barriers. For example, workplaces that are not accessible to wheelchair users would systematically restrict participation, irrespective of the nature and demands of the actual work tasks.
To understand fully how Nagi’s definition of disability and the ICIDH definition of handicap can be applied to the area of work disability, one must understand the concept of social role and tasks from a sociological perspective. Social roles, such as being a parent, a construction worker, or a university professor, are basically organized according to how individuals participate in a social system.
According to Parsons (1958), “role is the organized system of participation of an individual in a social system” (p. 316). Tasks are specific activities through which the individual carries out his or her social roles. Social roles are made up of many different tasks, which may be modifiable and interchangeable. For Nagi, the concept of disability is firmly rooted in the context of health. Thus, for Nagi (1991), health-related limitations in the performance of specific social roles are what constitute specific areas of disability, work being one important area of disability. Roles such as work can be disrupted by a variety of factors other than those that are health related. A change in the economic climate or technological changes, for example, may lead to unemployment totally unrelated to health conditions. These would not represent work disability in the way that Nagi defines this term. As Parsons clarifies:
Roles, looked at that way, constitute the primary focus of the articulation and hence interpretation between personalities and social systems. Tasks on the other hand, are both more differentiated and more highly specified than roles, one role capable of being analyzed into a plurality of different tasks…. A task, then, may be regarded as that subsystem of role which is defined by a definite set of physical operations which perform some function or functions in relation to a role. (Parsons, 1958, p. 316)
Are there limits to this concept of disability from the perspective of role performance? Nagi argues that components of roles—expectations or specific tasks that are learned, organized, and purposeful patterns of behavior—are part of the disability concept. They are more than isolated functions or muscle responses (Sarbin and Allen, 1968; Nagi, 1991). Some tasks are role specific, whereas others are common to the enactment of several roles. For Nagi, to the extent that these tasks are learned, organized, and purposeful patterns of behavior, they are part of the disability concept. It is for this reason that Nagi views the concept of disability as ranging from very basic ADLs to the exquisitely complex social roles such