Cooperation between individuals is a rather common observation in the animal kingdom. Cooperation is likely favored by evolutionary pressures that provide an advantage to the cooperating partners. Love birds, for instance, regurgitate food to feed their partner. Bats have a similar behavior. One of the questions that psychologists and ethologists have been wondering about is whether the brain represents the preferences of others when performing these behaviors. The question has been framed as whether or not non-human animals have a theory of mind – whether they have neural circuits that represent the preferences, motivations, or goals of the other individual. There is no easy answer to this question, but a recent study provides evidence that male Jays can adjust the food they share based on expectations about their partner’s changing preferences.
The study, published by Ostojic and colleagues in PNAS1, uses a well-known behavioral characteristic that many animals display: specific satiety. The phenomenon is that animals get “tired” of food they had access to recently and prefer novel food items. Leanne Boucher has covered this subject in another post on this blog.
The team of scientists directed by Nicola S. Clayton asked whether male Jays sharing food with their female partners would anticipate specific satiety and provide their partner with foods they had less access to. The females were fed mealworm larvae or wax moth larvae, two delicacies in the jay milieu. During this feeding period, the male was given a chance to observe the female eating. He was then offered the two foods that he could share with the female. The authors observed that male jays were less likely to give their partner wax moth larvae when they had previously observed their partner eating that food than when they had previously observed them eating mealworm larvae.
Many controls were made to exclude some explanations for this behavior. First, it is possible that the male may have been cued which food to take by the females. For instance, females might have emitted some sounds during the choice process to influence the male. To control for this, the experimenters have reproduced the same experiment with a veil separating the male and the female during the pre-feeding session. That way, only the possibility for the male to observe was blocked, while potential behaviors of the female partner could still be effective during the choice session, when the veil was removed. In these sessions the male did not adjust its food sharing based on the pre-fed food. This means that the observation phase is necessary to influence the choice of the male.
To evaluate the degree to which the male was distinguishing between the preferences of the female and his own preferences, they made sessions in which they offered the foods to the male at the end, with no possibility for sharing. They show that males do not, as a result of observing the female eating specific food, develop a food satiety for themselves – they eat the two foods in similar proportion. This is important as it shows that males can adjust their eating and sharing of food separately for themselves and their partner.
This new behavioral setup is an important progress toward understanding how the brain represents the state of others in animals. The behavioral criteria that have been controlled for show that food sharing among partners in jays respect some of the basics characteristics that scientists would be looking for to assess whether an animal can attribute states to another. The paradigm opens up interesting possibilities, including potential investigation of the brain mechanisms underlying those behaviors.
1. Ostojic L, Shaw RC, Cheke LG, Clayton NS (2013) Evidence suggesting that desire-state attribution may govern food sharing in Eurasian jays.. PNAS, Epub ahead of print.