measurement, with the study of the genetic and physiological bases of behavior, with the study of social and cultural determinants of behavior, as well as the normal and pathological. The study of personality includes the evolutionary causes that make us all the same, it is also the study of individual differences that describes how we differ from each other is systematic ways, and it is the study of human uniqueness, how each of us organizes our life in a unique way.
The study of individual differences includes the study of affect, behavior, cognition, and motivation as they are affected by biological causes and environmental events. That is, it includes all of psychology. But it is also the study of individual differences that are not normally taught in psychology departments. Human factors, differences in physical abilities as diverse as taste, smell, or strength are also part of the study of differential psychology. Differential psychology requires a general knowledge of all of psychology for people (as well as chimpanzees, dogs, rats and fishes) differ in many ways. Thus, differential psychologists do not say that they are cognitive-psychologists, social-psychologists, neuro-psychologists, behavior geneticists, psychometricians or methodologists, for although we do those various hyphenated parts of psychology, by saying we study differential psychology, we have said we do all of those things. And that is true for all personality psychologists. We study differential psychology. Individual differences in how we think, individual differences in how we feel, individual differences in what we want and what we need, individual differences in what we do. We study how people differ and we also study why people differ. We study individual differences.
Personality is the coherent patterning over time and space of an organism’s affective, cognitive and motivational state as they lead to behavior. The emphasis is two fold: on the coherence of the patterning (that is to say, it is more than random noise), and that the patterning is over time and space, that is to say, it is the description of a dynamic system.
As my colleagues and I have said before (Revelle et al., 2011) the coherent patterning of affect, behavior, cognition, and desire may be understood at three levels of information processing - reactive, routine, and reflective (Ortony et al., 2005). It is important to note that the reactive, routine, and reflective levels are not separated by sharp boundaries but lie on a continuum of complexity ranging from more basic and immediate processes (reactive) to well-learned and rehearsed processes (routine) to complex and abstract processes (reflective).
The reactive level of information processing comprises rapid and efficient responses to stimuli. Responses at this level consist of a unified combination of affective and behavioral and motivational processes. For example, after touching a stove burner, the motivation to avoid pain, (Desire), fear (Affect), and removal of one’s hand (Behavior) likely occur simultaneously and do not require elaborated cognition. The routine level comprises well-learned, everyday activities. At this level, affect, behavior, and motivation may be distinguished from each other due to the emergence of low-level cognitive processes. At the routine level of processing, an individual noticing his or her hand approaching a hot stove would be able to cognitively discriminate between the present state of not being in pain and fear (Affect) an uwanted future state of pain (Desire). The individual may thus act (Behavior) to increase the likelihood that pain does not ensue. The reflective level describes higher-level cognitive functioning such as self-awareness and metaprocessing. At this level affect becomes enriched with cognitive content such that conscious plans may guide behavior toward or away from well-elaborated and nuanced goals. One may safeguard the stove so that young children are unlikely to come into contact with the burners.
The above examples lead to the realization that the ABCDs constantly interact in dynamic ways across multiple levels of information processing. As such, those dynamic interactions should be a focal point of differential psychology theories and failure to consider such dynamics may limit the generation of comprehensive theories of individual differences. By adopting an information-processing approach, the study of differential psychology becomes the study of the coherent patterning of ABCDs across time and space (Wilt & Revelle, 2009). The task of differential psychology thus becomes the task of explaining why people have different ABCD patterns across the different levels of information processing and determining how those differences relate to important outcomes.
Throughout my high school and college education, I thought I would go into oceanography. I had grown up with oceanographers and had spent three summers on oceanographic expeditions exploring the Pacific Ocean from San Diego to Thailand, from Samoa to Point Barrow. In college I was a mathematics major because this gave the most freedom to take courses in other fields including geology, physics, chemistry and music. Before my junior year in college, I spent the summer working at the computer center of the University of California, San Diego. This was to learn how to use computers to analyze the complex physical data on waves that oceanographers studied. This was an important experience for me in that I became even more interested in how computers process information and whether it was possible to teach computers to learn.
In order to study how computers learn, I thought it would be helpful to take a course in the psychology department on how animals and humans learn. Reading the works of Edward Tolman made be very interested in studying learning in psychology. Tolman integrated formal models of learning with general principles of psychology. Thus, in my senior year in college I switched to a psychology major. As part of that major I became very interested in social psychology and also studied the personality correlates of creativity among my junior and senior classmates.
My interest in personality as a sub field of psychology crystallized when I spent two years in the United States Peace Corps in Sarawak, Malaysia. The only books on personalty at the local (100 Km away) book store in Brunei were three paper backs by Hans Eysenck: Fact and Fiction in Psychology, Sense and Nonsense in Psychology, and Uses and Abuses of Psychology. Reading these three books hooked me on studying personality in graduate school for I realized one could apply mathematics to the study of human behavior. I did this at the University of Michigan where I took my Ph.D. working with John W. (Jack) Atlkinson, Theodore (Ted) Newcomb, Warren Norman, Dick Nisbett, Clyde Coombs, and under the very tolerant advice of my thesis advisor, Donald Brown.
I am currently working on several different projects that are interrelated. The first is the structure of personality. This is the question of how one’s affects, behaviors, cognitions and desires interrelate with each other to form what is commonly referred to as the Big 5 dimensions of personality. The Big 5 are, to me, merely a convenient way to describe how biological sensitivities to cues for rewards and punishments affect how we feel (our affect) and think (our cognitions) about the environment.
A second interest is the dynamics of affect and behavior measured within individuals. By tracking individuals over several week, and asking them to answer questions 5 -8 times a day about how they feel and what they are doing, my students and I are able to explore the within person structure of emotions. This within person structure differs between individuals.
Related to the study of affect within individuals is the development of a motivational theory to explain the complex dynamic patterns. Computer simulations (Revelle, 1986) implement in the R language in the psych package using the cat function can demonstrate the complex interplay of motives over time.
The third problem I am working on is the development of open source, public software for analyzing psychological data, with a particular interest in personality measurement. This has resulted in the psych package in the statistical computer system R.
I partly went into psychology and left computer science because I did not want to develop weapons that could be used in warfare. It seemed to me that computer science was likely to end up being used in war. I did not want to be involved in such a process. As a consequence, I went as far as I could from something that had military implications.
I have not had any serious challenges in my work. I have been fortunate to have very good colleagues and superb students, both graduate and undergraduate.
By working with excellent students, I have been able to pursue questions having to do with personality for the past 40 years. My vita suggests that I have been moderately successful in doing so.
By understanding the different ways in people respond to situations, and understanding their unique abilities, we are better able to help people achieve their potential. People do not respond to challenges the same way. Some see them as threats to be avoided, others view them as challenges to be overcome. By studying differences in approach and avoidance motivation, by studying differences in intellectual ability, we are better able to advice people to interact with their world.
I am most proud to the number of excellent graduate and undergraduate students that I have trained during my 40 years at Northwestern. They are now scholars all around the world. In addition, my 9 years as chairman of our Department of Psychology resulted in rebuilding our department and helping it become the excellent program that it is today.
My scholarly accomplishments include a theory of how personality interacts with situational stressors to affect complex cognitive performance (Humphreys & Revelle, 1984), experimental evidence for the interaction of personality traits, situational stressors, and time of day as they affect cognitive performance (Revelle et al., 1980), evidence for how extraversion relates to reinforcement cues to lead to positive affect (Smillie et al., 2012), and the within subject structure of emotion (Wilt et al., 2011). Methodological contributions have included developing an algorithm for hierarchical cluster analysis (Revelle, 1979), and a general statistical system for the analysis of psychological data (Revelle, 2012).
My various contributions have resulted in my being elected as president of three different organizations: the Society of Multivariate Experimental Psychology, the International Society for the Study of Individual Differences, and the Association for Research in Personality. I am a fellow to the American Association for the Advancement of Science, the Association of Psychological Science, and the American Psychological Association.
I have just finished four years as chairman of the governing board of the Bulletin of Atomic Scientists, an organization devoted to the preservation of mankind by the elimination of the existential threats of nuclear war, global climate change, and biological and cyber terrorism.
The more mathematics that one takes the better one can do in any field, particularly in personality research.
Humphreys, M. S., & Revelle, W. (1984). Personality, motivation, and performance: A theory of the relationship between individual differences and information processing. Psychological Review, 91(2), 153-184.
Ortony, A., Norman, D. A., & Revelle, W. (2005). Affect and proto-affect in effective functioning. In J. Fellous & M. Arbib (Eds.), Who needs emotions? The brain meets the machine. (p. 173-202). New York: Oxford Univeristy Press.
Revelle, W. (1979). Hierarchical cluster-analysis and the internal structure of tests. Multivariate Behavioral Research, 14(1), 57-74.
Revelle, W. (1986). Motivation and efficiency of cognitive performance. In D. R. Brown & J. Veroff (Eds.), Frontiers of motivational psychology: Essays in honor of J. W. Atkinson (p. 105-131). New York: Springer.
Revelle, W. (2012). psych: Procedures for personality and psychological research [Computer software manual]. Evanston. Retrieved from http://personality-project.org/r (R package version 1.2.8)
Revelle, W., Humphreys, M. S., Simon, L., & Gilliland, K. (1980). The interactive effect of personality, time of day and caffeine: A test of the arousal model. Journal of Experimental Psychology: General, 109, 1-31.
Revelle, W., Wilt, J., & Condon, D. (2011). Individual differences and differential psychology: A brief history and prospect. In T. Chamorro-Premuzic, A. Furnham, & S. von Stumm (Eds.), Handbook of individual differences (p. 3-38). Oxford: Wiley-Blackwell.
Smillie, L. D., Cooper, A., Wilt, J., & Revelle, W. (2012). Do extraverts get more bang for the buck? refining the affective-reactivity hypothesis of extraversion. Journal of Personality and Social Psychology, 103(2), 306-326. doi: 10.1037/a0028372
Wilt, J., Funkhouser, K., & Revelle, W. (2011). The dynamic relationships of affective synchrony to perceptions of situations. Journal of Research in Personality, 45, 309–321.
Wilt, J., & Revelle, W. (2009). Extraversion. In M. Leary & R. H. Hoyle (Eds.), Handbook of individual differences in social behavior (p. 27-45). New York, N.Y.: Guilford Press.