Recently, Evolution and Human Behavior (an interdisciplinary journal focusing on the scientific theory of and empirical research on human behavior) published a paper by Daniel Brian Krupp, Lisa M. DeBruine, and Pat Barclay entitled “A cue of kinship promotes cooperation for the public good.” In this paper, Krupp, DeBruine, and Barclay discuss their recent findings in a public goods game (PGG) using self-resemblance as an indication of relatedness.
Relatedness has always been of interest to social biologists, and it has been hypothesized that kinship is one of the primary selection factors in the evolution of cooperation, altruism, and other social complexity observed with the animal kingdom, particularly in Homo sapiens. According to kin selection theory, the overall fitness of an allele can be promoted by closely related individuals assisting each other thus serving to advance the survival of said allele. There is a catch, however. Members of a group contributing to the public good can fall subject to freeloaders who attempt to cheat the system by taking the benefits of the cooperative society while donating little or sometimes nothing at all. This is referred to as the “tragedy of the commons,” and is of key interest to those studying the evolution of social alliances.
Previous studies have shown that facial self-resemblance increases trust, which led Krupp, DeBruine, and Barclay to their hypothesis that facial self-resemblance is used by humans as a cue to give their resources to a common cause, thus assisting the public good. For the public goods game they set up, they predicted that donations would increase with an increase in perceived degree of relatedness within a group, or kin density.
Fig. 1. Facial resemblance manipulation. The shape and color information of an unknown face (left) and a known face (center) were blended in a 60:40 ratio to create a composite face (right).
For their experiment, these scientists recruited introductory psychology students under the pretense that the students would be participating in an online study of investment decisions. They were photographed and these pictures were used to create morphs for the self-resemblance study (Fig. 1). They created two different categories of morphs: self-resembling and stranger. The PGG was presented as an online study where the photographs that appeared on the computer screen were said to be other participants at different universities, but were in fact the pre-prepared morphs programmed to be either cooperators or free riders. During the PGG, the participants donated dollar amounts to the public good. This set up provided the authors with an opportunity to see if facial self resemblance increased, decreased, or had no effect on the dollar amount donated to the public good. Using ANCOVA techniques, they found that participants would contribute more to the common good when playing with self-resemblance morphs than with stranger morphs. They attribute this to the proposal that facial self-resemblance was and is a cue of kinship.
Overall, I was disappointed with this particular study. I think the basis for the experiment, the idea that kinship can act as a sort of selection factor but can be subject to the possibility of freeloaders, is incredibly interesting. The evolution of cooperation and altruism is amazingly complex, and there are plenty of questions that could be asked about it. As the authors note, it is impressive that their photographic morphs utilized in a laboratory setting produced results that corroborate the idea that facial self-resemblance is an important cue in kin recognition. However, I am just not sure that this was one of the questions that (at least for me) was all that pressing. Common sense tells me that someone who looks more like me is probably more closely related to me than someone who does not. In my opinion, this study does not contribute that much to human knowledge and does not illuminate complicated questions, but rather takes something that any layperson could tell you and gives it empirical evidence.
KRUPP, D., DEBRUINE, L., BARCLAY, P. (2008). A cue of kinship promotes cooperation for the public good. Evolution and Human Behavior, 29(1), 49-55. DOI: 10.1016/j.evolhumbehav.2007.08.002