486 Part VI Learning-Cognitive Theories
were allowed two puffs immediately after doing the desired behavior. If the stimulant
simply increases general activity levels, there should be no systematic preference for
one reinforcer over the other (compared to baseline preferences). Additionally, after
the experimental session ended, they were allowed a period in which they could smoke
as much or as little as they wished (free smoking session).
However, results showed that smoking levels in both the experimental choice
(compared to money) and in the free smoking sessions increased in proportion to
d-amphetamine. The higher the dose of d-amphetamine, the more the participants
smoked. Even more importantly, however, smoking was chosen over money in the
choice session in direct proportion to the amount of d-amphetamine administered.
Therefore, the stimulant must increase the reinforcing value of nicotine specifically
and not the other reinforcer (money). In short, the answer to the question of whether
reinforcers can change their value over time and in combination with other stimuli
is “yes,” and in this case nicotine can become even more reinforcing in the pres-
ence of psychomotor stimulants.How Personality Affects Conditioning
If conditioning can affect personality, is the reverse also true? That is, can person-
ality affect conditioning? Several thousand studies with both animals and humans
have demonstrated the power that conditioning has to change behavior/personality.
With humans in particular, however, it is clear that different people respond dif-
ferently to the same reinforcers, and personality may provide an important clue
about why this may be so.
Returning to research on d-amphetamine and smoking, for example, there
appear to be systematic individual differences on the effect; that is, it works for some
people but not others. Just as in the previous study, Stacey Sigmon and colleagues
(2003) studied the effects that d-amphetamine has on smoking using two different
reinforcers: cigarettes and money. In addition to trying to replicate the finding that
psychomotor stimulants specifically increase the reinforcing value of nicotine com-
pared to money, they wanted to examine whether there were any individual differ-
ences in the effect. If there were, then what might be some possible explanations?
Participants were adult smokers (averaging 20 cigarettes per day) between
the ages of 18 and 45, with a mean age of 21; 78% were European American
and 61% were female. To be included in the study, participants had to test neg-
ative for drugs other than nicotine and report no psychiatric problems, and
women had to practice a medically acceptable form of birth control and test
negative for pregnancy. Participants were informed that they could receive vari-
ous drugs, including placebos, stimulants, and sedatives, and that the purpose of
the study was to investigate the effects of these drugs on mood, behavior, and
physiology. Participants were paid $435 if they completed all nine sessions.
The general procedure included nine sessions, the first of which was a 3.5-hour
session to acclimate the participants to the procedures and equipment; no drugs were
administered in the first sessions. Sessions 2 through 9 lasted 5 hours each and
included breath tests to ensure no prior smoking had occurred. Baseline measures
included pre-session questionnaires and physiological measures such as heart rate, skin
temperature, and blood pressure. Also, each participant lit a cigarette and smoked at