Bonobos and orangutans, but not chimpanzees, flexibly plan for the future in a token-exchange task

Abstract

Non-human animals, including great apes, have been suggested to share some of the skills for planning that humans commonly exhibit. A crucial difference between human and non-human planning may relate to the diversity of domains and needs in which this skill is expressed. Although great apes can save tools for future use, there is little evidence yet that they can also do so in other contexts. To investigate this question further, we presented the apes with a planning token-exchange task that differed from standard tool-use tasks. Additionally, we manipulated the future outcome of the task to investigate planning flexibility. In the Exchange condition, subjects had to collect, save and transport tokens because they would need them 30 min later to exchange them for food with a human, i.e., "bring-back" response. In the Release condition, the collection and transport of tokens were not needed as no exchange took place after 30 min. Out of 13 subjects, eight solved the task at least once in the Exchange condition, with chimpanzees appearing less successful than the other species. Importantly, three individuals showed a clear differential response between conditions by producing more "bring-back" responses in the Exchange than in the Release conditions. Those bonobo and orangutan individuals hence adapted their planning behavior according to changing needs (i.e., they brought tokens back significantly more often when they would need them). Bonobos and orangutans, unlike chimpanzees, planned outside the context of tool-use, thus challenging the idea that planning in these species is purely domain-specific.

What can associative learning do for planning?

“…However, these claims have been contested based on at least two different lines of arguments. First, researchers have raised doubts concerning birds’ general capacity to plan because planning studies in birds typically involve caching specialists performing caching tasks, such as scrub jays ( Aphelocoma californica ), Eurasian jays ( Garrulus glandarius ) and black-capped chickadees ( Poecile atricapillus ) [27,29,30]. These results may be caused by specialized memory repertoires (cf.…”

Parallel overinterpretation of behavior of apes and corvids

“…To test whether birds were planning, as in thinking about the future use of the items in 15 minutes or 17 hours, the experimenters would need to include control conditions that test whether birds choose the bottle caps and stones only when they have a plan for using them. For example, birds should not select these objects when they know there will be no future opportunity to use them (see, for an example, Bourjade, Call, Pele, Maumy, & Dufour, 2014). Alternatively, a condition could be arranged in which birds choose between the bottle tops and the rocks under conditions in which they are informed that only one or the other would be useful in the future.…”

Understanding Language Evolution: Beyond Pan‐Centrism

“…Even after including tasks measuring non‐social domains, many studies still show no clear‐cut differences between genera, and when differences exist, it is not always the case that Pan consistently outperforms the other great ape genera. For instance, chimpanzees outperform orangutans in object permanence and causality tasks but the reverse seems to be true in some problem‐solving tasks . There is, therefore, no compelling evidence that any of the great ape species consistently outclasses all the others in every domain.…”

“…[46] In captivity, where socio-ecological conditions are often virtually equal across great ape genera, Pan does not consistently outperform other great ape genera in social cognition measured either as single tasks, [48][49][50] or as part of a multi-item test battery. [51] Even after including tasks measuring non-social domains, many studies still show no clear-cut differences between genera, [52][53][54][55][56] and when differences exist, [51,57,58] it is not always the case that Pan consistently outperforms the other great ape genera. For instance, chimpanzees outperform orangutans in object permanence and causality tasks [51] but the reverse seems to be true in some problem-solving tasks.…”

“…For instance, chimpanzees outperform orangutans in object permanence and causality tasks [51] but the reverse seems to be true in some problem-solving tasks. [57][58][59] There is, therefore, no compelling evidence that any of the great ape species consistently outclasses all the others in every domain. In fact, one of the few results that does seem consistent and generalizable across studies is that individual variation within species is vast and in some cases as large between individuals of the same species as individuals of different species.…”