Volunteer bias in human sexuality research: evidence for both sexuality and personality differences in males.

The extent to which personality, social behavior, and sexuality differed in undergraduate males under two different types of recruitment, volunteer and nonvolunteer, was investigated. Nonvolunteers (N = 160) were ostensibly recruited for a study on personality, and volunteers (N = 204) were overtly recruited for a study on human sexuality. Both samples completed the same personality, social behavior, and sexuality questionnaires. Volunteers were found to be more sexually experienced, more interested in sexual variety, and more erotophilic than the nonvolunteers. In addition and contrary to most prior research, the volunteer and nonvolunteer samples also differed in personality and social behavior, with the volunteers being higher in sensation seeking and lower on measures of social conformity and rule-following behavior than the nonvolunteers. Results extend prior research suggesting limits to the generalizability of some human sexuality research.