On the factors influencing great ape cultural behaviours

From the strange pieces of material covering our feet to the shape of the hair on our head, culture pervades every aspect of the modern human condition. Our culture has changed more in the brief time in which our species, as we recognise it today, has existed than perhaps any of the flora or fauna that co-inhabit this planet of ours. However, the cultures of non-human animals (hereafter: animals) are, arguably, mostly stationary, the mechanisms underlying them and influencing the expression of them are highly debated in the comparative psychology, anthropology, biology and cultural evolutionary literature. This thesis sits at the intersection of these literatures and asks and attempts to answer some questions about the cultures of our closest extant relatives, the non-human great apes (henceforth: apes). For example, can ape cultures emerge without the inclusion of special variants of social learning? What are the social learning capacities of apes (do apes "ape")? Overall, what are the factors influencing ape cultures, and how do these compare to what we know of our own culture. In this thesis, I will build on already existing methodologies, e.g., the Latent Solutions methodology (Tennie & Hedwig, 2009), and apply them in novel ways. In doing so I will target some of the more controversial issues in the aforementioned fields and attempt, using controlled and consistent testing procedures, to add new understanding of culture and social learning in apes to the literature surrounding it

Testing the individual and social learning abilities of task-naïve captive chimpanzees (Pan troglodytes sp.) in a nut-cracking task

Nut-cracking is often cited as one of the most complex behaviours observed in wild chimpanzees. However, the cognitive mechanisms behind its acquisition are still debated. The current null hypothesis is that the form of nut-cracking behaviour relies on variants of social learning, with some researchers arguing, more precisely, that copying variants of social learning mechanisms are necessary. However, to date, very few experiments have directly investigated the potentially sufficient role of individual learning in explaining the behavioural form of nut-cracking. Despite this, the available data provides some evidence for the spontaneous acquisition of nut-cracking by chimpanzees; later group acquisition was then found to be at least facilitated by (unspecified) variants of social learning. The latter findings are in line with both suggested hypotheses, i.e., that copying social learning is required and that other (non-copying) social learning mechanisms are at play. Here we present the first study which focused (initially) on the role of individual learning for the acquisition of the nut-cracking behavioural form in chimpanzees. We tested task-naïve chimpanzees (N = 13) with an extended baseline condition to examine whether the behaviour would emerge spontaneously. After the baseline condition (which was unsuccessful), we tested for the role of social learning by providing social information in a step-wise fashion, culminating in a full action demonstration of nut-cracking by a human demonstrator (this last condition made it possible for the observers to copy all actions underlying the behaviour). Despite the opportunities to individually and/or socially learn nut-cracking, none of the chimpanzees tested here cracked nuts using tools in any of the conditions in our study; thus, providing no conclusive evidence for either competing hypothesis. We conclude that this failure was the product of an interplay of factors, including behavioural conservatism and the existence of a potential sensitive learning period for nut-cracking in chimpanzees. The possibility remains that nut-cracking is a behaviour that chimpanzees can individually learn. However, this behaviour might only be acquired when chimpanzees are still inside their sensitive learning period, and when ecological and developmental conditions allow for it. The possibility remains that nut-cracking is an example of a culture dependent trait in non-human great apes. Recommendations for future research projects to address this question are considered

Food cleaning in gorillas: Social learning is a possibility but not a necessity

Food cleaning is widespread in the animal kingdom, and a recent report confirmed that (amongst other behaviours) wild western lowland gorillas also show food cleaning. The authors of this report conclude that this behaviour, based on its distribution patterns, constitutes a potential candidate for culture. While different conceptualisations of culture exist, some more and some less reliant on behavioural form copying, all of them assign a special role to social learning processes in explaining potentially cultural behaviours. Here we report the results of an experiment that tested to what extent food cleaning behaviour in a group of captive Western lowland gorillas (Gorilla gorilla gorilla) relies on social learning processes. Subjects were provided with clean and dirty apples. When they were provided with dirty apples, all subjects showed evidence of food cleaning in at least 75% of trials. Preferred cleaning techniques differed between individuals, four out of five of subjects expressed a behaviour analogous to that reported in wild conspecifics. Given this occurrence of food cleaning in a culturally unconnected population of gorillas, we conclude that social learning is unlikely to play a central role in the emergence of the food cleaning behavioural form in Western lowland gorillas; instead, placing a greater emphasis on individual learning of food cleaning’s behavioural form

The role of religiosity in adult affective-wellbeing following adverse childhood experiences.

A cross-sectional, online survey based study, analysed via multiple generalised linear mixed models, exploring the impact of religiosity on adult affective-wellbeing following adverse childhood experiences

Food cleaning sequence in an adult female Western lowland gorilla (“Kibara”) cleaning and eating a peeled sand covered apple using the method described by Robbins et al [9]; See S2 File.

<p>Food cleaning sequence in an adult female Western lowland gorilla (“Kibara”) cleaning and eating a peeled sand covered apple using the method described by Robbins et al [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188866#pone.0188866.ref009" target="_blank">9</a>]; See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188866#pone.0188866.s002" target="_blank">S2 File</a>.</p

Effect of Social Learning Biases on Great Ape Imitative Capacities

This is a project that aims to assess the upper capacities of non-human great apes social learning mechanisms. We have developed a task that requires true action copying to complete. In order to facilitate this action copying, which is yet to be identified in non-human great apes, we employ the social learning bias of "conformist transmission"

Methods of cleaning fruit coded, along with description, as provided to independent coders, see S1 File.

<p>Methods of cleaning fruit coded, along with description, as provided to independent coders, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188866#pone.0188866.s001" target="_blank">S1 File</a>.</p

Percentage of dirty apples cleaned <i>before</i> first bite was taken, separated by individual.

<p>Percentage of dirty apples cleaned <i>before</i> first bite was taken, separated by individual.</p