Behavioral conservatism is linked to complexity of behavior in chimpanzees (<i>Pan troglodytes</i>):implications for cognition and cumulative culture

Cumulative culture is rare, if not altogether absent in nonhuman species. At the foundation of cumulative learning is the ability to modify, relinquish, or build upon previous behaviors flexibly to make them more productive or efficient. Within the primate literature, a failure to optimize solutions in this way is often proposed to derive from low-fidelity copying of witnessed behaviors, suboptimal social learning heuristics, or a lack of relevant sociocognitive adaptations. However, humans can also be markedly inflexible in their behaviors, perseverating with, or becoming fixated on, outdated or inappropriate responses. Humans show differential patterns of flexibility as a function of cognitive load, exhibiting difficulties with inhibiting suboptimal behaviors when there are high demands on working memory. We present a series of studies on captive chimpanzees that indicate that behavioral conservatism in apes may be underlain by similar constraints: Chimpanzees showed relatively little conservatism when behavioral optimization involved the inhibition of a well-established but simple solution, or the addition of a simple modification to a well-established but complex solution. In contrast, when behavioral optimization involved the inhibition of a well-established but complex solution, chimpanzees showed evidence of conservatism. We propose that conservatism is linked to behavioral complexity, potentially mediated by cognitive resource availability, and may be an important factor in the evolution of cumulative culture.</p

The NAD(P)H oxidase homolog Nox4 modulates insulin-stimulated generation of H\u3csub\u3e2\u3c/sub\u3e0\u3csub\u3e2\u3c/sub\u3e and plays an integral role in insulin signal transduction

Insulin stimulation of target cells elicits a burst of H2O2 that enhances tyrosine phosphorylation of the insulin receptor and its cellular substrate proteins as well as distal signaling events in the insulin action cascade. The molecular mechanism coupling the insulin receptor with the cellular oxidant-generating apparatus has not been elucidated. Using reverse transcription-PCR and Northern blot analyses, we found that Nox4, a homolog of gp91phox, the phagocytic NAD(P)H oxidase catalytic subunit, is prominently expressed in insulin-sensitive adipose cells. Adenovirus-mediated expression of Nox4 deletion constructs lacking NAD(P)H or FAD/NAD(P)H cofactor binding domains acted in a dominant-negative fashion in differentiated 3T3-L1 adipocytes and attenuated insulin-stimulated H2O2 generation, insulin receptor (IR) and IRS-1 tyrosine phosphorylation, activation of downstream serine kinases, and glucose uptake. Transfection of specific small interfering RNA oligonucleotides reduced Nox4 protein abundance and also inhibited the insulin signaling cascade. Overexpression of Nox4 also significantly reversed the inhibition of insulin-stimulated IR tyrosine phosphorylation induced by coexpression of PTP1B by inhibiting PTP1B catalytic activity. These data suggest that Nox4 provides a novel link between the IR and the generation of cellular reactive oxygen species that enhance insulin signal transduction, at least in part via the oxidative inhibition of cellular protein-tyrosine phosphatases (PTPases), including PTP1B, a PTPase that has been previously implicated in the regulation of insulin action

Innovative multi-material tool use in the pant-hoot display of a chimpanzee

‘Pant-hoot displays’ are a species-typical, multi-modal communicative behaviour in chimpanzees in which pant-hoot vocalisations are combined with varied behavioural displays. In both captivity and the wild, individuals commonly incorporate striking or throwing elements of their environment into these displays. In this case study, we present five videos of an unenculturated, captive, adult male chimpanzee combining a large rubber feeding tub with excelsior (wood wool) in a multi-step process, which was then integrated into the subject’s pant-hoot displays as a percussive tool or ‘instrument’. During the construction process, the subject demonstrated an understanding of the relevant properties of these materials, ‘repairing’ the tub to be a more functional drum when necessary. We supplement these videos with a survey of care staff from the study site for additional detail and context. Although care must be taken in generalising data from a single individual, the behaviour reported here hints at three intriguing features of chimpanzee communicative cognition: (1) it suggests a degree of voluntary control over vocal production, (2) it is a so-far unique example of compound tool innovation and use in communicative behaviour and (3) it may represent an example of forward planning in communicative behaviour. Each of these would represent hitherto undocumented dimensions of flexibility in chimpanzee communication, mapping fertile ground for future research

Chimpanzees prioritise social information over pre-existing behaviours in a group context but not in dyads

Funding: John Templeton Foundation (US) (40128).How animal communities arrive at homogeneous behavioural preferences is a central question for studies of cultural evolution. Here, we investigated whether chimpanzees (Pan troglodytes) would relinquish a pre-existing behaviour to adopt an alternative demonstrated by an overwhelming majority of group mates; in other words, whether chimpanzees behave in a conformist manner. In each of five groups of chimpanzees (N = 37), one individual was trained on one method of opening a two-action puzzle box to obtain food, while the remaining individuals learned the alternative method. Over 5 h of open access to the apparatus in a group context, it was found that 4/5 ‘minority’ individuals explored the majority method and three of these used this new method in the majority of trials. Those that switched did so after observing only a small subset of their group, thereby not matching conventional definitions of conformity. In a further ‘Dyad’ condition, six pairs of chimpanzees were trained on alternative methods and then given access to the task together. Only one of these individuals ever switched method. The number of observations that individuals in the minority and Dyad individuals made of their untrained method was not found to influence whether or not they themselves switched to use it. In a final ‘Asocial’ condition, individuals (N = 10) did not receive social information and did not deviate from their first-learned method. We argue that these results demonstrate an important influence of social context upon prioritisation of social information over pre-existing methods, which can result in group homogeneity of behaviour.Publisher PDFPeer reviewe

Chimpanzees’ Socially Maintained Food Preferences Indicate both Conservatism and Conformity

Chimpanzees remain fixed on a single strategy, even if a novel, more efficient, strategy is introduced. Previous studies reporting such findings have incorporated paradigms in which chimpanzees learn one behavioural method and then are shown a new one that the chimpanzees invariably do not adopt. This study provides the first evidence that chimpanzees show such conservatism even when the new method employs the identical required behaviour as the first, but for a different reward. Groups of chimpanzees could choose to exchange one of two inedible tokens; one was rewarded with a highly preferred food (grape) and the other with a less preferred food (carrot). Individuals first observed a model chimpanzee from their social group trained to choose one of the two types of tokens. In one group, this token earned a carrot, while in the other, control, group the token earned a grape. In both groups, chimpanzees conformed to the trained model’s choice. This was especially striking for those gaining the pieces of carrot; the less favoured reward. This resulted in a population-level trend of food choices, even when counter to their original, individual, preferences. Moreover, the chimpanzees’ food preferences did not change over time, demonstrating that these results were not due to a simple shift in preferences. We discuss social factors apparent in the interactions and suggest that, despite seeming to be inefficient, in chimpanzees, conformity may benefit them, possibly by assisting with the maintenance of group relations

The Ontogeny of Social Comparisons by Rhesus Macaques (Macaca mulatta)

This longitudinal study investigated the development of social contrast-negative responses to inequitable rewards-in rhesus macaques (Macaca mulatta). Although responses to inequity by humans appear universal, this is something that develops with age. Infants first recognize inequity when around 18 months old and respond to it only when they are around 3 years old. To date, however, there have been no studies of the ontogeny of the inequity response in any species other than humans. To address this, we used an exchange paradigm, in which 10 pairs of rhesus monkeys had to exchange inedible tokens with the experimenter to get food rewards that differed in quality depending on the condition. All subjects were tested first when they were an average of 17 months old and a subset, of four pairs, was tested again a year later. Subjects responded negatively to contrast-recognizing a disparity in expected, as compared to, received rewards-based on both social and individual comparisons at the older age, but not at the younger age. Similar to humans, rhesus showed a developmental trajectory to social comparison, providing the first evidence for the ontogeny of this response in a non-human species

When Given the Opportunity, Chimpanzees Maximize Personal Gain Rather than “Level the Playing Field”

We provided chimpanzees (Pan troglodytes) with the ability to improve the quality of food rewards they received in a dyadic test of inequity.We were interested to see if this provision influenced their responses and, if so, whether it was mediated by a social partner’s outcomes. We tested eight dyads using an exchange paradigm in which, depending on the condition, the chimpanzees were rewarded with either high-value (a grape) or low-value (a piece of celery) food rewards for each completed exchange. We included four conditions. In the first, “Different” condition, the subject received different, less-preferred, rewards than their partner for each exchange made (a test of inequity). In the “Unavailable” condition, high-value rewards were shown, but not given, to both chimpanzees prior to each exchange and the chimpanzees were rewarded equally with low-value rewards (a test of individual contrast). The final two conditions created equity. In these High-value and Low-value “Same” conditions both chimpanzees received the same food rewards for each exchange.Within each condition, the chimpanzees first completed ten trials in the Baseline Phase, in which the experimenter determined the rewards they received, and then ten trials in the Test Phase. In the Test Phase, the chimpanzees could exchange tokens through the aperture of a small wooden picture frame hung on their cage mesh in order to receive the high-value reward. Thus, in the Test Phase, the chimpanzees were provided with an opportunity to improve the quality of the rewards they received, either absolutely or relative to what their partner received. The chimpanzees responded in a targeted manner; in the Test Phase they attempted to maximize their returns in all conditions in which they had received low-value rewards during the Baseline Phase. Thus, the chimpanzees were apparently motivated to increase their reward regardless of their partners’, but they only used the mechanism provided when it afforded the opportunity for them to increase their rewards.We also found evidence that the chimpanzees’ responses were enhanced by social facilitation. Specifically, the chimpanzees were more likely to exchange their tokens through the frame when their test partner also did so, even in circumstances in which their reward value could not be improved. Our paradigm provided the chimpanzees with the possibility to improve the quality of rewards they received in the Test Phase. We found that refusals – to exchange tokens or to eat rewards – decreased significantly in the Test Phase compared to the Baseline Phase, where no such opportunity for improvement of outcomes existed. Thus, the chimpanzees participated more when they could improve the rewards they received

Characterisation and application of a bovine U6 promoter for expression of short hairpin RNAs

BackgroundThe use of small interfering RNA (siRNA) molecules in animals to achieve double-stranded RNA-mediated interference (RNAi) has recently emerged as a powerful method of sequence-specific gene knockdown. As DNA-based expression of short hairpin RNA (shRNA) for RNAi may offer some advantages over chemical and in vitro synthesised siRNA, a number of vectors for expression of shRNA have been developed. These often feature polymerase III (pol. III) promoters of either mouse or human origin.ResultsTo develop a shRNA expression vector specifically for bovine RNAi applications, we identified and characterised a novel bovine U6 small nuclear RNA (snRNA) promoter from bovine sequence data. This promoter is the putative bovine homologue of the human U6-8 snRNA promoter, and features a number of functional sequence elements that are characteristic of these types of pol. III promoters. A PCR based cloning strategy was used to incorporate this promoter sequence into plasmid vectors along with shRNA sequences for RNAi. The promoter was then used to express shRNAs, which resulted in the efficient knockdown of an exogenous reporter gene and an endogenous bovine gene.ConclusionWe have mined data from the bovine genome sequencing project to identify a functional bovine U6 promoter and used the promoter sequence to construct a shRNA expression vector. The use of this native bovine promoter in shRNA expression is an important component of our future development of RNAi therapeutic and transgenic applications in bovine species.<br /

Chimpanzees demonstrate individual differences in social information use

Studies of transmission biases in social learning have greatly informed our understanding of how behaviour patterns may diffuse through animal populations, yet within-species inter-individual variation in social information use has received little attention and remains poorly understood. We have addressed this question by examining individual performances across multiple experiments with the same population of primates. We compiled a dataset spanning 16 social learning studies (26 experimental conditions) carried out at the same study site over a 12-year period, incorporating a total of 167 chimpanzees. We applied a binary scoring system to code each participant’s performance in each study according to whether they demonstrated evidence of using social information from conspecifics to solve the experimental task or not (Social Information Score—‘SIS’). Bayesian binomial mixed effects models were then used to estimate the extent to which individual differences influenced SIS, together with any effects of sex, rearing history, age, prior involvement in research and task type on SIS. An estimate of repeatability found that approximately half of the variance in SIS was accounted for by individual identity, indicating that individual differences play a critical role in the social learning behaviour of chimpanzees. According to the model that best fit the data, females were, depending on their rearing history, 15–24% more likely to use social information to solve experimental tasks than males. However, there was no strong evidence of an effect of age or research experience, and pedigree records indicated that SIS was not a strongly heritable trait. Our study offers a novel, transferable method for the study of individual differences in social learning