Are Intro Psych Students Lab Rats?

Living in Legoland

For the last two years, I have been learning more about computational modeling, and have been thinking a lot about what models are and what they’re good for.

Put simply, a model is a simplified representation of reality. The goal of a model is to help us understand some aspects of reality by highlighting those parts that are important to the problem at hand and by simplifying or eliminating aspects those aspects of reality that obscure them.

In my Research Methods lectures, I talk about modeling as Living in Legoland. What do I mean? Lego models aren't realistic, but they are useful (and fun) because they capture recognizable elements of reality. For example, when you look at a picture of the Taj Majal built from lego bricks (see above), some sense of the Taj Majal's beauty and grace are communicated to you, even though every one of its details are wrong.

Theater, film, and novels provide MODELS of reality – not reality itself. That is why theater and good novels affect us so deeply and communicate things about human relationships so vividly. Writers bring out only those elements that highlight the key relationships. Everything else is eliminated. Nobody talks over each other. There’s no television mumbling in the background. People speak in clear and complete sentences. Lighting, costuming, and music all highlight those aspects of the situation that the artist hopes to bring out.

Model systems in science

Scientists study – not reality itself – but models of reality. (The school of psychology that tried to capture all of reality objectively – Barker's environmental psychology – is often dismissed as ‘dustbowl empiricism’). This simplification, takes several forms.

• Theories create a simplified and idealized representation of causal processes.

• Experiments attempt to control all aspects of a situation other than that being manipulated in order to create models. We assess the extent to which conclusions that are valid within the experimental context can generalize to other contexts when we evaluate external or ecological validity.

Studying Model Systems.

Importantly, many researchers also utilize model systems. A model system or a model organism is an organism that has been adopted by a wide range of scientists for study. Fruit flies are a great example. Generations of geneticists studied the breeding pattern and then the genes of fruit flies – NOT because fruit flies are inherently interesting, but because they are simple enough that we had some chance of understanding their genes.

C. elegans is a tiny worm currently used by molecular geneticists to do much the same thing. It is a great model system because it is small, non-harmful (it eats bacteria and mold), and beautifully clear so you can see all its organs in a microscope. Better still, you can microinject modified DNA directly into its ovaries, creating genetically modified creatures to test your theories. Arabidopsis is a lovely little white flower that serves a similar function for botanists.

Model Systems in Psychology

Generations of psychologists worked with four main models: pigeons, white mice, rats, and introductory psychology students.

The first three are pretty obvious – anyone interested in psychology has heard of behaviorism and Skinner’s work teaching pigeons to play the piano and rats to do almost anything for a pellet of food.

White mice running through mazes is a truism. In Hitchhiker’s Guide to the Galaxy, Douglas Adam parodied psychologists’ focus on this model by positing that the entire Earth was an experiment designed by a race of hyperintelligent pan-dimensional beings that look exactly like white mice.

The most important contemporary model used by research psychologists, however, is not rats or pigeons, or mice. Most of us study humans: specifically, researchers study students.

Consider the following facts:

• Most research in psychology is done using Introductory Psychology students as research participants;

• Introductory psychology students do not represent the full range of human behaviors and characteristics – even in the culture they live;

Research discussed in How Random Is That? points out that much of what we think we know about human behaviors may be highly influenced by the fact that we typically study college students. One can argue - and the authors of How Random Is That do - that focusing on such a narrow range of research participants has major implications for the field of psychology. I would agree - I am an adolescent developmentalist and I am interested in studying college students specifically because they are different from younger adolescents or from older adults. Studying them as 'typical' strikes me as inherently untenable.

That, however, is not what I want to focus on in this essay about model systems.

I want to make four main points:

• Model systems are useful because when everyone is using the same model organism, results are comparable across studies.

• Model organisms are also useful because they introduce an important aspect of control to experiments. Careful breeding has resulted in lines of mice or worms or flowers that are virtual clones of one another. Minimizing variability in a sample of highly variable human beings helps researchers by making it easier to highlight those aspects that the scientist is interested in. For example, it makes it easier to observe the effects of an experimental manipulation or the correlates of naturally occurring differences such as height, intelligence, or attractiveness.

• It is critical to realize, however, that when we are working with a model organism, we are WORKING WITH A MODEL. It can inform our understanding of the world, but it is not the world itself. For example, everyone knows that we can learn a lot about drugs by studying their effects on mice. No one, however, would think we knew everything about how a drug works if we ONLY knew how it works on mice. There’s a lesson here that psychologists should attend to.

• Finally, introductory psychology students are nowhere near as a good a model system as they used to be.

Huh? Why? Think about the first two points I made above.

A model is helpful to scientists to the extent that when we control our model organism we make comparability across studies easier.

In addition, model organisms introduce an important type of control. For example, you have white mice – all from the same line – that have very limited variability in their genes. You put them in two experimental conditions. At the end, they differ.

Limited variability within each experimental condition because of identical mouse (participant) characteristics means you need much smaller sample sizes to know that mice your two experimental conditions differ. You have smaller standard deviations within groups and it’s easier to detect statistical differences between them.

In non-experimental, naturalistic studies (of intelligence or attractiveness, for example) homogeneity in your participants minimizes uncontrolled variables and thus helps us make a stronger causal argument. For example, the correlation between height and leadership is less likely to be confounded by educational background or social class in a homogeneous class of introductory psychology students than in the population as a whole (controlling for obvious confounds like gender).

The advantage of college students as a model organism, however, depends on a key assumption: homogeneity.

Years ago, college students were very homogeneous. Not as homogeneous as white mice, but typically white, upper middle class, and male. In living memory, people there were written limits on the number of Jews, Catholics, and members of other minority groups that could be admitted to many prestigious institutions. In fact, most experiments were done ONLY on white males because it limited variability even beyond that which the already limited college population would have allowed. This is a major critique Carol Gilligan leveled at psychology in In A Different Voice.

The field has changed. First, people listened to Gilligan and others when they criticized psychology as the study of how white males behaved. Just studying men was seen as unacceptable.

More importantly, COLLEGE has changed. Research is now done at a much broader range of institutions than the elite universities that previously dominated the field. Most adolescents now enroll in college directly after high school (they may not finish, but they do enroll). Many other adults return to school after being out in the workforce. All of these students – a much more diverse population than before – may now become participants in studies of psychology.

Is this good?

It depends what you want to do. I study adolescents. To me, college students are interesting because they ARE adolescents - they have particular qualities that make them different from children, high school students, early adults, middle-aged or older people. They are different from their peers who go straight into the workforace or enlist in the military. To me, any study that purports to find out how people behave by just studying late adolescent college students is immediately suspect. I’m a developmental psychologist. Most of our studies are non-experimental, so we focus on variability rather than work with model systems. I'm fussy about sample populations.

Is it good that there are a broader range of participants in psychology experiments than there were before? On balance, and much to my surprise, I have to say no. As a model system, the homogeneity of college students was an advantage. We didn’t know about all people, but we knew a whole lot about this particular type of person. It made studies very comparable. It allowed us to use smaller sample sizes. It made it easier to create comparable groups for experimental manipulation.

Now students are more variable. All those advantages are diminished. But I don’t think we have changed our methods to test for comparability across experimental conditions, substituted statistical control for experimental control, or heeded to differences in subject pool characteristics in trying to understand why a study done at Oberlin College might not show the same results as one done at Lorain County Community College or UC Berkeley.

Is that disadvantage outweighed by the fact that Introductory Psychology students are now more representative of the population? Only if we recognize that Intro Psych students aren’t representative of the population. They weren’t before. They still aren’t. They’re younger. They’re more advantaged. They’re more academically oriented. They’re less likely to have a disability or to be mentally ill.

It’s like introducing a wild strain into your population of white mice. They’re no longer homogeneous, but they’re not wild either.

It might be better to study white mice, but to systematically test the results of their studies against the real world. Or see the extent to which college students differ from other populations we'd like to understand.

Or, like developmental psychologists, study mice in the wild.

© 2010 Nancy Darling. All Rights Reserved