"Disentangling role perceptions: How perceived role breadth, discretion, instrumentality and efficacy relate to helping and taking charge." 

McAllister, D.M., Kamdar, D., Morrison, E.W., & Turban, D.B. (2007).  "Disentangling role perceptions: How perceived role breadth, discretion, instrumentality and efficacy relate to helping and taking charge."  Journal of Applied Psychology, 92, 1200-1211.