Three-year-olds were initially inclined to trust a deceptive informant regardless of whether she used verbal testimony or another, less practiced means of reference, but their trust in testimony—particularly from a visible informant—was much more robust. These results are important because they demonstrate that children’s willingness to believe what they are told reflects a specific bias to trust testimony, rather than a generic, undifferentiated trust in other people.
We suspect that a specific bias to trust testimony develops out of a generally trusting disposition that would be adaptive in infancy (e.g., Baier, 1986
). Some baseline level of trust may be needed to get language acquisition started (Coady, 1992
), but the specific, highly robust bias to trust testimony could emerge from the accumulation of evidence that what people say is normally true (Hume, 1748/2004
). An advantage of this explanation over one positing that testimony is privileged from the start is that the same learning mechanism can be used to explain why 3-year-olds are so credulous when it comes to pointing, another common, normally veridical social signal (Couillard & Woodward, 1999
). Presumably, with enough reinforcement, children could develop robust expectations about the veridicality of other forms of reference as well (e.g., an arrow).
Veridical testimony is so ubiquitous that a specific bias to trust testimony is likely to emerge quite early in development and to remain a powerful force throughout. For example, Jaswal (in press)
found that 2.5-year-olds repeatedly believed an informant’s account of an event even when it conflicted with what they had just seen and even when believing the account prevented them from obtaining a tasty treat. Although older children can more readily learn to do the opposite of what they are told (e.g., Mascaro & Sperber, 2009
), they also sometimes respond reflexively to verbal information, as vividly demonstrated by their errors on “Simon Says” (Strommen, 1973
). Finally, adults, too, are biased to trust testimony: When cognitive resources are taxed, adults are more likely to misremember as true information that they earlier learned was false than to misremember as false information that they earlier learned was true (Gilbert, Krull, & Malone, 1990
Children in Study 2 were more likely to be misled by a visible speaker than by a disembodied voice, even though the testimony was exactly the same in the two cases. This sensitivity to the presence of a potential teacher is consistent with previous findings (e.g., Baldwin et al., 1996
) and demonstrates that the social aspects of information transmission, including gaze direction and contingency, can play an important role in the uptake (for better or worse) of that information (Csibra & Gergely, 2006
; Tomasello, 1999
). Indeed, if the speaker in the testimony condition of Study 1 or the video condition of Study 2 had been less engaging, the children may not have been as likely to be misled (e.g., Topal et al., 2008
). Also, adults appear to make automatic judgments about trustworthiness based on people’s faces (Todorov & Engell, 2008
), and this raises the possibility that the particular visage of the speaker in the testimony condition of Study 1 and the video condition of Study 2 (the same individual) contributed to the children’s credulity.
It is worth noting that there are some circumstances in which 3-year-olds can discount information from an unreliable source. For example, they prefer testimony from a previously accurate speaker over testimony from a previously inaccurate one (e.g., Corriveau, Meints, & Harris, 2009
). But when faced with a single engaging and confident speaker, they tend to accept what he or she says, sometimes even if that testimony is mildly discrepant from their expectations (Jaswal & Malone, 2007
In summary, although 3-year-olds may be generally inclined to trust other people, their willingness to believe what they are told stems from a specific, highly robust bias to trust testimony. The mechanisms by which children learn to become more skeptical and the sources of individual differences in credulity remain intriguing questions for future work.