Thomas Reid argued that the human default trust in testimony is a gift of nature, which is sustained by two principles that "tally with each other", the propensity to speak the truth, and the tendency to trust what others tell us. Interestingly, he observed an embodied aspect of this trust:
It is the intention of nature, that we should be carried in arms before we are able to walk upon our legs; and it is likewise the intention of nature, that our belief should be guided by the authority and reason of others, before it can be guided by our own reason. The weakness of the infant, and the natural affection of the mother, plainly indicate the former; and the natural credulity of youth, and authority of age, as plainly indicate the latter. The infant, by proper nursing and care, acquires strength to walk without support (1764, Inquiry into the Human Mind, chapt VI, Of Seeing)
Reid's observations point to an intriguing possibility: to what extent is social cognition, such as trust in testimony, influenced by our bodily position, in particular the position we have as helpless infants? The Japanese primatologist Tetsuro Matsuzawa has argued that the supine position (that is, position on the back) of human newborns, has been a decisive factor in the evolution of human social cognition.
Humans and chimpanzees differ quite markedly in how much they trust others. For instance, although both chimpanzees and humans imitate, human children are more prone to overimitation than juvenile chimps, the children, but not the chimps, indiscriminately follow actions by an adult that are reduntant in obtaining a desired result (see e.g., here).