Abstract
Social group dynamics are a defining topic of psychological science, yet the field still lacks methods of tracking groups with precision and control. Previous methods have been hampered by limitations either to external validity (e.g., ecologically deficient environments) or to internal validity (e.g., quasi-experimental designs), but a new technique-which we term in vivo behavioral tracking (IBT)-resolves this trade-off. Through IBT, we track large numbers of people in controlled environments over time, while storing precise behavioral data that can be linked to information regarding participants' attitudes, personality, and demographics. In this article, we describe the fundamentals, assumptions, and challenges of IBT methodology. We also compare IBT to other tracking methods and illustrate some insights it has provided into group formation and cooperation. We argue that IBT is a highly valid and surprisingly feasible method of studying groups that should be used alongside more traditional forms of data collection.