The foot-in-the-door technique is also used in many commercial settings and can be illustrated using the door-to-door salesperson who eventually builds up their requests to a final purchase request.[10] In an experiment, subjects were initially asked to have signs in their windows to promote recycling along with varying amounts of incentives ($0, $1, $3) for doing so.[10] This study found that the FITD technique was more effective than any of the incentive strategies in producing behavioural persistence.[10] This is supported by the self-perception theory, which states that the FITD technique is effective only because internal thoughts are what drive people's behaviour. That is, external pressure (such as indebtedness) for compliance is not as effective in increasing compliance.[10]