The Truth Effect

Another line of research under the header “truth effect” deals with a kind of rightness at the very core of the present thesis: truth. The truth effect describes the heightened tendency to judge a statement as (more likely) true as a consequence of manipulating various variables. Importantly, most of this work tests the truth effect in relation to ambiguous statements such as “the zipper was invented in Norway”²⁰⁹, i.e. the judging subject does not have definite information (e.g. knowledge) of the truth value of the statements. What are the variables that exert a truth effect? The most prominent and reliable one is repetition. Subjects rate statements they have been previously exposed to as more likely true (Hasher et al. 1977; Arkes, Boehm, et al. 1991; for a review see Dechˆene et al. 2010).

This effect is well documented and robust across many experimental variations: it occurs for statements that are 1) read (Schwartz 1982) or heard (Hasher et al. 1977; Begg, Anas, et al. 1992); 2) known to be repeated (Bacon 1979; Nadarevic and Aßfalg 2017); 3) a matter of general knowledge (Hasher et al. 1977), trivia (Bacon 1979) or opinion (Arkes, Hackett, et al. 1989); 4) repeated minutes, weeks or months apart (Brown and Nix 1996;

208In fact, one can argue that the detection of semantic coherence is a precursor for the detection of coherence between the elements of a proposition (meaningfulness) which is, in turn, a precursor for the detection of coherence between propositions that are specifically given (logical validity) or between a specifically given proposition and internally stored (and currently activated) propositions (believability) (cf. DeLong et al. 2005; ¨Ollinger and von M¨uller 2017). I will come back to this point in chapter 6.

209This example is taken from Dechˆene et al. 2010, p. 238. According to the authors the zipper was actually invented in Switzerland and thus the statement in the main text is false.

Nadarevic and Erdfelder 2014); 5) are asked to be truth-judged repeatedly (Hasher et al. 1977) or only upon final presentation (Schwartz 1982; Nadarevic and Erdfelder 2014, experiment 2); 6) repeated verbatim or paraphrased (Silva, Garcia-Marques, and Reber 2017); 7) mixed (Dechˆene et al. 2009) or not mixed (Garcia-Marques, Silva, Mello, and Hansen 2019) with unrepeated statements. Additionally, similarly to the truth effect in relation to paraphrases, people tend to judge statements that contradict a previously presented statement as more likely false (“falsity effect”) than unrepeated statements (Bacon 1979), implying that a truth effect has occurred for the previously presented statement. This even holds if the previously presented sentence and the “repeated”

contradiction only differ with respect to a single (crucial) word such as “Crocodiles sleep with the eyes open” and “Crocodiles sleep with the eyes closed” (Garcia-Marques, Silva, Reber, et al. 2015; Silva, Garcia-Marques, and Reber 2017).²¹⁰

In a similar fashion, subjects tend to judge statements as more likely true or false if pre-viously exposed to related (but differing) statements which support or undermine the presented statement (Ozubko and Fugelsang 2011). Relatedly, subjects judge statements more likely true if they were previously only exposed to parts of them or to conceptu-ally related elements, e.g. the topic of the presented statement (Begg, Armour, et al.

1985, experiment 1-2). Interestingly, the repetition-induced truth effect appears nei-ther affected by a subject’s explicit motivation to arrive at an accurate truth judgment (Garcia-Marques, Silva, and Mello 2016), nor by individual differences in epistemically relevant traits such as a subject’s general intelligence (“cognitive ability”), preference for certainty (“need for cognitive closure”) or reliance on “intuitive” versus analytical thinking (“cognitive style”) (De keersmaecker et al. 2019). Furthermore, as mentioned earlier, it has been long assumed that the repetition-induced truth effect only occurs for ambiguous statements. Against this background, Dechˆene and colleagues note:

Overall, the truth effect appears to be very robust. The only constraint seems to be that the statements have to be ambiguous, that is, participants have to be uncertain about their truth status because otherwise the statements’

truthfulness will be judged on the basis of their knowledge (Dechˆene et al.

2010, p. 239).

210Surprisingly, the same authors found that while the falsity effect with contradictory statements could be observed a few minutes after initial statement presentation, it waned after a week. In fact, after one week, the falsity effect transformed into a truth effect: the contradictory statements were perceived as more likely true than new statements. In another context this phenomenon has been called the

“sleeper effect”. “According to this effect, when people receive a communication associated with a discounting cue, such as a noncredible source, they are less persuaded immediately after exposure than they are later in time” (Kumkale and Albarrac´ın 2004, p. 143).

More recent findings, however, cast doubt on this assumption. In fact, some weaker evidence was already around for a while. For instance, Begg, Anas, et al. 1992, Brown and Nix 1996 and, more recently, Henkel and Mattson 2011 presented statements that were paired with sources declared reliable or unreliable by the experimenters. Yet this did not significantly affect the truth effect for repeated statements that were paired with unreliable sources. Memorizing and recollecting sources, however, tend to be difficult and error-prone cognitive tasks (Mitchell and Johnson 2000). This is especially true if the encoded information lacks relevance to the subject: Source monitoring “involves a processing cost which is likely to be kept to a bare minimum when the information communicated is of no possible relevance to oneself” (Sperber, Cl´ement, et al. 2010, p. 363).

However, more recently and forcefully, Fazio, Brashier, et al. 2015 demonstrated that participants give higher truth ratings to repeated statements, even though they seem to possess actual knowledge that contradicts the statements. In the same vein, Unkelbach and Greifeneder 2018 found that even providing 100% reliable advice on the actual truth of a repeated statementduring the judgment modulated but did not eliminate the truth effect. At first glance, this appears alarming. On second thought, however, it is perhaps not all too surprising: One can and often should be willing to question what one or others appear to know. After all, “knowledge” is fallible and should be open to new evidence.²¹¹

Now, whatever happens during the presentation of a repeated statement, might con-stitute new evidence that may or may not conflict with the evidence coming from e.g.

one’s own beliefs or from testimony.²¹² An integration of this conflicting evidence with other information one possesses would produce exactly the observed results: a repetition-induced truth effect tempered but not eliminated by other informational sources. What we see is that our judgment is influenced by various sources of evidence and not by either one or another (cf. ibid.). The finding that knowledge does not eliminate the truth effect indicates that if we take ourselves to possess knowledge about something, we do rely on

211In general, from a subjective point of view, it is difficult if not impossible to be aware ofknowing anything since, ultimately, reality has to comply. This is the basic lesson of epistemic scepticism.

Subjectively and objectively well justified beliefs can justify the subject inbelieving and claiming that she knows. Ultimately, however, these beliefs might turn out to be false and thus fall short of being knowledge.

212In the case of the repetition-induced truth effect, whatever is brought about by repetition, might not constitute evidence if one assumes that repetition does not correlate with truth. This latter assump-tion might be ecologically quesassump-tionable, however (Unkelbach 2007, p. 229; Reber and Unkelbach 2010;

Herzog and Hertwig 2013). More on this later.