Although these authors equate high levels
of effort with simply working hard, several theoretical definitions
are much broader. According to Locke et al. (1981)
it is useful to distinguish three subdimensions: direction,
amplitude, and duration of the action. Later, Campbell
(1990) implicitly referred to three related choices an employee
makes, namely the choice to perform at some level
of effort for some specified time, and Kanfer (1990) continued
with this idea on the three dimensions as critical
components of motivational outcomes: what a person does
(direction), how hard a person works (intensity), and how
long a person works (persistence).