I am not accusing any of the researchers or doctors of unethical behavior. However, my skepticism gear kicks in just like overdrive in the car. Consistency People want to appear consistent in their actions. Two devices were used. The second device used was for the hostess to pause and wait for an answer.
People are uncomfortable with silence.
People feel they have to fill a quiet space. Once the customer agreed to call, the customer, to appear consistent with his own commitment to him or herself had to make the call. The evidence for this is old but still true. If you stop on the sidewalk and look up at nothing in particular, it is likely that about four percent of the people who pass will look up as well. If you have five people stop and look up, the passers by who look up will jump from about 4 percent to 18 percent.