Randomly selected residents of New Zealand were asked to participate in a curbside recycling trial. Two weeks before the first collection they received a letter from the mayor that included an explanation of the trial and a telephone number for more information. A week later the recycling bins were delivered individually to the participants along with a "Curbside Recycling Kit". Included in the kit was a letter that welcomed the participants to the trial, a bumper sticker that read "Recycle: Show You Care", and a small sticker for their mailbox that identified them as participants. As well, an information guide was included that explained why the participants should recycle, what is recyclable, and how to recycle. There were three different groups of participants. The first group was simply given the bins and recycling kit. The second group was given the bins, the recycling kit and was asked for a verbal commitment. The third group was given the bins and the recycling kit, asked for a verbal commitment, and asked to mail an $8.00 payment for their bins in a postpaid return envelope. Thus, two of the three groups were asked for a verbal commitment to recycle. To ensure that verbal commitment was consistent for both of these groups, a script was given to the volunteers. Participants were thanked for their time, explained the goal of the trial, and asked to make a verbal commitment to recycle.
Groups 2 and 3, the verbal commitment groups, recycled considerably more than the control group (who were not asked for a verbal commitment). Only 47% of the participants in group 3 actually paid for their recycling bins and there was no significant difference in recycling behavior found between those who paid for their bins and those who did not. Overall, the trial demonstrates that emphasis should be placed upon reinforcing verbal commitments because they are an easy, efficient, and cost-effective method of increasing recycling participation.