cal, maximal, or some in-between level of effort. As many commentators of
the academy appear to agree, there is great difficulty in efficiently making the
prediction of typical behavior from observations under what may be maxi-
mal effort conditions.
Effort Demanded Versus Effort Allocated
The literature on attention and performance (e.g., Kahneman, 1973; Norman
& Bobrow, 1975) has an excellent set of models that relate attentional effort
to task performance. However, validating such models has been extremely
difficult (e.g., see Navon, 1984), partly because it is exceedingly difficult to
get participants to provide finely graded levels of effort to a task that is more
than trivially easy (e.g., see Wood, Mento, & Locke, 1987). The methodolo-
gies of secondary-task, dual-task, or timesharing procedures have been
adopted in an attempt to examine the relations between effort and perform-
ance, to mixed success (e.g., see Ackerman, 1984). We believe that the reason
for the difficulty in obtaining graded levels of effort from individuals in the
laboratory, and in the field, is due to an underlying constraint—that of the re-
lationship between the effort demanded by the task and the individual’s de-
sired level of effort. That is, as we have seen in numerous studies, difficult
tasks (as long as they are not impossibly difficult) demand greater amounts of
attention from the participants, and as such, many (but not all) participants
end up allocating more attention to the task than they may have intended to,
prior to engaging the task. In some sense, the task draws-in the participant;
much in the way that inclement weather or traffic problems will cause the in-
dividual to have a substantial increase in latency and decrease in attention to
a cell-phone conversation. The long-term effects of task demands—whether
they are higher or lower than the individual’s typical intellectual effort are
unknown. It may be that, consistent with a generalization of Helson’s (1948)
adaptation level theory, the individual may shift in typical level of effort to
better adjust to the demands of the ongoing tasks. If something like this
scheme actually operates, it may be that typical intellectual engagement is not
necessarily stable over the adult life-span, but it may change in predictable
ways in conjunction with task–job demands.
Longitudinal Study and Developmental Hypotheses
The PPIK theory is essentially a developmental approach. However, in the
absence of longitudinal data, it is not possible to ascertain the nature of inter-
actions among cognitive, affective, and conative determinants of adult intel-
lectual development. It is likely that, as proposed by Holland (1959), that in-
terests, personality, self-concept, and ultimately abilities and knowledge
develop in an interactive fashion. Initial success at a particular task or family
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