Interactive theories
It is therefore necessary to understand the process of placebo effects as an active process,
which involves patient, treatment and health professional variables. Placebo effects
should be conceptualized as a multi-dimensional process that depends on an interaction
between a multitude of different factors. To understand this multi-dimensional process,
research has looked at possible mechanisms of the placebo effect.Experimenter bias
Experimenter bias refers to the impact that the experimenter’s expectations can have
on the outcome of a study. For example, if an experimenter was carrying out a study
to examine the effect of seeing an aggressive film on a child’s aggressive behaviour
(a classic social psychology study) the experimenter’s expectations may themselves be
responsible for changing the child’s behaviour (by their own interaction with the child),
not the film.
This phenomenon has been used to explain placebo effects. For example, Gracely
et al. (1985) examined the impact of doctors’ beliefs about the treatment on the patients’
experience of placebo-induced pain reduction. Subjects were allocated to one of three
conditions and were given either an analgesic (a painkiller), a placebo or naloxone (an
opiate antagonist, which increases the pain experience). The patients were therefore told
that this treatment would either reduce, have no effect or increase their pain. The doctors
giving the drugs were themselves allocated to one of two conditions. They either believed
that the patients would receive one of three of these substances (a chance of receiving a
pain killer), or that the patient would receive either a placebo or naloxone (no chance of
receiving a pain killer). Therefore, one group of doctors believed that there was a chance
that the patient would be given an analgesic and would show pain reduction, and the
other half of doctors believed that there was no chance that the patient would receive
some form of analgesia. In fact, all subjects were given a placebo. This study, therefore,
manipulated both the patients’ beliefs about the kind of treatment they had received and
the doctors’ beliefs about the kind of treatment they were administering.
The results showed that the subjects who were given the drug treatment by the
doctor who believed they had a chance to receive the analgesic, showed a decrease in
pain whereas the patients whose doctor believed that they had no chance of receiving
the pain killer showed no effect. This suggests that if the doctors believed that the
subjects may show pain reduction, this belief was communicated to the subjects who
actually reported pain reduction. However, if the doctors believed that the subjects
would not show pain reduction, this belief was also communicated to the subjects
who accordingly reported no change in their pain experience. This study highlights
a role for an interaction between the doctor and the patient and is similar to the
effect described as experimenter bias described within social psychology. Experimenter
bias suggests that the experimenter is capable of communicating their expectations
to the subjects who respond in accordance with these expectations. Therefore, if
applied to placebo effects, subjects show improvement because the health professionals
expect them to.312 HEALTH PSYCHOLOGY