INTERPAKS; see also C07214, Aims to show that it can be of great advantage to the design of a rural development project if the cognitive strategies which lie behind farmers' decisions to adopt new technology are understood. This is done by using a case study of an agronomic recommendation of the Plan Puebla in Mexico which did not diffuse. Of the 1973-4 recommendations, the one to increase the number and change the timing of fertilizer applications was the non-adopted recommendation. The theory of choice used in this study assumes that people choosing between two alternatives do not make complex calculation of the overall worth or utility of each alternative. Instead people tend to use procedures which simplify their decision making calculations.