Implementing long‐term baselines into primate tool‐use studies

Abstract

Studies on primate tool‐use often involve the use of baseline conditions, as they allow for the examination of any differences in the subjects' behavior before and after the introduction of a tool‐use task. While these baseline conditions can be powerful for identifying the relative contributions of individual and social learning for the acquisition of tool‐use behaviors in naïve (usually captive) subjects, many have criticized them for being too short, and not allowing enough time for the behavior to develop spontaneously. Furthermore, some wild tool‐use behaviors such as chimpanzee nut‐cracking require animals to manipulate and familiarize themselves with the materials of the behavior within a “sensitive learning period” before it develops later on in life. One solution to this problem is to implement long‐term baselines, in which, with collaboration with zoological institutions, the materials of the behavior are left in the enclosure for an extended period. The keepers would then be asked not to demonstrate or train the animals in the target behavior, but to report back to the researchers if they observe the behavior emerge during this extended period. Alongside keeper reports, video cameras could be installed in the enclosure to minimize the chance of false negatives and to allow for coding and inter‐rater reliability to be carried out on the videos. These long‐term baselines therefore provide extended enrichment opportunities for the animals, alongside allowing the zoological institution to publicize their involvement with the study and guests to observe animals interacting with different testing apparatuses and tools. Finally, long‐term baselines can provide invaluable insight on the individual and social learning abilities of primates as well as the potential development stages and sensitive learning periods required for specific behaviors.

Naïve, adult, captive chimpanzees do not socially learn how to make and use sharp stone tools

“…However, the fact that all four chimpanzees failed to show the target behaviours after demonstrations suggests that higher levels of enculturation than those possessed by the subjects in this study are required for chimpanzees to copy human knapping and flake-use demonstrations and/or to enable them to innovate these behaviours. However, another possibility is that the chimpanzees in this study may not have had enough time to develop the behaviour, which perhaps may have emerged instead in long-term tests 37 . Indeed, wild chimpanzees often take years to acquire some of their skills, such as nut-cracking 6 , 7 .…”

Leveling the playing field in studying cumulative cultural evolution: Conceptual and methodological advances in nonhuman animal research.

“…For example, self-selection biases may be reduced by testing social groups, by testing for extended periods to overcome potential task monopolization, or by introducing multiple tasks or stimuli so that more than one subject can participate at any given time. Variation in subject rearing histories and experimental experience, if known, can also be controlled for either statistically or in the research design (Bandini, 2021; Neadle et al, 2020; Vale et al, 2021). Implementing comparable testing setups between species will also allow for fairer comparisons (McGuigan et al, 2017; Neldner, 2020).…”

Captive great apes tend to innovate simple tool behaviors quickly

“…Even the helpful suggestion of using motion‐triggered cameras, incurs maintenance costs in addition to the cost of the cameras themselves. Another issue of this long‐term approach is that results (and ensuing debates) could be delayed in time (as acknowledged by Bandini, 2021). Whereas eventual tool innovation in a long‐term baseline would be an important result, it could come years after the start of the experiment (or may not come at all).…”

“…Different approaches can be taken on this regard. Some researchers have proposed that baseline tests should be implemented in the long-term and expanding several years (Bandini, 2021). In an ideal scenario freed of resource-limitations, such approach would allow to account for lifelong possibilities of innovation, resembling what some species encounter in the wild to a certain degree.…”

“…Furthermore, long-term baselines leave unspecified the termination point of the experiment. Although Bandini (2021) suggests some variables that should be taken into consideration when conducting long-term baselines such as the complexity of the task and the existence of a sensitive learning period, no formula exists to calculate an exact termination point. Given these concerns, although we acknowledge the potential value of long-term baselines, we believe that there is a need for a more standardized and accessible experimental approach to investigate tool innovation.…”