Social learning in agriculture: does smallholder heterogeneity impede technology diffusion in Sub-Saharan Africa?

Evaluating a large-scale program for dairy farmers in Uganda, we show that a simple version of the "contact farmer" extension model can meaningfully increase smallholder farmers' revenues. While the program provides no monetary incentives, we find evidence that two other ingredients â?? backstopping by professional extension agent and advertising pro-social motivation â?? reinforce its impacts. Though it has been hypothesized to be a major impediment to social learning in Sub- Saharan African agriculture, we do not find smallholder heterogeneity to condition the effectiveness of the approach: farmer trainers trained to take this heterogeneity into consideration do not perform better; moreover, we find no statistical evidence that program effects vary by farmers' characteristics.