Multiple claims in ads reducing their effectiveness

Zukier (1982) asked which student has the higher Grade Rank Average.

Tom spends about 31 hours studying outside of* class in an average week. Tom has one brother and two sisters. He visits his grandparents about once every 3 months.* He once went on a blind date and shoots pool about once every 2 months.

If you are similar to the students in Zukier’s study, you would believe that Tim is smarter than Tom. Zukier found that including irrelevant and nondiagnostic information (such as information on siblings, family visits, and dating habits) that has nothing to do with the issue at hand can dilute-that is make less potent-the impact of relevant information (that both Tim and Tom spend a lot of time studying).