Subject Recruitment Bias: The Paid Volunteer Subject

To assess the potential bias introduced by subject recruitment procedures, differences in perceptual style, personality, and performance on an auditory selective attention task were investigated for a sample of 47 female, volunteer research participants. Half of the subjects (N = 24) had been recruited as unpaid volunteers while the others (N = 23) received 2. 50 per hour for their participation. Stepwise discriminant analysis indicated that unpaid volunteers tended to be significantly more interpersonal in orientation, were more field-dependent, and committed fewer omission errors on a selective attention task than subjects who had volunteered for pay. The findings were discussed in terms of the problems associated with generalizing from one sample to other samples and to the criterion population as a function of experimental boundary conditions.