Common knowledge is often integral to our ability to successfully cooperate. This includes our ability to coordinate our behaviors and effectively communicate. It is not enough for common knowledge that two or more agents know the same thing; rather, each must know that each knows this thing, etc. To see the difference, compare two individuals each seeing that their train is departing (shared individual knowledge), versus seeing that each is seeing this (common knowledge). Assuming they intend to travel together, each may remain behind in the first case (each is unsure whether the other sees the train is departing), whereas we expect both to quickly board the train the latter case. Common knowledge, or its lack, makes all the difference here.

The overarching aim of this project is to flesh out our theoretical and empirical understanding of the diverse mechanisms that function to produce and sustain common knowledge under the full range of socio-ecological conditions in which humans live and have lived historically. For it is obvious that mechanisms that work in one social setting may not translate to others. This is easiest to see in the case of increasing social scale. In very small groups, common knowledge often results simply from sharing a perceptual environment. Not so in the case of larger, and hence, more spatially and temporally distributed groups. What strategies have humans devised - either intentionally or unintentionally (i.e., via “hidden hand” forces) - to work around the challenges to common knowledge introduced by increased social scale? How have we managed to maintain the requisite levels of common knowledge for effective cooperation with groupmates, even as we have gone from living in intimate, hunter- gatherer bands, to tribes, chiefdoms, states, and countries?

This project will begin its analysis with the appearance of material symbols in the archeological record. Prototypical examples of such symbols include the use of various pigments to paint the body, personal jewelry, such as shell necklaces, and abstract engravings. The working hypothesis of this stage of the project is that the origins of symbolic behavior reflect a flexible response to the erosion of common knowledge production via old mechanisms due to the increasing size and complexity of human social groups at around 100 kya. Symbolic technologies in part earned their keep through generating common knowledge under these more distributed social conditions.

It is this first stage of the project that I propose to carry out during my visit at the KLI, with later stages to be completed over the following 2 or so years. The project will draw on work from a wide range of disciplines: biology, archeology, anthropology, psychology, and philosophy, among others. Its outcomes will be both theoretical, including an improved analysis of the cognitive scientific demands of common knowledge itself, and empirical, including a cross-cultural and cross-temporal inventory of the diverse mechanisms of common knowledge production in human societies past and present.