I recently put up a clip-job list of all the ideas I’ve been too busy or lazy to flesh out into real posts in the last month. One of the items was about a recent Psych Inquiry commentary I wrote in response to a piece by Jack Block. Tal actually read the commentary (thanks, Tal!) and commented:
…What I couldn’t really get a sense of from your paper is whether you actually believe there’s anything special about the FFM as distinct from any number of other models, or if you view it as just a matter of convenience that the FFM happens to be the most widely adopted model. I suspect Block would have said that even if you think the FFM is all in the eyes of the beholder, there’s still no good reason to think that it’s the right structure, and that with only slightly different assumptions and a slightly different historical trajectory, we could all have been working with a six or seven-factor model. So I guess my question would be: should one read the title of your paper as saying that the FFM is the model that describes the structure of social perceptions, or are you making a more general point about all psychometric models based on semantically-mediated observations?
That’s a great question.
As I think I make clear in the paper, I think it’s highly unlikely that the FFM is isomorphic with some underlying, extra-perceptual reality of bodies or behavior. In other words, I don’t expect we’ll find five brain systems whose functioning maps one-to-one onto the five factors. I could be wrong, but I have seen exactly zero evidence that makes me think that’s the case.
But since I argue in the paper that the FFM is a model of the social concerns of ordinary social perceivers, I think it’s fair to ask whether it’s isomorphic with something else. Like maybe there are five basic, universal social concerns that all humans share, or something like that. And my answer is… no, I don’t think so.
For one thing, I don’t think the cross-cultural evidence is strong enough to support that conclusion. (Being in the same department as Gerard Saucier has helped me see that.) McCrae and Costa have done a very good job of showing that the FFM can be exported to other cultures — if we give people the FFM as a meaning system, they’ll use it in roughly the way we expect. But emic studies have been a lot more varied.
I also am not convinced that factor analysis — a method that derives independent factors from between-person covariance structures — is the “true” way to model person perception and social meaning. Useful? As a way of deriving a descriptive/taxonomic model, absolutely. Orthogonal factor analysis has some very useful properties, like mapping a multidimensional space very efficiently. And there’s a consistent something behind that useful model, in the sense that something is causing that five-factor structure to replicate (conditional on the item selection procedures, samples from certain cultures, statistical assumptions, etc.).
But there’s no reason to think that that means the five-factor structure has a simple, one-to-one relationship to whatever reality it’s grounded in — whether the reality of target persons’ behavior or of perceivers’ concerns. Why would social concerns be orthogonal (and by implication, causally unrelated to one another)? Why, if these are major themes in human social concerns, don’t we have good words for them at the five-factor level of abstraction? (“Agreeableness”? Blech. Worst factor label ever.) Why do they emerge in the between-person covariance structure but not in experimental methods that probe social representation at the individual level (ala Dabady, Bell, & Kihlstrom, 1999)?
As to Tal’s last question (“are you making a more general point about all psychometric models based on semantically-mediated observations?”): I think I say this in the paper, but I don’t think there is, or ever will be, any structural model of personality that isn’t pivotally dependent on human perception and judgment. (Ouch, double negative. Put more straightforwardly: all models of personality depend on human interpretations of personality.) I have a footnote where I comment that the Q sort can be seen as a model of what Jack Block wants to know about persons. I’ll even extend that to models that use biological constructs as their units rather than linguistic ones, but maybe I’ll save that argument for another day…
The Hardest Science 
“all models of personality depend on human interpretations of personality”
I suspect this is true but I’ll play Devil’s Advocate:
Suppose that the amygdala is responsible for the experience of fear, and suppose that the bigger your amygdala the more fear you experience in any given situation. No amygdala, no fear at all. The fear you feel = Amygdala Size x Scariness of Situation. And the amygdala is the only thing that determines fear.
If that were true, then surely you could indeed model one important aspect of personality by positing a factor called “timidity” or “fearfulness” or whatever you chose to call it.
Now in fact this is not true. But it is probably not entirely wrong (it’s not the amygdala it’s the whole amygdala-hippocampal system; it’s not the size it’s the efficiency of neurotransmission; lots of other things do affect fear; etc.) In which case surely it is not entirely wrong to posit a factor of “fearfulness” – and that has nothing to do with how we interpret personality.
Suppose that the amygdala is responsible for the experience of fear
Most of my argument hinges on this opening premise. Before you link amygdala to fear, you need to define what fear is. What is that definition and where did it come from? How can you arrive at a definition without a (human) scientist interpreting human experience and behavior?
(You cannot start from the biology, e.g., by saying that “fear is the set of experiences and behaviors that the amygdala causes” because that makes the supposition that “the amygdala is responsible for the experience of fear” tautological. Even if that weren’t the case, it still sidesteps the definition of what “fear” is. How did the scientist decide what set of experiences and behaviors to measure, and which ones not to measure, in determining the effects of amygdala activity that were subsequently labeled “fear”? It sounds all fuzzy and pomo to say that research design is an interpretive act, but that doesn’t make it wrong.)
Now in fact this is not true. But it is probably not entirely wrong… lots of other things do affect fear
This is a somewhat separate issue, but I’ll go back to my point about isomorphism. I am absolutely not denying that the amgydala is involved, in complicated ways, in the set of experiences and behaviors we call fear. But it is an enormous leap from “involved somehow” to a degree of correspondence so high that brain can be used as a basis for a structural model of behavior. I have never seen evidence for such a one-to-one (or even one-to-few or few-to-one) correspondence between brain structures and Big-Five-style personality factors or component traits like “fearfulness” or “timidness.” It is not a priori logically impossible for them to exist. But empirically, I just haven’t seen it and doubt I ever will.
“Before you link amygdala to fear, you need to define what fear is. What is that definition and where did it come from? How can you arrive at a definition without a (human) scientist interpreting human experience and behavior?”
OK, but there are good interpretations and there are bad interpretations. Surely we can all agree that “fear” is, while not monolithic and not always easy to detect, something that people in our culture feel; it is also reassuring (though I’m not sure it’s strictly relevant) that people in all cultures (so far as I know) and all mammals seem to have the same experience. If I interpret something as being related to fear that might be a sensible interpretation.
Whereas if I believed that everyone except me is a robot, and their behaviour is remotely controlled by an alien spaceship in order to torment me, then I would not have to use the concept of fear to interpret anyone’s behaviour… but then I’d be crazy and paranoid.
Or to take it to extremes I interpret people as “alive” or “dead” all the time. I generally interpret them as being alive. The other day my cat killed a mouse and I came into the room and saw it lying on the floor not moving. My interpretation of its behaviour was “death”. But I was right.
I don’t think I disagree with anything you’re saying. You cannot have an interpretation of reality unless there is a reality to be interpreted. And I reject the strong-constructivist position that the interpretive process is so vexed that science is only about stuff that’s in scientists’ heads (as famously trolled by Alan Sokal). In the paper that started this discussion I think I’m pretty clear that the strong-constructivist position has been unhelpful.
My original point was about structural models of personality traits: how do we divide up the domain of inquiry known as “personality” into units of analysis? That’s an interpretive act, but I don’t see why that’s a problem. Acknowledging interpretation doesn’t deny reality. The fact that there is more than one way to divide it up (and different ways of dividing it up are inspired by different research questions and serve different scientific purposes) doesn’t mean that there is no personality — any more than the fact that there are multiple periodic tables means there are no elements. And c’mon, you brain folks should resonate to this, with your stereotaxic maps and cytoarchitectonic maps and gene expression maps and functional maps and so forth. And I’m no more impressed when someone comes in and tells me that biology will “solve” the problem of personality structure than you would be if I came in with a psychological theory and a functional localizer and told you I was offering the One True Way to Map the Brain.
Hmm, but if someone came to me with a psychological theory, and it was, somehow, absolutely correct, then they would have shown us the one true way to map the brain. It would solve all the problems of neuroscience, except the very boring one of where in the brain each thing happens.
Just as an entirely complete neuroscience would solve all the problems of psychology. Because ultimately psychology is neuroscience and neuroscience is psychology (unless you’re Descartes).
For example, imagine that my psychological theory is Skinnerian behaviourism: all behaviour is learned, by the process of operant conditioning (do something, get a reward, do it again; get punishment, don’t do it again.)
If that were entirely true and the whole truth, then the brain would consist of, presumably, some input areas (sensory), some output areas (motor), and a learning bit.
Conversely if I were a neuroscientist and my theory of the brain was that the brain is a huge homogeneous mass of cells and they learn connections by a simple Hebbian process (cells that fire together wire together), the only complication being that some cells also get input from senses and some output to the spinal cord; and if that were entirely true, it would I think explain all psychology. It wouldn’t explain all behaviour because people have different learning experiences so they would behave differently, i.e. we have cultural and social differences; but you would know exactly how to explain these differences in terms of basic learning processes.
Now in fact both of these hypothetical theories are wrong, and neuroscience and psychology are two separate fields… but the point is that neuroscience can inform psychology and vice versa. So I think neuroscience could inform personality psychology. I don’t think it can do so right now. but it could.
For someone with “skeptic” in your name, those are some awfully optimistic hypotheticals you’re starting from.
Kidding aside, I totally agree with you that psychology and neuroscience can inform each other. I’m not opposed to cognitive or social neuroscience. Some of my best friends (and collaborators) are cognitive and social neuroscientists. I haven’t gone that direction mainly because I don’t see it as fruitful yet for the particular psychological phenomena that I study (which are on the more macro end of psychology). I expect that someday it will be. I think that’s pretty much what you’re saying too.
But… even if I temporarily adopt your hypotheticals, I’m not sure that a complete and correct unified theory of psychology would solve all of the problems of neuroscience. It would certainly be an enormously helpful roadmap. But in addition to the “where” questions (which I totally agree is boring on its own), there are a bunch of “how” questions that neuroscientists seem pretty interested in. (“How” as in, how is that actually implemented in the biological brain? Which even a complete theory of psychology won’t tell us, though it can point us in some helpful directions.)
Going the other direction, I do believe as a remote abstraction (because I’m a philosophical materialist) that a complete account of the biology of the brain/body and its interactions with the world could explain psychology. But in practice, I find that abstraction frequently unhelpful. To borrow an analogy from Eric Turkheimer, we could in principle explain all of the behavior of a computer at a purely physical level, electrons traveling around in circuits. And some behaviors have coherent physical explanations (“bad disk sector”). But others don’t. Thus it will never make sense to debug software errors with a soldering iron, even if we had the depth of understanding to do so.