The Effect of Commitment on Adoption and Diffusion of Grass Cycling

Using a design that also permitted an assessment of the extent to which any increase in grass-cycling behavior diffused to the neighbors of treated participants, two types of commitment strategies for promoting residential grass cycling (i.e., not bagging grass clippings) were investigated. Baseline data were collected over a period of 4 weeks to determine which residents in each of three homogeneous neighborhoods bagged grass clippings for curbside pickup. A total of 558 houses observed to bag grass clippings during this period were included as participants in the experiment. Following baseline, the neighborhoods were randomly assigned to one of three conditions. Results indicated that participants who made a commitment to grass cycle and to talk to their neighbors had grass bags present significantly less often than either the commitment-only or control participants. This effect was present during the 4-week intervention period and also was sustained during an immediate 4-week follow-up period and a delayed 4-week follow-up period 12 months later. There also was a diffusion effect in which the neighbors of targeted participants showed significantly more grass cycling than controls, and this effect continued to increase through the 1-year follow-up measure. On the other hand, neither commitment-only participants nor their neighbors differed from controls during any period of the experiment.