Eugenia Polizzi di Sorrentino

Social networks in primates: smart and tolerant species have more efficient networks

Network optimality has been described in genes, proteins and human communicative networks. In the latter, optimality leads to the efficient transmission of information with a minimum number of connections. Whilst studies show that differences in centrality exist in animal networks with central individuals having higher fitness, network efficiency has never been studied in animal groups. Here we studied 78 groups of primates (24 species). We found that group size and neocortex ratio were correlated with network efficiency. Centralisation (whether several individuals are central in the group) and modularity (how a group is clustered) had opposing effects on network efficiency, showing that tolerant species have more efficient networks. Such network properties affecting individual fitness could be shaped by natural selection. Our results are in accordance with the social brain and cultural intelligence hypotheses, which suggest that the importance of network efficiency and information flow through social learning relates to cognitive abilities.

Between-group hostility affects within-group interactions in tufted capuchin monkeys

Between-group competition has long been thought to be a key factor influencing within-group social dynamics. In humans, it has been suggested that between-group competition may favour the emergence of within-group cooperation. However, between-group competition can also be hypothesized to induce social tension and cause within-group social relationships to deteriorate. So far, little research has focused on these possible effects in animal societies. In this study, we used an experimental set-up to manipulate the opportunity for visual aggressive interactions between two adjacent groups of captive tufted capuchin monkeys, Cebus apella, to examine the group members’ behavioural adjustment in terms of affiliation and aggression. The ‘cooperative hypothesis’ predicted social relationships to be positively reinforced by the visual exposure to the adjacent group to buffer between-group hostility. By contrast, the ‘induced-tension hypothesis’ predicted social relationships to be negatively affected by the visual exposure to the adjacent group because of the higher level of social tension induced by between-group hostility. The experimental manipulation did not produce changes in affiliative behaviours, whereas within-group aggression was higher and the dominance hierarchy steeper when visual aggressive interactions between groups were allowed. Overall, interactions with a neighbouring group caused social relationships to deteriorate and partly confirmed the induced-tension hypothesis.

A mechatronic platform for behavioral analysis on nonhuman primates

In this work we present a new mechatronic platform for measuring behavior of nonhuman primates, allowing high reprogrammability and providing several possibilities of interactions. The platform is the result of a multidisciplinary design process, which has involved bio-engineers, developmental neuroscientists, primatologists, and roboticians to identify its main requirements and specifications. Although such a platform has been designed for the behavioral analysis of capuchin monkeys (Cebus apella), it can be used for behavioral studies on other nonhuman primates and children. First, a state-of-the-art principal approach used in nonhuman primate behavioral studies is reported. Second, the main advantages of the mechatronic approach are presented. In this section, the platform is described in all its parts and the possibility to use it for studies on learning mechanism based on intrinsic motivation discussed. Third, a pilot study on capuchin monkeys is provided and preliminary data are presented and discussed.

What time is it? Coping with expected feeding time in capuchin monkeys

Despite their importance for group-living animals, mechanisms that prevent aggressive escalation have seldom been investigated. Conflict prevention might imply the ability to foresee future needs and the question whether animals have this capacity is still open to debate. A few studies have suggested that animals may be able to use anticipatory strategies of conflict management to decrease stress levels and prevent social tension caused by food competition. None the less, the effectiveness of these supposedly preventive strategies has rarely been investigated, and their cognitive requirements are still unclear. We explored these issues by observing a group of captive capuchin monkeys, Cebus apella, subject to fixed scheduled feeding. We collected data on affiliative and aggressive interactions during three conditions: prefeeding, feeding and control. We found that grooming increased before a predictable competitive situation such as scheduled feeding, and that grooming reduced the risk of aggressive escalation and increased co-feeding during the subsequent feeding period. Therefore, prefeeding grooming served as a conflict prevention mechanism. Nevertheless, capuchin monkeys did not specifically select their prefeeding grooming partners on the basis of the expected benefits in the future competitive situation, suggesting that they were not planning their future behaviour, but were probably responding to the current tense situation.

Oxytocin improves the ability of dogs to follow informative pointing: a neuroemotional hypothesis

It has been suggested that dogs’ ability to comprehend human pointing gestures evolved as a by-product of the socio-emotional changes associated with domestication. Given the large role played by the oxytocin system in socio-emotional processes, it is possible to hypothesize a role for oxytocin in modulating dogs’ socio-communicative skills. Indeed, it has been shown that intranasal oxytocin enhances dogs’ ability to use human pointing cues in an object choice task, a classic paradigm used to assess the ability to follow a pointing gesture. We further tested this hypothesis in another sample of dogs and replicated the above findings. We also provided a novel explanation to the above findings, suggesting that oxytocin released during human–dog interactions increases the positive expectations about human behaviour via emotion and reward processes and thus facilitates the interpretation of pointing as leading to positive events. Given the large and deep homology across mammals in the neural mechanisms involved in emotions, oxytocin could be involved in the acquisition of socio-communicative skills during human typical as well as pathological development.

Exploration and learning in capuchin monkeys (Sapajus spp.): the role of action-outcome contingencies.

Animals have a strong propensity to explore the environment. Spontaneous exploration has a great biological significance since it allows animals to discover and learn the relation between specific behaviours and their consequences. The role of the contingency between action and outcome for learning has been mainly investigated in instrumental learning settings and much less in free exploration contexts. We tested 16 capuchin monkeys (Sapajus spp.) with a mechatronic platform that allowed complex modules to be manipulated and to produce different outcomes. Experimental subjects could manipulate the modules and discover the contingencies between their own specific actions and the outcomes produced (i.e., the opening and lighting of a box). By contrast, Control subjects could operate on the modules, but the outcomes experienced were those performed by their paired Experimental subjects (“yoked-control” paradigm). In the exploration phase, in which no food reward was present, Experimental subjects spent more time on the board and manipulated the modules more than Yoked subjects. Experimental subjects outperformed Yoked subjects in the following test phase, where success required recalling the effective action so to open the box, now baited with food. These findings demonstrate that the opportunity to experience action–outcome contingencies in the absence of extrinsic rewards promotes capuchins’ exploration and facilitates learning processes. Thus, this intrinsically motivated learning represents a powerful mechanism allowing the acquisition of skills and cognitive competence that the individual can later exploit for adaptive purposes.

The “Mechatronic Board”: A Tool to Study Intrinsic Motivations in Humans, Monkeys, and Humanoid Robots

In this chapter the design and fabrication of a new mechatronic platform (called “mechatronic board”) for behavioural analysis of children, non-human primates, and robots are presented and discussed. The platform is the result of a multidisciplinary design approach which merges indications coming from neuroscientists, psychologists, primatologists, roboticists, and bioengineers, with the main goal of studying learning mechanisms driven by intrinsic motivations and curiosity. This chapter firstly introduces the main requirements of the platform, coming from the different needs of the experiments involving the different types of participants. Then, it provides a detailed analysis of the main features of the mechatronic board, focusing on its key aspects which allow the study of intrinsically motivated learning in children and non-human primates. Finally, it shows some preliminary results on curiosity-driven learning coming from pilot experiments involving children, capuchin monkeys, and a computational model of the behaviour of these organisms tested with a humanoid robot (the iCub robot). These experiments investigate the capacity of children, capuchin monkeys, and a computational model implemented on the iCub robot to learn action-outcome contingencies on the basis of intrinsic motivations.

Primates’ Propensity to Explore Objects: How Manual Actions Affect Learning in Children and Capuchin Monkeys

Humans and other animals have a strong propensity to explore the environment. When human infants, as well as other primates, face the opportunity to interact with the environment by manipulating objects, they may discover and learn the contingency between one action and its outcome. Thus, manipulation, as a form of spontaneous exploration, has a great biological significance, since it allows to discover and learn the relationship between action and effect, enabling humans and other animals to plan goal-directed tasks. How do the specific characteristics of the primate’s body influence this process? With its large amount of degrees of freedom, sensors, and nervous terminations, the hand is the main interface with the external world, and it profoundly influences the primates’ interaction with the environment. How does object exploration mediated by manual actions affect the acquisition of problem-solving abilities? To try to answer this question, we experimentally compared how children and capuchin monkeys (Sapajus spp.)—nonhuman primates well known for their manual dexterity and for being curious and highly manipulative—acquire new cause–effect relations through spontaneous manual exploration of a new environment. The experiments were carried out with the mechatronic board, an innovative device specifically designed to allow interspecies comparative research. The board allowed testing whether spontaneous manipulation of objects (not instrumental to achieve any specific goal) improved subjects’ ability to solve a subsequent goal-directed task by retrieving the knowledge learned during previous exploration.