Homophily and peer influence are messy business
Some social scientists have recently been getting themselves into trouble (and limelight) claiming that they have evidence of direct and indirect “contagion” (peer influence effects) in obesity, happiness, loneliness, etc. Statisticians and methodologists — and even science journalists — have pointed out their troubles. In observational data, peer influence effects are confounded with those of homophily and common external causes. That is, people are similar to other people in their social neighborhood because ties are more likely to form between similar people, and many external events that could cause the outcome are localized in networks (e.g., fast food restaurant opens down the street).
Econometricians1 have worked out the conditions necessary for peer influence effects to be identifiable.2 Very few studies have plausibly satisfied these requirements. But even if an investigator meets these requirements, it is worth remembering that homophily and peer influence are still tricky to think about — let along produce credible quantitative estimates of.
As Andrew Gelman notes, homophily can depend on network structure and information cascades (a kind of peer influence effect) to enable the homophilous relationships to form. Likewise, the success or failure of influence in a relationship can affect that relationship. For example, once I convert you to my way of thinking — let’s say, about climate change, we’ll be better friends. To me, it seems like some of the downstream consequences of our similarity should be attributed to peer influence. If I get fat and so you do, it could be peer influence in many ways: maybe that’s because I convinced you that owning a propane grill is more environmentally friendly (and then we both ended up grilling a lot more red meat). Sounds like peer influence to me. But it’s not that me getting fat caused you to.
Part of the problem here is looking only at peer influence effects in a single behavior or outcome at once. I look forward to the “clear thinking and adequate data” (Manski) that will allow us to better understand these processes in the future. Until then: scientists, please at least be modest in your claims and radical policy recommendations. This is messy business.
- They do statistics but speak a different language than big “S” statisticians — kind of like machine learning folks. [↩]
- For example, see Manski, C. F. (2000). Economic analysis of social interactions. Journal of Economic Perspectives, 14(3):115–136. Economists call peer influence effects endogenous interactions and contextual interactions. [↩]
Persuasion profiling and genres: Fogg in 2006
Maurits Kaptein and I have recently been thinking a lot about persuasion profiling — estimating and adapting to individual differences in responses to influence strategies based on past behavior and other information. With help from students, we’ve been running experiments and building statistical models that implement persuasion profiling.
My thinking on persuasion profiling is very much in BJ Fogg’s footsteps, since he has been talking about persuasion profiling in courses, lab meetings, and personal discussions since 2004 or earlier.
Just yesterday, I came across this transcript of BJ’s presentation for an FTC hearing in 2006. I was struck at how much it anticipates some of what Maurits and I have written recently (more on this later). I’m sure I watched the draft video of the presentation back then and it’s influenced me, even if I forgot some of the details.
Here is the relevant excerpt from BJ’s comments for the FTC:
Persuasion profiling means that each one of us has a different set of persuasion strategies that affect us. Just like we like different types of food or are vulnerable to giving in to different types of food on a diet, we are vulnerable to different types of persuasion strategies.
On the food example, I love old-fashioned popcorn, and if I go to a party and somebody has old-fashioned popcorn, I will probably break down and eat it. On the persuasion side of things, I know I’m vulnerable to trying new things, to challenges and to anything that gets measured. If that’s proposed to me, I’m going to be vulnerable and I’m going to give it a shot.
Whenever we go to a Web site and use an interactive system, it is likely they will be capturing what persuasion strategies work on us and will be using those when we use the service again. The mapping out of what makes me tick, what motivates me can also be bought or sold, just like a credit report.
So imagine I’m going in to buy a new car and the person selling me the car downloads my credit report but also buys my persuasion profile. I may or may not know about this. Imagine if persuasion profiles are available on political campaigns so that when I visit a Web site, the system knows it is B.J. Fogg, and it changes [its] approach based on my vulnerabilities when it comes to persuasion.
Persuasive technology will touch our lives anywhere that we access digital products or services, in the car, in our living room, on the Web, through our mobile phones and so on. Persuasive technology will be all around us, and unlike other media types, where you have 30-second commercial or a magazine ad, you have genres you can understand, when it comes to computer-based persuasion, it is so flexible that it won’t have genre boundaries. It will come to us in the ordinary course of our lives, as we are working on a Web site, as we are editing a document, as we are driving a car. There won’t be clear markers about when you are being persuaded and when you are not.
This last paragraph is about the “genrelessness” of many persuasive technologies. This isn’t directly on the topic of persuasion profiling, but I see it as critically relevant. Persuasion profiling is likely to be most effective when invisible and undisclosed to users. From this and the lack of genre-based flags for persuasive technology it follows that we will frequently be “persuasion profiled” without knowing it.
No entity without identity: individuating attitudes in social psychology
Social psychologists like to write about attitudes. In fact, following Allport (1935), many of them have happily commented that the attitude is the most central and indispensable construct in social psychology (e.g., Petty, Wegener, Fabrigar, 1997). Here is a standard definition of an attitude: an attitude is
a psychological tendency that is expressed by evaluating a particular entity with some degree of favor or disfavor. (Eagly & Chaiken, 2007, p. 598)
A somewhat more specific view has it that attitudes are
associations between a given object and a given summary evaluation of the object — associations that can vary in strength and, hence, in their accessibility from memory. (Fazio, 2007, p. 608)
Attitudes are also supposed to be important for predicting behavior, though the attitude–behavior link is the subject of a great deal of controversy, which I can’t fully treat here. An extreme, design-oriented view is expressed by a B.F. Skinner-channeling B.J. Fogg:
While Fogg isn’t representative of mainstream, contemporary social psychology, similarly skeptical thoughts are expressed by investigators like Schwartz (2007). On the other hand, one common view of the attitude–behavior link is that it is quite strong (Kraus, 1997), but that (a) many research methods fail to measure attitudes and behaviors with regard to the same entities (Ajzen & Fishbein, 1977) and (b) this link is an important empirical subject, not built into the attitude construct by definition (Fazio, 2007; Zanna & Rempel, 1988).
I’ll set aside for now just how useful attitudes are for predicting behavior. But what should we make of this construct? That is, should we keep it around? Do we expect something like social psychology’s attitudes to be part of a mature science of human behavior?
Maybe I’m a sucker for a good slogan, but when I read psychologists’ on attitudes, I think of Quine’s slogan: no entity without identity. That is, we shouldn’t posit objects that don’t have identity conditions — the conditions under which we say that X and Y are the same object.
This slogan, followed strictly in everyday life, can get tricky: a restaurant changes owners and name — is it the same restaurant? But it is pretty compelling when it comes to the entities we use in science. Of course, philosophers have debated this slogan — and many particular proposed cases of posited entities lacking identity conditions (e.g., entities in quantum physics) — so I’ll leave it that lacking identity conditions might vary in how much trouble it causes for a theory that uses such entities.
What I do want to comment on is how strikingly social psychology’s attitudes lack good identity conditions — and thus have no good way of being individuated. While we might think this doesn’t cause much trouble in this case (as I just noted), I actually think it creates a whole family of pseudo-problems that psychologists spend their time on and build theories around.
First, evidence that there is trouble in individuating attitudes: As is clear from the definition of an attitude provided above, attitudes are supposed to be individuated by their object:
This evaluative responding is directed to some entity or thing that is its object—that is, we may evaluate a person (George W. Bush), a city (Chicago), an ideology (conservatism), and a myriad of other entities. In the language of social psychology, an entity that is evaluated is known as an attitude object. Anything that is discriminable or held in mind, sometimes below the level of conscious awareness, can be evaluated and therefore can function as an attitude object. Attitude objects may be abstract (e.g., liberalism, religious fiindamentalism) or concrete (e.g., the White House, my green raincoat) as well as individual (e.g., Condoleezza Rice, my sister-in-law) or collective (e.g., undocumented workers, European nations). (Eagly & Chaiken, 2007, p. 584)
So, for example, I can have an attitude towards Obama. This attitude can then have internal structure, such that there are multiple evaluations involved (e.g., implicit and explicit). This seems pretty straightforward: it is at least somewhat clear when some cognitive structures share the Obama as object.1
But trouble is not far around the corner. Much discussion of attitudes involves attitudes objects that are abstract objects — like sets or classes of objects– embedded in a whole set of relationships. For example, I might have attitudes towards snakes, Blacks, or strawberry ice cream. And there isn’t any obvious way that the canonical class by which attitudes are to be individuated gets picked out. A person has evaluative responses to strawberry ice cream, Ben & Jerry’s brand ice cream, ice cream in general, the larger class of such foods (including frozen yogurt, gelato, “soft serve”), foods that cool one down when eaten, etc.
This doesn’t just work with ice cream. (Obama instantiates many properties and is a member of many relevant classes.)
At this point, you might be thinking, how does all this matter? Nothing hinges on whether X and Y are one attitude or two…2
The particular trouble on my mind is that social psychologists have actually introduced distinctions that make this individuation important. For example, Eagly & Chaiken (2007) make much of their distinction between intra-attitudinal and inter-attitudinal structure. They list different kinds of features each can have and use this distinction to tell different stories about attitude formation and maintenance. I’m not ready to give a full review of these kinds of cases in the literature, but I think this is a pretty compelling example of where it seems critical to have a good way of individuating attitudes if this theory is to work.
Maybe the deck was stacked against attitudes by my prior beliefs, but I’m not sure I see why they are a useful level of analysis distinct from associations embedded in networks or other, more general, knowledge structures.
What should we use in our science of human behavior instead?
I’m surprised to find myself recommending this, but what philosophers call propositional attitudes — attitudes towards propositions, which are something like what sentences/utterances express — seem pretty appealing. Of course, there has been a great deal of trouble individuating them (in fact, they are one of the kinds of entities Quine was so concerned about). But their individuation troubles aren’t quite so terrible as social psychology’s attitudes: a propositional attitude can involve multiple objects without trouble, and it is the propositional attitudes themselves that can then specify the relationships of these entities to other entities.
I’m far from sure that current theories of propositional attitudes are ready to be dropped in, unmodified, to work in empirical social psychology — Daniel Dennett has even warned philosophers to be wary of promoting propositional attitudes for use in cognitive science, since theory about them is in such a mess. But I do think we have reason to worry about the state of the attitude construct in theorizing by social psychologists.
References
Ajzen, I., & Fishbein, M. (1977). Attitude-Behavior Relations: A Theoretical Analysis and Review of Empirical Research. Psychological Bulletin, 84(5), 8–918.
Allport, G. W. (1935). Attitudes. In C. Murchison (Ed.), Handbook of Social Psychology (Vol. 2, pp. 798–844). Worcester, MA: Clark University Press.
Eagly, A. H., & Chaiken, S. (2007). The Advantages of an Inclusive Definition of Attitude. Social Cognition, 25(5), 582-602.
Fazio, R. H. (2007). Attitudes as object-evaluation associations of varying strength. Social Cognition, 25(5), 603-637.
Fodor, J. A. (1980). Methodological solipsism considered as a research strategy in cognitive psychology. Behavioral and Brain Sciences, 3(1), 63–73.
Kraus, S. J. (1995). Attitudes and the Prediction of Behavior: A Meta-Analysis of the Empirical Literature. Pers Soc Psychol Bull, 21(1), 58-75. doi: 10.1177/0146167295211007.
Petty, R. E., Wegener, D. T., & Fabrigar, L. R. (1997). Attitudes and Attitude Change. Annual Review of Psychology, 48(1), 609-647.
Quine, W.V.O. (1969). Speaking of Objects. Ontological Relativity and Other Essays. New York: Columbia University Press.
Schwarz, N. (2007). Attitude Construction: Evaluation in Context. Social Cognition, 25(5), 638-656.
Zanna, M. P., & Rempel, J. K. (1988). Attitudes: A new look at an old concept. The Social Psychology of Knowledge, 315–334.
- There is still plenty of room for trouble, but this will be common to many representational constructs. For example, there are the familiar problems of what attitudes Louis has towards Superman. Superman is Clark Kent, but it would be odd if this external fact (which Louis doesn’t know) should determine the structure of Louis’ mind. See Fodor (1980). [↩]
- You would likely be in good company, I’m guessing this is a thought that was running through the heads of many of the smart folks in the seminar, “Attitudes and Persuasion”, in which I rambled on about this issue two weeks ago. [↩]