PEACOCKS, GAZELLES, TURTLES AND US — A LOOK INTO COSTLY SIGNALLING THEORY

“The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick.”

- Charles Darwin

From this quote it seems that it would not take much for the Father of Evolution to feel nauseous, but what Darwin was highlighting, possibly without realising, falls under the (then undeveloped) theory of Costly Signalling (CST). Through a lifetime of work and rigorous research Darwin developed the world’s understanding of natural selection and what is now referred to as “survival of the fittest”. So in this context you can begin to empathise that the sight of the auroral, vivid colours in a peacock’s exorbitant plumage, that must be highly cumbersome and a handicap to survival situations, can make the great Charles Darwin tear what was left of his hair out.

However, from this insight Darwin developed the idea of sexual selection on which the foundations of signalling theory has been built. The cost of possessing such a cumbersome tail whilst simultaneously displaying the size, complexity and symmetry of their colour array of feathers indicates to potential mating peahens that they possess the strength, speed and immunity to survive even with such a burden (Møller & Petrie, 2002).

Another classic example of costly signalling within the animal kingdom is found in Gazelles. Upon noticing a predator, and knowing that predators hunt the weakest in a group, gazelles have been known to demonstrate their energy and physical prowess by leaping into the air repeatedly, called “stotting” or “pronking”. This signals to the predator that they are fit as a fiddle and therefore not worth chasing.

Costly signalling is not just found in the animal kingdom but also in humans. (Note that as psychologists many of us consider humans as just highly intelligent primates, and therefore technically, within the animal kingdom, but for now let’s keep this distinction.) These signals can be from the most specific, such as the practice of foot-binding in China where girls permanently modify the shape of their foot to show wealth and beauty, down to the seemingly normal act of wearing designer brands (Sundie et.al, 2011). These actions are signals to each other that tell people about who we are.

Signalling is not restricted to mating signals but also can be used to explain acts of public altruism and generosity. In evolutionary anthropology, explanations of apparently altruistic or generous acts, such as the sharing of food or other collective goods beyond a close circle of kin have usually relied on notions of reciprocity. Whilst the theory of reciprocity is rich in evidence, there are some questions raised about its ability to explain some instances of cooperation or widespread sharing.

Smith and Bird (2000) created a case study of this human behaviour by observing the native islanders of Mer (Murray Island) near New Guinea, in Australia’s Torres Strait. For Meriam (Mer Islanders), after the death of a loved one there is an official period of mourning declared, called Bood. On the final day of Bood a large feast is held by the mourning family in which anyone can attend, eat and pay their respects. This is one of the best documented forms of public generosity to occur for the Meriam, and requires enough turtles for everyone to eat at the feast.

The family itself cannot provide enough food for all 430 people on the island, therefore turtle hunting parties are created to hunt for enough food. The turtle hunting party consists of six men: the hunt leader, the boat pilot, and “jumpers” who dive into the water to pursue turtles, either with harpoons or their bare hands who risk serious injury when jumping. The turtle hunters give all turtles to the grieving family to supply for the feast, and they receive no reward for the hunt except for the public recognition that they provided a successful hunt. At the feast, a main topic of conversation is about which team provided the most, therefore there is a strong motivation for the hunt to be a success. The cost of turtle hunting is substantial in terms of time, energy, money and potential risk of injury, and yet the hunting crew receive no compensation for their efforts, except their fair portion of the food, so why are the Meriam turtle hunters willing to pay these costs?

This act of public generosity cannot be explained by the reciprocity framework as it does not fit, for example: how can the “donors” (hunters) ensure that the recipients each return the favour when they supply all the food simultaneously?

Instead Costly Signalling Theory proposes that supplying the turtles at a great cost to themselves is a social strategy that can demonstrate their acquisition skills and expand a hunter’s sphere of influence to wider parts of the community. Another benefit is demonstrating their character value to women and potential in-laws to impress them, ultimately to benefit courtships in the future. Therefore, can this act of public generosity be considered an altruistic act after all as the hunters have their own motives to provide a successful hunt, to gain personal social benefit?

When using Costly Signalling Theory to explain behaviours in humans such as this, it becomes unclear whether any action at all can be truly altruistic as the act in itself is a signal to others about one’s value. Under CST the addition of public or social exposure appears to remove true altruism from one’s actions. For example a study found that, when surveying Toyota Prius owners about the reasons why they bought an expensive but highly environmentally friendly car, “environmental conservations” is quite far down the list. Instead, owners reported that the top reason for buying the car was because of the statement it makes about them as a person in that it shows others they must be a caring person (Maynard, 2007). Once the paradigm of public exposure is added, our acts may not be as generous as we would like. For example when donating to a friend’s JustGiving page there is an option of attaching your name and a message. CST would explain that as soon as you add your name and become public-facing in your altruism, you are consciously being motivated by signalling reputation, status and how you are perceived by others.

Furthermore Griskevicius, Tybur & Van Den Berg (2010) found that when priming people with the idea of status they choose more self-sacrificing and “altruistic” products rather than self-indulgent or luxury products, adding to the CST hypothesis that public-facing altruistic acts, rather than being truly generous or altruistic, can instead be subconsciously motivated by status and reputation.

Written by Jack Duddy, Consultant at OCBSP

References

Maynard, M. (2007, July 4). Say ‘hybrid’ and many people will hear ‘Prius.’ The New York Times quoted in: Griskevicius, V., Tybur, J. M., & Van den Bergh, B. (2010). Going green to be seen: status, reputation, and conspicuous conservation. Journal of personality and social psychology, 98(3), 392.

Møller, A. P., & Petrie, M. (2002). Condition dependence, multiple sexual signals, and immunocompetence in peacocks. Behavioral Ecology, 13(2), 248–253.

Smith, E. A., & Bird, R. L. B. (2000). Turtle hunting and tombstone opening: public generosity as costly signaling. Evolution and Human Behavior, 21(4), 245–261.

Sundie, J. M., Kenrick, D. T., Griskevicius, V., Tybur, J. M., Vohs, K. D., & Beal, D. J. (2011). Peacocks, Porsches, and Thorstein Veblen: conspicuous consumption as a sexual signaling system. Journal of personality and social psychology, 100(4), 664.