Framing the debate on human-like framing effects in bonobos and chimpanzees: a comment on Krupenye et al. (2015).

2016 Framing the debate on human-like framing effects in bonobos and chimpanzees: a comment on Krupenye et al. Recently, Krupenye, Rosati & Hare (KRH henceforth) reported that bonobos and chimpanzees show 'human-like framing effects' in a food choice task [1]. Chimpanzees and bonobos could choose between a 'framed' option of fruit and an alternative option of peanuts (matched in expected value to the framed option). Apes saw either one fruit piece to which one piece was added with p ¼ 0.5 probability (gain frame) or two fruit pieces from which one piece was subtracted with p ¼ 0.5 probability (loss frame). Apes chose the framed option more often in a gain frame than in a loss frame (though this effect was strongest in male apes). 1 KRH conclude that ". . .both of humans' closest relatives exhibit human-like framing effects.. . " and that this bias may be the product of ". . .shared ancestry between humans, non-human apes and perhaps other species as well. " (p. 3). KRH claim that they investigated attribute framing: ". . .the current study focused on the apes' preference for an option framed positively (as a gain) versus negatively (as a loss)—or attribute framing—not how framing impacts their risk preferences. " (p. 3). In the human literature, attribute framing is demonstrated by asking participants to evaluate an object with an attribute that is framed positively in one group and framed negatively in another group (e.g. meat is 80% fat or 20% lean; [3]). It is unclear whether KRH's tasks represents a non-verbal approximation of an attribute framing task as they gave apes a choice between a framed option and a un-framed alternative and, moreover, used a variable pay-off for the framed option (adding or subtracting food 50% of the time, respectively). In fact, KRH's study is metho-dologically very similar to previous studies on framing of risky decisions ([4,5]—though these studies framed both, the risky and the safe option) and some recent paradigms in human risky choice [6]. We therefore suggest to evaluate KRH's findings in relation to human and animal studies on risky decision-making. In the human literature, most participants choose a risky option over a safe option with equal expected value when pay-offs for both options are described as losses (e.g. lives lost), but exhibit a preference reversal when pay-offs are described as gains (e.g. lives saved) [7]. However, more recent work has …