Social Learning Through Networks: The Adoption of New Agricultural Technologies in Ghana∗

The adoption of new technology is a central feature of the transformation of farming systems during the process of economic development. There is a rich tradition of social science research, therefore, on the adoption of new technologies (Evenson and Westphal; Feder, Just and Zilberman). Much of this research has focused on the problem faced by individual farmers as they decide whether to adopt a potentially proÞtable new technology. How do farmers learn about a new technology? There are many possible sources of information about the new technology (Rogers). A farmer may learn from his or her own experimentation with the technology. Advice and technical information may be available from the extension service or the media. If there are many farmers in somewhat similar circumstances, then the process of learning about the new technology may be social. Farmers may learn about the characteristics of the new technology from their neighbors experiments. There is a natural way of thinking about this process of social learning that has mo-tivated 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 experiment-ing 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