We promote the science of psychology, and we rely on the foundation it provides for the practice of psychology. We generally agree that science is a good thing and that the foundation it provides is a strong one. However, we do not always agree on what to include under the umbrella of true science.
To me, science is the accumulation of knowledge. It is both a process for obtaining that knowledge and a system for organizing it. Most of us point to the scientific method as the process by which scientists acquire new knowledge. This creates some ambiguity because the scientific method is not, in fact, a single well-defined thing. Important elements of the scientific method surely include observation, experimentation, verification and the evaluation of hypotheses. And for many of us, it is important that our hypotheses be falsifiable (with all due credit to Karl Popper). Still, this leaves plenty of room for a diversity of scientific methods.
I doubt that many would disagree with this characterization of science. Tempers start to flare, however, when we get down to the naming of specific scientific methods. There are some among us who will argue that the only true scientific method is the experimental method--random assignment, independent variables, control groups and carefully obtained outcome measures. Quasi-experiments, natural experiments, mere observations and qualitative investigations are castigated as second- or even third-class methods. The scientific gold standard, according to this view, is the true experiment. Anything else is less.
We see an extension of this view when it comes to the evaluation of clinical interventions. The kind of evidence that some scientists demand before placing any confidence in the efficacy of an intervention is the randomized controlled trial (RCT). It is true that well-designed RCTs provide incredibly good knowledge, and the accompanying ability to assess causal relationships can be critical. This does not mean, however, that evidence obtained by any other method is totally irrelevant or less valuable.
What other methods?
Many of the greatest discoveries and advances in the history of science have not been the result of true experiments. Indeed, entire scientific disciplines have thrived and generated new knowledge on the basis of observational methods and instrumentation, not on experimentation. Consider the new knowledge gained from the invention of the microscope or the telescope. Begin to ponder the knowledge already gained and yet to be mined from the mapping of plant and animal genomes. These traditions of science have been enormously generative of new knowledge based on advances in measurement, instrumentation, observation and data analysis and management.
I think psychology can learn an important lesson by studying how other fields of science prioritize their efforts and invest their resources. For example, psychology can benefit by paying more attention to its infrastructure--to such things as instrumentation, measurement, data archiving and data sharing. Increasing our investment in instrumentation and measurement technologies will ultimately create new and better opportunities for experimentation. Learning how to better archive and share our data will preserve our work for the future and maximize the true value of those data. The true experiment is important--but it is clearly only one piece of the scientific enterprise.
Respecting diverse approaches to science
The backbone of scientific psychology--experimental psychology, social psychology, developmental psychology, behavioral neuroscience, comparative psychology--is what many identify exclusively with science. It is not merely coincidence that these subfields are most closely identified with the true experiment. I think for many of us, true experiments equal true science. The unfortunate (and incorrect) inference is that true science derives only from true experiments.
Our scientific enterprise depends on much more than that. Psychology is a rich and productive science because it includes a diversity of approaches--not just experimental methods, but also observational methods, analyses of covariance, measurement technologies, quasi-experiments, modeling and simulations. Much of the science done in the name of psychology draws from the nonexperimental approaches. It is still science--it is the accumulation of knowledge, and it still provides important insight.
There exists a certain elitism among those who identify with the true experimental method. It is a good method, and we have good reason to celebrate it. But it is not the only scientific method, and sometimes it is not even the best scientific method. As a discipline, our greatest advances will only come when we learn to recognize and appreciate the value of the many scientific methods of psychology.
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