iors that result in filling the need. The two terms, needandrein-
forcer,can sometimes be circular in definition, such as when a need
has to be inferred from the effectiveness of a reinforcer, especially a
conditioned reinforcer. A need, then, may also be viewed as a re-
quirement for a reinforcer (a thirst need requires water; a recogni-
tion need requires attention and praise). Because there are many
reinforcers (especially conditioned reinforcers), some reinforcers
come to be preferred over others. If such preferences become stable,
needs may also be described as preferences (to varying degrees) for
reinforcers. This view of needs as reinforcer preferences is used in
the measurement of needs via questionnaire—the most common
way needs are measured.
Needs measured by questionnaire are typically scaled on a di-
mension of “importance,” that is, in terms of how important a par-
ticular reinforcer is to P. Importance has an affective component: the
greater the importance assigned to a reinforcer, the more affect or
emotion is presumed to be associated with it. Some needs become
more important to P than others, which is to say their reinforcers
become more important to P than other reinforcers. Different needs
may be the more important for different Ps or for the same P at dif-
ferent times. In time, certain needs (usually the most important and
the least important) become more stable than the rest—so much so
that they become characteristic of P.
As a theoretical aside, there is a disagreement among behavior
theorists between those who think “reinforcer class” is the more
important construct (following the lead of Tolman, 1932) and those
who think “reinforcement schedule” is more important (following
the lead of Skinner, 1938). PEC theory is on the side of the rein-
forcer class theorists because we believe that a “reinforcer class”
includes “reinforcement schedule” as a primary characteristic of the
class.
In PEC theory, P attempts to fill its needs by obtaining the
required reinforcers. P’s needs are filled from E for the most part,
which implies that E has some kind of capability to fill needs,
which might be termed reinforcement capability.In addition, some
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