Clark and Wilson (1961) differentiate between three types of incentives:
Material incentives: tangible rewards often monetary -- wages, fringe benefits, patronage
Solidary incentives: intangible rewards from the act of association -- sociability, status, identification
Purposive incentives: intangible rewards related to the goals of the organization --- e.g., working on an election of a supported candidate
Selective incentives in organizational membership derive from the perceived benefits of inclusion in an "elite" group. Organizations from symphonies to top-tier business schools use selective incentives to build loyal membership and support. For individuals, belonging to an exclusive group like the symphony can bring satisfaction through the status and social contacts it confers (Clark and Wilson in Scott p. 172). Corporations may gain special access to professors and students through their membership in industrial affiliate programs.
The impact of these subtle reward systems are interesting to natural system theorists like Barnard, Simon and Olsen (Scott p. 171). Barnard emphasized the need for various incentives in organizations to maintain member contributions (p.171). Simon added that incentives and contributions are interdependent and require a certain equilibrium for organizational survival (p.171). Often monetary incentives are only partially effective to secure contributions -- perceived exclusivity of membership can be an important natural system strategy.