1 2 3 Negatively-Biased Credulity and the Cultural Evolution of Beliefs 4 5 6 7 8 Daniel M.T. Fessler,1* Anne C. Pisor,2 and Carlos David Navarrete3 9 10 1 Department of Anthropology and Center for Behavior, Evolution, and Culture 11 University of California, Los Angeles 12 Los Angeles, CA 90095-1553 USA 13 14 2 Department of Anthropology 15 University of California, Santa Barbara 16 Santa Barbara, CA 93106-3210 USA 17 18 3 Department of Psychology 19 Michigan State University 20 East Lansing, MI 48824-1116 USA 21 22 23 * To whom correspondence should be addressed: E-mail:
[email protected] 24 25 26 27 PAPER ACCEPTED FOR PUBLICATION IN PLOS ONE, MARCH 24, 2014 28 1 29 Abstract 30 The functions of cultural beliefs are often opaque to those who hold them. Accordingly, to 31 benefit from cultural evolution’s ability to solve complex adaptive problems, learners must be 32 credulous. However, credulity entails costs, including susceptibility to exploitation, and effort 33 wasted due to false beliefs. One determinant of the optimal level of credulity is the ratio between 34 the costs of two types of errors: erroneous incredulity (failing to believe information that is true) 35 and erroneous credulity (believing information that is false). This ratio can be expected to be 36 asymmetric when information concerns hazards, as the costs of erroneous incredulity will, on 37 average, exceed the costs of erroneous credulity; no equivalent asymmetry characterizes 38 information concerning benefits. Natural selection can therefore be expected to have crafted 39 learners’ minds so as to be more credulous toward information concerning hazards.