Truth Effect and Truth Judgments

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The truth effect (engl. Truth effect , illusory truth effect , frequency validity effect ; also Validity effect or Reiterationseffekt) describes the phenomenon of cognitive psychology that statements that were previously heard or read, a greater veracity is awarded as such, the be heard for the first time. The truth effect is based on processes of the implicit memory : The actual memory content (here: the statement) cannot be consciously remembered, but leads to its truth content being judged more highly.

Historical Roots of the Truth Effect: The Hasher, Goldstein & Toppino Experiment (1977)

The first investigation into the truth effect was carried out by Lynn Hasher, David Goldstein and Thomas Toppino in 1977: They wanted to find out how people perceive knowledge and suspected that the frequency of hearing or reading a statement contributes to the correctness of it Statement believes. To check this, they presented their 30 student test subjects three times a larger set of statements every two weeks. The statements were designed to be plausible, but at the same time so unknown that most test subjects could not say with certainty whether they were right or wrong (e.g., "The People's Republic of China was founded in 1947"). In fact, half of the statements were true and half were false. The test subjects were given 60 statements at each of the three measurement times. Twenty of them were always the same statements (10 correct and 10 incorrect), the remaining 40 different from measurement time to measurement time. The task of the test subjects was to assess after each statement on a 7-point scale how true they thought it was. The results of the study showed that the statements that were presented at all three measurement times were actually assigned a significantly greater truth content than the statements that were only presented at one of the three measurement times. This shows that the repetition of a statement leads to it being perceived as more true.

Memory processes behind the truth effect

The Spinoza versus Descartes Debate: How Truth is Represented in Memory

How truth and falsehood are represented in memory has preoccupied scholars for several hundred years. The theses of two philosophers from the 17th century are still discussed and examined today: One of these two theses was put forward by Baruch de Spinoza (quoted in Gilbert, Krull, & Malone, 1990) and assumes that a statement heard or read in is understood in a first step and at the same time accepted as true and in a second step, using cognitive resources, it may be checked again for its truthfulness and possibly categorized as false. René Descartes, on the other hand, postulated (quoted in Gilbert et al., 1990) that a statement is initially only represented mentally without an evaluation taking place. The controlled process in which information is assessed as true or false only takes place in a second step. In contrast to Spinoza , Descartes assumes a separation of the processes of understanding and belief, which is referred to as the doctrine of separate mental acts (English "doctrine of separate mental acts").

The Hopi Language Experiment by Gilbert and Colleagues (1990)

Gilbert and colleagues (1990) found evidence of Spinoza's model in their Hopi language experiment when they let test subjects learn a fictional language and provided them with information on the correctness of individual translations. At the same time, the test subjects had to press a key as quickly as possible when a tone sounded. According to Spinoza's model, this interruption should disturb the controlled process of re-checking the statement so that a higher error rate results and the test subjects should remember false statements as true. The results of the study actually showed that the test subjects judged false statements to be true more often if they were disturbed in processing the statement. In this way, Gilbert and colleagues provided empirical support for Spinoza's position, according to which a statement is first understood and accepted and only checked in a second step for its truthfulness with the use of resources.

Further influences on truth judgments: Perceptual fluency

Another factor influencing truth judgments was examined by Rolf Reber and Norbert Schwarz : They tested whether the perceptual fluidity (a sub-category of processing fluid ) of the stimulus material affects the attribution of truth and falsehood. To this end, they presented their test subjects with 32 statements in the form “City A is in country B” (e.g. “Osorno is in Chile”). Half of these statements were true and half were false. Reber and Schwarz also varied the color in which these statements were presented, and thus the perceptual fluidity: some of the test subjects saw the statements in green and yellow (difficult to recognize and therefore poor perceptual fluidity), another part of the test subjects saw them in green and light blue color (moderately recognizable, medium perceptual fluid) and a third part of the test persons in dark blue and red color (well recognizable, high perceptual fluid; the colors were tested in a preliminary test for their suitability as an indicator for perceptual fluid). The test subjects' task was to decide whether each statement was true or false. The results showed that statements that were written in easily recognizable color (e.g. red) were rated as significantly more true than statements that were written in a less easily recognizable color (e.g. yellow). Reber and Schwarz (1999) were able to show that judgments of truth can also be influenced independently of the frequency of presentation (see truth effect). Lev-Ari and Keysar (2010) were even able to show that people with an accent (e.g. immigrants) are judged to be less credible by native speakers, since the speaker's accent reduces the perceptual fluency of what is heard.

Literature and Sources

  1. ^ C. Hackett Renner: Validity effect. In: RF Pohl (Ed.): Cognitive illusions. Hove, UK: Psychology Press, 2004, pp. 201-213.
  2. ↑ Hasher, L., Goldstein, D., & Toppino, T. (1977). Frequency and the Conference of Referential Validity. Journal of Verbal Learning and Verbal Behavior, 16, 107-112.
  3. ↑ Gilbert, DT, Krull, DS, & Malone, PS (1990). Unbelieving the unbelievable: Some problems in the rejection of false information. Journal of Personality and Social Psychology, 59, 601-613.
  4. ↑ Gilbert, DT, Tafarodi, RW, & Malone, PS (1993). You can't believe everything you read. Journal of Personality and Social Psychology, 65, 221-233.
  5. ^ Reber, R., & Schwarz, N. (1999). Effects of Perceptual Fluency on Judgments of Truth. Consciousness and Cognition, 8, 338-342.
  6. ^ Lev-Ari, S., & Keysar, B. (2010). Why don't believe non-native speakers? The influence of accent on credibility. Journal of Experimental Social Psychology, 46, 1093-1096.