What They Did
The researchers recruited 75 German university students for
a study of the “illusory truth effect,” in which repetition of information
affects perception of its accuracy. Each participant wore electrodes recording
activation of facial muscles involved in furrowing the eyebrows, raising the
eyebrows, and raising the corners of the mouth. They read statements on a
screen, half of which were true and half false.
For the first part of the study, they sorted statements into
assigned categories. Ten minutes later, they rated presented statements as true
or false. Half of the statements were among those that were sorted, and half
were new. One week later, participants performed the statement-rating task with
a combination of new statements and statements from the sorting task that had
not been used in the previous statement-rating task.
The researchers found that participants responded more
quickly to statements they had previously seen, with a much larger difference
between “new” and “old” reaction times after the ten-minute interval than the
one-week interval. Participants were also more likely to rate “old” statements
as true: about 2.5 times more likely after ten minutes and about 1.4 times more
likely after one week. The researchers found greater activation of the eyebrow
furrowing and raising muscles when participants were presented with new
statements after ten minutes but not one week. Eyebrow furrowing muscle
activation was also lower when participants rated statements as true after
either interval. The researchers note that their results provide a
physiological indicator correlated with the illusory truth effect.
Further Exploration
I’m curious about whether the strength of the illusory truth
effect varies between neurotypical and neurodivergent populations. One study
suggested that autistic people are less likely to be influenced by irrelevant
information in making product choices (see https://www.bps.org.uk/research-digest/why-autistic-people-may-be-less-susceptible-marketing-tricks
but also https://kirstykendall.com/autistic-people-commercials/).
I suspect that I’m neurodivergent, and I was surprised that the illusory truth effect
still held in the experimental conditions: the statements were chosen not to be
emotionally evocative and participants were told that some statements would be
true and some false.
I can see how repetition would lead to belief that a
statement is true if it was repeated from multiple sources and personally
relevant – things like being told repeatedly from childhood that vegetables are
healthful. But if random statements like those in the study started appearing
on billboards, I think I would 1) think this was really cool, 2) start
fact-checking the statements after I’d seen them a few times, and 3) get angry
that false statements were being presented as true.
The paper explains
that processing familiar statements takes less cognitive effort, which makes
people more relaxed, which is conflated with a sense of truth. But this also
only happens when familiar and unfamiliar information are mixed. I feel like
having unfamiliar information mixed with familiar information that I thought
was true would make me more likely to trust the unfamiliar information. Of
course, it could also be that I don’t have as much self-knowledge as I think I
do, but that’s a rabbit hole for another day!
Image credit: Kurt Kaiser
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