THE HEALTHY CONTROL SUBJECT IN PSYCHIATRIC RESEARCH - IMPULSIVENESS AND VOLUNTEER BIAS

Exciting and demanding biomedical experiments may attract a specific s ubgroup of people as volunteers. In the present study of selection bia s, subjects volunteering in a psychobiological study that included a p otentially painful procedure (lumbar puncture) were compared with thos e who declined to participate, with regard to scores on personality sc ales administered during a previous investigation of the same subjects . Significant differences were Sound on the Eysenck Personality Questi onnaire and Karolinska Scales of Personality Impulsiveness scale, sugg esting an over-representation of impulsive individuals among the volun teers. If the specific subject of investigation has implications for t he type of individual who will participate as a healthy volunteer in b iomedical research, variation will be introduced, affecting the indepe ndent variable, and the conclusions that can be drawn from such resear ch may be questionable.