Locals know more than it seems: a new method for revealing collective understanding, tested in three African communities

In the study of human cultural evolution, many theorists hold that technologies are transmitted and improved more through imitation rather than causal understanding. This view stems from results of studies that ask individuals in isolation about technologies they use, appearing to reveal a lack of causal understanding. Here, we introduce a new method to assess the knowledge of a group that allows individuals to view their neighbours' answers before deciding what the best answer might be from among those provided by the group. We asked individuals in three farming communities from Morocco (n = 203), Mali (n = 198) and Ghana (n = 120) to explain the causal processes behind local technologies. Our method reveals that when participants can review the answers provided by their peers, the most popular final answer is more reliable than when individuals provide answers in isolation. This indicates a division of labour in how causal knowledge is stored in the community-while most individuals may have poor causal knowledge, they recognize and defer to the best answer in the group. This shows that collectively the community is more knowledgeable than methods used up to now have indicated. This article is part of the theme issue 'The evolution of collective intelligence'.