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Interpersonal Expectancy Effects and Human Performance Research
Honica J. Harris and Robert Rosenthal
Humans have long tried to surmount their traditional limitations and to
increase their performance. Long ago such efforts were aided by social
institutions of religion, proto-meticine, and magic. More recently, such
efforts have been aided by social institutions of science ant its associated
technologies. Systematic programs have been developed with such aims as
improving communication, accelerating learning, ant increasing conscious
control over physiological processes. Because the promise of enhancing huma..
performance is so appealing, considerable resources, both in terms of time ant
money, are being invested in these programs. The time has come to step back
and evaluate human performance technologies so that resources may be directed
more appropriately. The purpose of this paper is to aid in such an evaluation.
We will focus specifically on the possible influence of interpersonal
expectancy effects on several human performance technologies. The paper
advances in three steps: First, we describe the methodological, theoretical,
and empirical issues relevant to the study of expectancy effects, including
how expectancy effects are mediated. Second, we describe each of several types
of human performance research and speculate on the extent to which expectancy
effects may be responsible for the experimental results. Finally, we discuss
more generally how the literature on expectancy effects can be applied to the
development~and evaluation of human performance technologies.
Interpersonal Expectancy Effects
Def ini~cion
~ .
An interpersonal expectancy effect occurs when a person (A), acting in
accordance with a set of expectations, treats another person (B) in such a
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manner as to elicit behavior that tends to confirm the original expectations
(Rosenthal, 1966, 1976~. For example, a teacher who believes thee certain
pupils are especially bright may act more warmly toward them, teach them more
material, and spend more time with them. Over time, such a process could
result in greater gains in achievement for those students than would have
occurred otherwise.
The concept of an expectancy effect was first introduced by Merton (1948)
in his discussion of the self-fulfilling prophecy, which he defined as "a
false definition of the situation evoking a new behavior which makes the
originally false conception come true" (p. 195). The first systematic
application of the concepts of expectancy effects in the field of psychology
came in the 1960s with a program of research on experimenter expectancy
effects (e.g., Rosenthal, 1963). This research demonstrated that the
experimenter's hypothesis may act as an unintended determinant of experimental
results. In other words, experimenters may obtain the results they predicted
not because the relationship exists as predicted in the real world but because
the experimenters expected the subjects to behave as they did.
Evidence for Interpersonal Expectancy Effects
Although originally fraught with controversy, the existence of
interpersonal expectancy effects is no longer in serious doubt. In 1978,
Rosenthal and Rubin reported the results of a meta-analysis of 345 studies of
expectancy effects. A meta-analysis is the quantitative combination of the
results of a group of studies on a given topic. This meta-analysis showed that
the probability that there is no relationship between experimenters'
expectations and their subjects' subsequent behavior is less than .0000001.
The practical importance of expectancy effects was also substantial; the mean
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ef feet size of expectancy ef fects across the 345 studies was equivalent to a
correlation coef f icient of . 33 .
This meta-analysis also investigated the importance of expectancy ef fects
within a wide variety of research domains. There were eight categories of
expectancy studies: reaction time experiments, inkblot tests, animal learning,
laboratory interviews, psychophysical judgments, learning and ability, person
perception, and everyday situations or field studies. Although effect sizes
Wearied across categories, the importance of expectancy effects within each
category was firmly established. These results suggest that expectancy effects
may occur in many different areas of behavioral research and emphasize the
importance of taking into account the possibility of expectancy effects when
des igR ing and conducting studies.
Although initially focused on the psychological experiment as the domain
of interest, research on expectancy effects turned quickly to other domains
where expectancy effects might be operating, domains such as teacher-student,
employer-employee, and therapist-client interactions. Over the years, research
interest has also turned from merely documenting the existence of expectancy
effects to delineating the processes underlying expectancy effects.
Methodological Implications of ExDectancv Effects
Experimenter expectancy effects are a source of rival hypotheses in
accounting for experimental results. In other words, a given result could be
caused not by the independent variable under investigation but rather by the
experimenter's expectation that such a result would be obtained. As rival
hypotheses, expectancy effects can be considered a threat to the internal
validity of a study; they are a source of systematic bias rather than random
error. Consequently, expectancy effects present a serious danger to the
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interpretation of results: Increasing random noise merely makes it more
difficult to obtain significant results, but increasing systematic bias can
result in completely erroneous cone lus ions .
Experimenter expectancy effects are a potential source of problems for
any research area, but they may be especially influential in more recent
research areas lacking well-established findings. This is because the first
studies on a given treatment or technique are typically carried out by
creators or proponents of the technique who tend to hold very positive
expectations for the efficacy of the technique. It is not until later that the
technique may be investigated by more impartial or skeptical researchers, who
may be less prone to expectancy effects operating to favor the technique. Many
of the human performance technologies of interest in the present paper are
relatively recent innovations, and thus may be especially susceptible to
expectancy effects.
In principle, expectancy effects could be investigated by introducing
expectations as a manipulation in addition to the independent variable of
theoretical interest. This method, which will be described in detail later,
allows the direct comparison of the magnitudes of the effects due to the
phenomenon and effects due to expectancies. Another approach, perhaps even
richer theoretical ly, is to examine directly the processes underlying
expectancy effects as they occur in various areas. In some areas, such as the
area of teacher expectancy effects, a considerable amount of research has been
conducted in this manner, and there is now a good general understanding of
what variables are important in mediating teacher expectancies. However, in
other areas, such as the human technologies of interest here, this background
research is lacking. The best that can be done in such cases is: (a) to
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analyze the situations of interest, (b) to determine whether mediating
mechanisms shown to be important in traditional research areas are likely to
be present in the new areas, and (c) to estimate the extent to which
expectancy effects court be influential in the new area. The present paper
undertakes such an analysis.
Mediation of Interpersonal Expectancy Effects
Basic Issues
A primary question of interest with respect to expectancy effects is the
question of mediation: How are one person's expectations communicated to
another person so as to create a self-fulfilling prophecy? This question in
turn can be broken down into two components. The first component is the
differential behaviors that are displayed by the expecter as a result of
holding differential expectancies (the expecter-behavior link). For example,
in what ways do teachers treat their high expectancy students differently? The
second component is the differential behaviors that are associated with actual
change in expectee behavior and self-concept (the behavior-outcome link). For
example, what teacher behaviors result in better academic performance by the
students? Both these aspects are critical in understanding expectancy
mediation, for even if we could show an enormous effect of expectancy on
expecter behavior (e.g., teachers smile more at high expectancy students),
that behavior would not be important in expectancy mediation unless it
actually impacted on the expectee to create better outcomes (e.g., being
smiled at leads to better grades).
The Four-Factor "Theory"
Rosenthal (1973a, 1973b) proposed a four-factor "theory" of the mediation
of teacher expectancy effects. In this view, four broad groupings of teacher
Representative terms from entire chapter:
interpersonal expectancy