Hand washing has been proven to be effective in preventing many serious diseases World Health Organization (WHO, 2009). Nonetheless, both the general public and many healthcare professionals fail to wash their hands. Very little research has been conducted outside of healthcare settings to evaluate the adherence of hand-washing procedures. This study investigated if hand washing adherence in a residential setting can be improved with the use of verbal and graphical feedback a probabilistic bonus. Results suggested that the probabilistic bonus had a substantial impact on hand washing performance: more so than signs, educational in-service, and verbal-graphical feedback alone. Reactivity data were collected and showed performance was weak to non-existent throughout all phases until the probabilistic bonus. This final phase improved performance when staff did not know they were being watched, however, performance was only moderate and variable both within- and between-staff