When two heads are better than one : the independent versus interactive benefits of collaborative cognition

Previous research has shown that two heads working together can outperform one working alone, but whether such benefits result from social interaction or the statistical facilitation of independent performance is not clear. Here I apply Miller’s (1982; Ulrich, Miller & Schröter, 2007) race model inequality (RMI) model to distinguish between these two possibilities. This model was developed to test whether response times to two signals compared to one were especially fast because the observer could detect a signal in either of two ways (i.e., separate activation models) or because both signals contributed to a common pool of activation (i.e., coactivation models). I explored the independent versus interactive benefits of social collaboration in four experiments. In a first experiment I replicated Miller’s classic finding that coactivation underlies the faster responses to two targets than one during simple visual search by a single individual. However I found that two-person team performance was no faster than the performance of two independent individuals. Reasoning that the division of the cognitive load between collaborators was important to achieving collaborative performance gains, I employed a more complex enumeration visual search task in three subsequent experiments. With this task I found that performance by two-person teams exceeded the fastest possible performance of two independent individuals. This violated Miller’s RMI and indicated that interpersonal interaction produced the collaborative cognition performance gains. I then linked the magnitude of these collaborative gains to features of the interpersonal interaction between team members, including verbal communication, affiliation, and non-verbal communication such as posture, gesture, and body movement. Together these experiments serve as an important proof of concept that Miller’s RMI can be applied to differentiate between the independent and interactive benefits of collaborative cognition. In addition they demonstrate that the interactive ...