 Dime in the Phone Booth. The psychologists Isen and Levin had an experimental group find a dime in the coin return slot of a phone booth, whereas the control group did not. Individuals in both groups subsequently had a chance to help pick up dropped papers. 88% in the experimental group helped; only 4% in the control group did (Isen and Levin 1972). There were replication problems with this study, but there are many other studies on the effect of mood on helping which found a similar pattern (see Miller 2013: chapter 3).