Social learning through networks: The adoption of new agricultural technologies in Ghana

There is a natural way of thinking about this process of "social learning" that has motivated much of the existing work on the topic (Besley and Case; Foster and Rosenzweig; Munshi). Consider the village (or other appropriate social group) as a unit of learning engaged in a process of collective experimentation. Each farmer in the village observes the farming activities of each of the other farmers, including of course those who are experimenting with the new technology. Each farmer then updates his or her own opinion regarding the technology using this information, makes decisions regarding cultivation for the next season, and the learning process continues. There are two important assumptions about the nature of social learning in this story. First, each farmer receives information on the outcomes of experiments from every other farmer in the village. Second, each farmer observes other farmers' experiments with no loss of information. Few would argue (and none of the cited authors argue) that these assumptions are literally true, but they seem to be a reasonable starting point for a discussion of learning about agricultural technology in a village context. However, both assumptions are strongly contradicted by data from pineapple farmers in a set of Ghanaian villages.