What is psychology? If you were asked to define it, could you? In the 12 years that I’ve been studying psychology, I’ve been asked no more than 5 times what psychology is, and each time, I struggled and ultimately failed to come up with a definition. To be honest, though, that doesn’t bother me in the least. If there’s one thing psychology has taught me, it’s that definitions aren’t worth a whole hell of a lot anyway. And given how few times the issue has come up, despite the fact that I’ve been surrounded by psychologists for the entirety of my adult life, I never really thought it bothered anyone else all that much either. Until I read this post at PsyBlog, that is. There I found links to a series of posts on “unity in psychology.” Those posts discuss what appears to be an ongoing debate about how to unify psychology, theoretically, methodologically, terminologically, etc., and central to that discussion is how to define psychology.

Now, I sympathize with some of the concerns that are raised in those posts and the articles they cite. Here are a few quotes to give you an idea of what motivates people to unify psychology:

Psychology has so many unrelated elements of knowledge with so much mutual discreditation, inconsistency, redundancy, and controversy that abstracting general meaning is a great problem. There is a crisis, moreover, because the disunification feeds on itself and, left unchanged, will continue to grow.1

It is simply a sad fact that in soft psychology theories rise and decline, come and go, more as a function of baffled boredom than anything else; and the enterprise shows a disturbing absence of that cumulative character that is so impressive in disciplines like astronomy, molecular biology and genetics.2

Psychology, meanwhile, languishes back in the Dark Ages compared to physics. At least physics has agreed on common terminology for its fundamental concepts. You don’t find different physicists with different names for gravity. By contrast in psychology, as Staats (1999) points out, we have, for example: ‘self-concept’, ‘self-image’, self-perception’, ‘self-esteem’, ‘self-efficacy’ and the plain old ‘self’. What’s the difference? Perhaps little, yet all these words are still used and this is just one of many ill-defined concepts. (From this post at PsyBlog)

When I started my first psychology course I couldn’t understand the separation between the different subjects, or disciplines, in psychology. Developmental psychologists aren’t that much different from cognitive psychologists – they both study mental events and processes – but one almost never refers to the other. Why? (From this post at PsyBlog)

It’s certainly true that, across the different areas of psychology, there is a great deal of redundancy and contradiction in psychological theories, and god knows the discipline has terminological problems. It’s not just that there are a bunch of terms for constructs that are basically the same, but the terms we use tend to be vague and confusing (just try to figure out what a schema is to a social psychologist). The field could definitely be served, then, by more inter-area communication, and an emphasis on terminological rigour. But a unified psychology?

First, what would a unified psychology be? To start, you need a definition. The clearest definition I found when reading the papers and posts at PsyBlog was in a paper by John Kihlstrom3. He wrote:

The unity of psychology as a science is to be found in its definition as the science of mental life, and its explanation of individual behavior in terms of mental states.

But no, that’s not true. I doubt the psychologists studying the nervous systems of flatworms (and there are biological psychologists who do that sort of thing, you know) would say that they’re studying mental life, or that they explain anything about flatworms in terms of mental states. It may just be a philosophical prejudice of mine, but I don’t think flatworms have mental states. Sure, you could argue that they’re studying mental life indirectly, by learning about neural processes which can be extended to species that do have mental states, and whose behaviors can be explained in terms of mental states, but that just feels like cheating. This definition, like all definitions, suffers from the problem that if you look hard enough (and in this case, I didn’t have to look very hard), you can find exceptions. So the project is off to a rocky start.

The next step in unifying psychology is to come up with some sort of unifying theory. A representative example of such an attempt comes from Gregg Henriques4. Henriques takes an epistemological approach to unification. He writes:

What is needed is a metatheoretical framework that crisply defines the subject matter of psychology, demonstrates how psychology exists in relationship to the other sciences, and allows one to systematically integrate the key insights from the major perspectives in a manner that results in cumulative knowledge. (p. 152)

For Henriques, that metatheoretical approach can be found at the midpoint between Skinnerian behaviorism, with its focus on observable behavior and rejection of all things mental, and Freudian psychoanalysis, with its focus on exactly what behaviorism rejects, the mental. This suggestion is mindbogglingly banal. Forgetting for a moment that Freudian psychoanalysis has a lot of baggage that we don’t want, this middle-ground is essentially what the cognitive revolution gave us (as Kihlstrom notes). Cognitive science is essentially behavioristic, particularly in its methodology, but it admits, and even focuses on, the mental. Since the cognitive revolution begain 50 years ago, and since that time psychology has developed several new areas, while terminological confusion has remained consistent, if it hasn’t increased, something tells me that this approach to unification ain’t gonna work.

As far as I can tell, then, this discussion is getting us nowhere. And it’s not likely to in the foreseeable future, either. The problem with it is pretty clear. As you can see from the above quotes, the ultimate motivation for unifying psychology is one that has both helped and hindered modern psychology since its inception in the 19th century: phsyics envy. These people want psychology to be like the natural sciences, and physics in particular. But the thing is, psychology isn’t physics. For one, physics has got a couple millenia on psychology (and even if you only consider modern physics, it’s still got a good 500 years on psychology). Hell, old man physics can’t agree on a single paradigm, so it would be a miracle if toddler psychology could. Furthermore, I’m not convinced that the reason there are different, competing paradigms, isn’t a good one. We understand so little about thought and behavior that there is a lot of room for disputes about how to go about thinking about them. In cognitive science, the connectionist, embodied cognition, dynamic systems theory, computationalism, exist, and compete (though there’s overlap and cooperation, too) because they each provide insights that the others lack. That’s to be expected in a young discipline, and I think it’s a good thing. It speeds the process of understanding and explanation along, because it allows people to take multiple perspectives on the problems with which we’re struggling.

That leads to the second reason why a unified psychology based, either analogically or literally, on the model of physics, is doomed to fail. Psychology is just more complex than phsyics. The brain is wider than the sky, and all that. The reason there are so many areas of psychology, and so many specialized sub-areas, is that there are all sorts of behaviors and mental processes (theoretically, an infinite number). Even if we do come up with a unified metatheoretical framework for studying them someday, we’re still going to have a bunch of different areas and sub-areas, because we’ll still have to study all of those different types of behaviors and mental processes. I probably don’t need to tell you this, but a bunch of areas and subareas within physics, too. I wonder how much communication there is between geophysicists and those people who hang out at particle accelorators. My guess is, about as much as there is between cognitive psychologists and and the people studying the development of antisocial behavior in adolescents.

None of this is to say that psychology couldn’t benefit from more communication between areas, as I said before. In grad school, I took a course on memory that was designed for clinical psychologists, and was amazed at how little the head-shrinkers-in-training knew about even the basics of memory, despite the fact that memory plays a central role in many psychological disorders. And we cognitive psychologists could probably benefit from spending more time with individual differences psychologists, because we tend to get wrapped up in the middle of distributions, and forget that their tails even exist. We don’t need a unified metatheoretical framework to talk to people whose labs are on different floors in the psychology building, though. We just need to be more social, and maybe to read some of those journals that we have on the bookshelves in our offices, but have never actually opened. I’m also inclined to believe that terminological confusion could be alleviated by more communication. What can’t be helped by communication will probably just sort itself out anyway, especially as psychologists adopt more sophisticated modeling techniques (as opposed to, say, modeling their data with ANOVA or regression, which are only as strong as your interpretations of them), and as the discipline becomes more mathematically rigorous.

If it’s not clear at this point, I think unifying psychology is a bad idea. We can’t even say what it is we’d be unifying, and we’re simply not in a place where a single, global perspective is possible. This is what Evolutionary Psychologists wanted to do, and look how well that turned out. In order to make the certainty of evolutionary theory fit with the uncertainty of psychology, Evolutionary Psychologists had to water down the former to the point where evolutionary biologists can hardly recognize it. Ultimately, I think the disunity of psychology is a good thing. It allows us to keep our options open, and it means that we have a bunch of people looking at the problems of psychology in a bunch of different ways, while allowing us to avoid being too silly (Evolutionary Psychology) or trite (whatever the hell it is that Henrique is saying).

¹Staats, A. W. (1991). Unified positivism and unification psychology: Fad or new field? American Psychologist, 46, 899-912. Quoted in Henriques, G. (2003) The tree of knowledge system and the theoretical unification of psychology. Review of General Psychology, 7(2), 150-182.
²Ibid.
³Kihlstrom , J.F. (2004) Unity within psychology, and unity between science and practice. Journal of Clinical Psychology, 60(12), 1243-1247.
⁴Henriques, G. (2003) The tree of knowledge system and the theoretical unification of psychology. Review of General Psychology, 7(2), 150-182.