Bonobo, chimpanzee or gambler?

By Dave Armstrong - 11 Feb 2015 9:43:0 GMT
Bonobo, chimpanzee or gambler?

The bonobo family is typically affectionate and shows several different behavioural traits compared to the chimpanzee, but whether they are closer to our own species is almost impossible to judge. Here, they turn out as equivalent to chimpanzees, at a very simple level.Bonobo image; Credit: © Shutterstock

Controversy always rages around the position of the bonobo as a very advanced chimpanzee that exhibits human-like character. More likely, the 3 close relatives evolved independently from other hominins as we described in Aping Human Ecologies! Christopher Krupenye, Alexandra G. Rosati and Brian Hare have contrived to resolve some risk-related issues that may shed light on these 3 species. They hail from Duke and Yale Universities, in the US and work as anthropologists and psychologists, for their sins.

The subject of their studies was framing effects, the decisions we make where we assess losses as different from where we gain. 40 Pan paniscus and P. troglodytes were given simple tasks needing no previous experience. One framed option was a preferred food (fruit) item, with the alternative being constant amounts of intermediately-preferred food (peanuts.) Firstly, one or two pieces of preferred food were proffered as a positive gain event. For a loss condition, the negativity consisted of a view of 2 pieces of food, after which sometimes only one was offered.

The idea is that the pay-offs were the same, but the apes chose the positive framed option more often in 59.6% of the trials. Males chose the framed option more frequently than the females did. The experiments seemed to indicate that human economic bias could be shared through common descent with other primates. Our biases are not always rational, but have influence on our judgement and decision-making. Gambling is a perfect example, where positive ideas about winning often influence to obvious statistics.

The likelihood is that framing requires human cultural experience, OR that we inherit this tendency from ancestors, perhaps even more distant than our near-relatives. Capuchins, Cebus apella prefer to trade a token with an experimenter who offers a smaller amount of food with occasional bonus food to another experimenter who offered more, but sometimes reduced the amount. Even starlings, Sternus vulgaris like to take risks in attempting to acquire gains. These experiments needed extensive training however. And that may well have influenced the decision-making.

The 23 chimpanzees were from Tchimpounga Sanctuary in the Republic of Congo and the 17 bonobos were from Lola ya Bonobo Sanctuary in the Democratic Republic of Congo. Both species performed in the same manner, giving very similar results. Previous studies have shown the species exhibiting differences in rsik preferences. The authors believe this infers some cognition relevant to their socio-ecologies. To investigate this further would require checking the reflection effect. This involves the individual taking more risk in an attempt to avoid certain losses than when attempting to acquire gains.

As for the male risk-taking, they showed a stronger response to framing. Humans have not been proved to act in similar ways, but men may respond to negative framing when making decisions about resources and also could show different emotional reactions in this context. The research can be read in the latest Biology Letters of the Proc.Roy.Soc.B as Bonobos and chimpanzees exhibit human-like framing effects