Volunteering for extra-hazardous duty

What type of man volunteers for the hazardous work of participating in studies pertaining to protection against exposure to radiation? 489 cadets volunteering under experimental conditions to be exposed to cold or radiation were compared to 665 who did not. Some were asked to volunteer publicly and some privately. Psychological test scores and other data were used to compare the various conditions. "You can influence the amount of volunteering by manipulating the experimental conditions for volunteering." Volunteers were generally superior to nonvolunteers.