How to Write a Persuasive Message

Suppose you must write a message that you want the recipients to believe.
Of course, your message will be true, but that is not necessarily enough for
people to believe that it is true. It is entirely legitimate for you to enlist
cognitive ease to work in your favor, and studies of truth illusions provide
specific suggestions that may help you achieve this goal.
The general principle is that anything you can do to reduce cognitive
strain will help, so you should first maximize legibility. Compare these two
statements:
Adolf Hitler was born in 1892.
Adolf Hitler was born in 1887.
Both are false (Hitler was born in 1889), but experiments have shown that
the first is more likely to be believed. More advice: if your message is to be
printed, use high-quality paper to maximize the contrast between
characters and their background. If you use color, you are more likely to be
believed if your text is printed in bright blue or red than in middling shades
of green, yellow, or pale blue.
If you care about being thought credible and intelligent, do not use
complex language where simpler language will do. My Princeton ton
colleague Danny Oppenheimer refuted a myth prevalent a wo ton colmong
undergraduates about the vocabulary that professors find most impressive.
In an article titled “Consequences of Erudite Vernacular Utilized
Irrespective of Necessity: Problems with Using Long Words Needlessly,”
he showed that couching familiar ideas in pretentious language is taken as
a sign of poor intelligence and low credibility.
In addition to making your message simple, try to make it memorable.
Put your ideas in verse if you can; they will be more likely to be taken as
truth. Participants in a much cited experiment read dozens of unfamiliar
aphorisms, such as:
Woes unite foes.
Little strokes will tumble great oaks.
A fault confessed is half redressed.
Other students read some of the same proverbs transformed into
nonrhyming versions:
Woes unite enemies.
Little strokes will tumble great trees.
A fault admitted is half redressed.
The aphorisms were judged more insightful when they rhymed than when
they did not.
Finally, if you quote a source, choose one with a name that is easy to
pronounce. Participants in an experiment were asked to evaluate the
prospects of fictitious Turkish companies on the basis of reports from two
brokerage firms. For each stock, one of the reports came from an easily
pronounced name (e.g., Artan) and the other report came from a firm with
an unfortunate name (e.g., Taahhut). The reports sometimes disagreed.
The best procedure for the observers would have been to average the two
reports, but this is not what they did. They gave much more weight to the
report from Artan than to the report from Taahhut. Remember that System
2 is lazy and that mental effort is aversive. If possible, the recipients of your
message want to stay away from anything that reminds them of effort,
including a source with a complicated name.
All this is very good advice, but we should not get carried away. Highquality
paper, bright colors, and rhyming or simple language will not be
much help if your message is obviously nonsensical, or if it contradicts
facts that your audience knows to be true. The psychologists who do these
experiments do not believe that people are stupid or infinitely gullible. What
psychologists do believe is that all of us live much of our life guided by the
impressions of System 1—and we often do not know the source of these
impressions. How do you know that a statement is true? If it is strongly
linked by logic or association to other beliefs or preferences you hold, or
comes from a source you trust and like, you will feel a sense of cognitive
ease. The trouble is that there may be other causes for your feeling of ease
—including the quality of the font and the appealing rhythm of the prose—
and you have no simple way of tracing your feelings to their source. This is
the message of figure 5: the sense of ease or strain has multiple causes,
and it is difficult to tease them apart. Difficult, but not impossible. People
can overcome some of the superficial factors that produce illusions of truth
when strongly motivated to do so. On most occasions, however, the lazy
System 2 will adopt the suggestions of System 1 and march on.

Strain and Effort
The symmetry of many associative connections was a dominant theme in
the discussion of associative coherence. As we saw earlier, people who
are made to “smile” or “frown” by sticking a pencil in their mouth or holding
a ball between their furrowed brows are prone to experience the emotions
that frowning and smiling normally express. The same self-reinforcing
reciprocity is found in studies of cognitive ease. On the one hand, cognitive
strain is experienced when the effortful operations of System 2 are
engaged. On the other hand, the experience of cognitive strain, whatever
its source, tends to mobilize System 2, shifting people’s approach to
problems from a casual intuitive mode to a more engaged and analytic
mode.
The bat-and-ball problem was mentioned earlier as a test of people’s
tendency to answer questions with the first idea that comes to their mind,
without checking it. Shane Frederick’s Cognitive Reflection Test consists
of the bat-and-ball problem and two others, all chosen because they evoke
an immediate intuitive answer that is incorrect. The other two items in the
CRT are:
If it takes 5 machines 5 minutes to make 5 widgets, how long
would it take 100 machines to make 100 widgets?
100 minutes OR 5 minutes
In a lake, there is a patch of lily pads. Every day, the patch
doubles in size.
If it takes 48 days for the patch to cover the entire lake, how long
would it take for the patch to cover half of the lake?
24 days OR 47 days
The correct answers to both problems are in a footnote at the bottom of the
page.* The experimenters recruited 40 Princeton students to take the CRT.
Half of them saw the puzzles in a small font in washed-out gray print. The
puzzles were legible, but the font induced cognitive strain. The results tell a
clear story: 90% of the students who saw the CRT in normal font made at
least one mistake in the test, but the proportion dropped to 35% when the
font was barely legible. You read this correctly: performance was better
with the bad font. Cognitive strain, whatever its source, mobilizes System
2, which is more likely to reject the intuitive answer suggested by System
1.