Factors that influence the Barnum Effect: Social desirability, base rates and personalization
Forer (1949) was the first researcher to demonstrate the "Barnum Effect": People are highly impressed by bogus personality feedback that consists of Barnum statements (high social desirability, high endorsement rate). The present thesis included two studies related to the Barnum Effect. Study 1 aimed to create a pool of statements (Barnum, Rare Virtues and Common Faults) that varied in their levels of social desirability and endorsement rates. In Study 1, Group A, 120 participants rated 185 items for True of Self or Social Desirability. In Study 1, Group B, 70 participants rated the same items for True of Others or Social Desirability. Contrary to expectation, no statement in the two parts of Study 1 met the criteria of a Rare Virtue item (high social desirability, low endorsement rate), suggesting that Rare Virtue items are difficult if not impossible to create. Ten Barnum items were identified in Study 1, as were 10 Common Fault items (high endorsement rate, with lower social desirability than other statements with similar endorsement rates). In Study 2, Barnum and Common Fault items from Study 1 were used to create and test three types of reports: (1) Barnum, (2) Mixed, (3) Common Fault, that came in Personalized and non-Personalized forms. Participants completed a personality test and were given one generalized personality report. Reports were rated using a 13-question Satisfaction Survey. Results showed a main effect of type of report (F (2, 169) = 17.05, p<.001), with Barnum and Mixed reports receiving significantly higher ratings than the Common Fault report. A main effect of Personalization (F (2, 169) = 44.29, p<.001) was also found, with Personalized reports receiving higher ratings than non-Personalized reports. The implications of both studies are discussed.
Farley-Icard, Roberta Lynn, "Factors that influence the Barnum Effect: Social desirability, base rates and personalization" (2007). ETD Collection for University of Texas, El Paso. AAI1444101.