What is the relationship between behavioral robustness and distributed mechanisms of cognitive behavior?

There is a growing trend in the cognitive sciences to conceive of cognitive behavior as being distributed across brain, body and environment. However, the implications of such distribution for our understanding of biological robustness, which so far has been related to individual-based mechanisms alone, has rarely been discussed in the literature. We used the Evolutionary Robotics technique to examine the relationship between distributed behavioral mechanisms and behavioral robustness. Two kinds of model agents were evolved for a mobile object-tracking task and tested to see whether they can sustain their behavior despite sensorimotor perturbations. The results indicate that a highly distributed realization of behavior can be (i) detrimental, if it is mostly based on factors that are necessary for the behavior, or (ii) beneficial, if it is mostly based on factors that are sufficient for the behavior. Accordingly, we suggest that future discussions of distributed cognition should take into account that there are at least two different possible modes of realizing distributed behavior and that these have a qualitatively different effect on behavioral robustness.