Source
Factors
One
important factor in persuasion is the nature of the source of
a message. I will discuss three source factors: expertise,
trustworthiness, and attractiveness. In general, we are
naturally more likely to accept the statements of an expert
than a non-expert. The cognitive response model posits that
when auditors believe the source of a message is an expert,
they have less motivation to scrutinize (develop counter
arguments to) messages attributed to that source. Fewer
unfavorable thoughts, in turn, should result in more attitude
change (with counter-attitudinal messages). On the other hand,
receivers should be more motivated to think critically about
messages from apparently non-expert sources and therefore
produce more counter arguments, reducing persuasion from such
sources (see Benoit,
1991; Gillig & Greenwald,
1974; Hass,
1981; Perloff & Brock,
1980).
Thus, expert sources can reduce the number of
unfavorable thoughts as we defer to the knowledge we assume an
expert possesses.
Research also reveals that expertise influences persuasion
only if the source is identified before the message,
which suggests that credibility influences persuasion by
altering message processing or elaboration (O’Keefe,
1987;
Ward & McGinnies, 1974). Research found that when an
audience was told the source was an expert after
listening to the message, that information did not increase
persuasion. Only if an expert source is identified before
a message does expertise help persuasion. Similarly, some
receivers were told the source was not an expert after
the message. That did not reduce persuasion. However, when
listeners were told that the source was a non-expert before
the message, it did reduce persuasion.
This very strongly suggests that knowledge that the source is
an expert (or a non-expert) influences the way we listen to a
message. Source expertise operates by influencing our
cognitive responses to the message. Once the message is over,
we have already had our cognitive responses, and knowledge
about the source’s expertise, or lack of expertise, is too
late to make a difference. In other words, knowing that the
source is an expert decreases our motivation to engage
in central processing. The expertise reassures us, and we do
not believe we must be critical listeners. However, knowledge
that the source is a non-expert increases our motivation
to engage in central processing. We are suspicious and more
likely to carefully scrutinize the messages of non-experts.
Not surprisingly, research finds that credibility appeals,
which are often peripheral rather than central cues, are more
likely to influence attitude change on uninvolving than
involving topics (Chaiken,
1980; Petty, Cacioppo, &
Goldman, 1981; Petty, Cacioppo & Schumann,
1983). Highly
involved listeners really care about the topic. The subject of
the message is really important to them. Therefore, highly
involved receivers are likely to think carefully about the
message regardless of who it is from. Knowledge that the
source is an expert is unlikely to decrease the motivation of
a highly involved listener. Thus, like other peripheral cues,
source expertise is likely to have more influence on
uninvolved than involved receivers.
Another aspect of sources is their trustworthiness. Some
sources seem to be biased while others are objective. A
spokesperson for the NRA is likely to appear biased on the
issue of gun control. This does not mean that he or she
is certain to lie or distort the facts. However, we naturally
expect most individuals will “put his or her best foot
forward,” focusing on the ideas that help them rather than
on the ideas that hurt them. There is also a third kind of
source called “reluctant testimony,” in which a source
gives evidence against his or her own interest. One
study told some subjects that a prosecutors was in favor of
stricter sentencing for criminals. Other subjects were told
that a prosecutor was in favor of more lenient sentencing. We
would expect most prosecutors to be strict, so the first case
(prosecutor for stricter sentencing) is an example of biased
testimony, while the second case (prosecutor for lighter
sentencing) is an example of reluctant testimony.
Benoit and Kennedy (1999) made certain that subjects’
perceived the expertise of these sources to be equal, and then
varied whether they were thought to be biased, objective, or
reluctant. Biased sources were seen as less trustworthy and
produced more unfavorable and fewer favorable thoughts. They
were also less persuasive. Both objective and reluctant
sources were viewed as more trustworthy (than biased ones),
produced fewer unfavorable and more favorable thoughts, and
were more persuasive. There was no difference between
objective and reluctant sources: They were equally effective
in this study.
Here, trustworthiness does not seem to influence motivation,
because there was no difference in the total number of
thoughts between these three kinds of sources. Rather,
trustworthiness seems to influence the kind of
thoughts. The sources that listeners trusted (objective and
reluctant) produced more favorable and fewer unfavorable
thoughts; the source that receivers did not trust (biased)
produced fewer favorable and more unfavorable thoughts. So,
persuaders would be well-advised to try to avoid appearing
biased and untrustworthy.
Another characteristic of sources is their attractiveness.
Research has shown that physically attractive sources are
persuasive (Berscheid &
Walster, 1974; Eagly & Chaiken,
1975; Shavitt, Swan, Lowrey, & Wanke,
1994).
Attractiveness should generally operate as a peripheral cue.
For example, Mills and
Harvey
(1972)
report that, unlike expert sources, attractive sources
are just as persuasive when identified after as before
the message. Furthermore,
Benoit (1987)
found that attractive
sources did not produce significant attitude change on an
involving topic . Thus, attractiveness effects, like expertise
and argument quantity effects, should be more prominent on
uninvolving than involving topics.
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