A Usability and Diary Study Assessing the Effectiveness of Call Acceptance Lists

Nuisance or unwanted calls have always been a problem to subscribers of phone services. One possible solution is a network based service that allows subscribers to control the calls they receive by using a call acceptance list. When the call acceptance list is activated, all callers not on the list would be automatically routed to a voice messaging system. Those callers on the list would be allowed to ring the subscriber's telephone. This study assessed the effectiveness of call acceptance lists in reducing unwanted telephone calls. Participants used a prototype telephone-based interface to establish a list of telephone numbers from which they would always accept calls. At the same time, they logged each of their incoming calls in a diary, recording the telephone number that originated the call, and whether they wished to receive the call. The call acceptance list significantly reduced the number of unwanted calls from 12% to 1%. However, this list also substantially reduced the number of wanted calls answered by the subscriber from 88% to 33%. Although a call acceptance list appears to be effective in blocking unwanted calls from reaching the subscriber, the list would also route a substantial number of wanted calls to voice messaging. If the majority of the calls are wanted, the results of this experiment suggest that a call rejection list would be a more effective method for preventing unwanted calls. Fewer wanted calls would be rejected while preventing unwanted calls from ringing through.