Human risky choice in a repeated-gambles procedure: an up-linkage replication of Lakshminarayanan, Chen and Santos (2011).

Lakshminarayanan et al. (J Exp Soc Psychol 47: 689-693, 2011) showed that when choice is between variable (risky) and fixed (safe) food amounts with the same expected values, capuchins prefer the safe alternative if choice is framed as a gain, but the risky alternative if it is framed as a loss. These results seem similar to those seen in human prospect-theory tests in choice between variable and fixed gains or losses. Based on this similarity, they interpreted their results as identifying a between-species commonality in cognitive function. In this report, we repeat their experiment with humans as subjects (an up-linkage replication). Whether choices were rewarded with candy or nickels, choice approximated indifference whether framed as gains or losses. Our data mirror those of others who found that when humans make risky choices within a repeated-trials procedure without verbal instruction about outcome likelihoods, preference biases seen in one-shot, language-guided, prospect-theory tests such as Tversky and Kahneman's (Science 211:453-458, 1981) reflection effect may not appear. The disparity between our findings and those of Lakshminarayanan et al. suggests their study does not evidence a cognitive process shared by humans and capuchins.