Object grasping and manipulation in capuchin monkeys (genera Cebus and Sapajus)

The abilities to perform skilled hand movements and to manipulate objects dexterously are landmarks in the evolution of primates. The study of how primates use their hands to grasp and manipulate objects in accordance with their needs sheds light on how these species are physically and mentally equipped to deal with the problems they encounter in their daily life. We report data on capuchin monkeys, highly manipulative platyrrhine species that usually spend a great deal of time in active manipulation to search for food and to prepare it for ingestion. Our aim is to provide an overview of current knowledge on the ability of capuchins to grasp and manipulate objects, with a special focus on how these species express their cognitive potential through manual behaviour. Data on the ability of capuchins to move their hands and on the neural correlates sustaining their actions are reported, as are findings on the manipulative ability of capuchins to anticipate future actions and to relate objects to other objects and substrates. The manual behaviour of capuchins is considered in different domains, such as motor planning, extractive foraging and tool use, in both captive and natural settings. Anatomofunctional and behavioural similarities to and differences from other haplorrhine species regarding manual dexterity are also discussed

Tactile information improves visual object discrimination in kea, Nestor notabilis, and capuchin monkeys, Sapajus spp.

In comparative visual cognition research, the influence of information acquired by nonvisual senses has received little attention. Systematic studies focusing on how the integration of information from sight and touch can affect animal perception are sparse. Here, we investigated whether tactile input improves visual discrimination ability of a bird, the kea, and capuchin monkeys, two species with acute vision, and known for their tendency to handle objects. To this end, we assessed whether, at the attainment of a criterion, accuracy and/or learning speed in the visual modality were enhanced by haptic (i.e. active tactile) exploration of an object. Subjects were trained to select the positive stimulus between two cylinders of the same shape and size, but with different surface structures. In the Sight condition, one pair of cylinders was inserted into transparent Plexiglas tubes. This prevented animals from haptically perceiving the objects' surfaces. In the Sight and Touch condition, one pair of cylinders was not inserted into transparent Plexiglas tubes. This allowed the subjects to perceive the objects' surfaces both visually and haptically. We found that both kea and capuchins (1) showed comparable levels of accuracy at the attainment of the learning criterion in both conditions, but (2) required fewer trials to achieve the criterion in the Sight and Touch condition. Moreover, this study showed that both kea and capuchins can integrate information acquired by the visual and tactile modalities. To our knowledge, this represents the first evidence of visuotactile integration in a bird species. Overall, our findings demonstrate that the acquisition of tactile information while manipulating objects facilitates visual discrimination of objects in two phylogenetically distant species

Does Presentation Format Influence Visual Size Discrimination in Tufted Capuchin Monkeys (Sapajus spp.)?

Most experimental paradigms to study visual cognition in humans and non-human species are based on discrimination tasks involving the choice between two or more visual stimuli. To this end, different types of stimuli and procedures for stimuli presentation are used, which highlights the necessity to compare data obtained with different methods. The present study assessed whether, and to what extent, capuchin monkeys\u27 ability to solve a size discrimination problem is influenced by the type of procedure used to present the problem. Capuchins\u27 ability to generalise knowledge across different tasks was also evaluated. We trained eight adult tufted capuchin monkeys to select the larger of two stimuli of the same shape and different sizes by using pairs of food items (Experiment 1), computer images (Experiment 1) and objects (Experiment 2). Our results indicated that monkeys achieved the learning criterion faster with food stimuli compared to both images and objects. They also required consistently fewer trials with objects than with images. Moreover, female capuchins had higher levels of acquisition accuracy with food stimuli than with images. Finally, capuchins did not immediately transfer the solution of the problem acquired in one task condition to the other conditions. Overall, these findings suggest that - even in relatively simple visual discrimination problems where a single perceptual dimension (i.e., size) has to be judged - learning speed strongly depends on the mode of presentation

Same/Different Concept Learning by Capuchin Monkeys in Matching-to-Sample Tasks

The ability to understand similarities and analogies is a fundamental aspect of human advanced cognition. Although subject of considerable research in comparative cognition, the extent to which nonhuman species are capable of analogical reasoning is still debated. This study examined the conditions under which tufted capuchin monkeys (Cebus apella) acquire a same/different concept in a matching-to-sample task on the basis of relational similarity among multi-item stimuli. We evaluated (i) the ability of five capuchin monkeys to learn the same/different concept on the basis of the number of items composing the stimuli and (ii) the ability to match novel stimuli after training with both several small stimulus sets and a large stimulus set. We found the first evidence of same/different relational matching-to-sample abilities in a New World monkey and demonstrated that the ability to match novel stimuli is within the capacity of this species. Therefore, analogical reasoning can emerge in monkeys under specific training conditions

Evoluzione del gene Hdh nei primati

Il gene Hdh si origina senza la tripletta CAG in Dictyostelium discoideum (Dd), circa 800 milioni di anni fa, prima della divergenza dei protostomi-deuterostomi (Zuccato et al., Physiol Rev 2010). La tripletta CAG compare in seguito ed ? esclusiva della branca dei deuterostomi (Tartari et al., Mol Biol Evol 2008). Due ripetizioni CAGs si trovano nel gene Hdh del riccio di mare (Strongylocentrotus purpuratus, Sp), la prima specie ad avere un sistema nervoso primitivo, e due ripetizioni si trovano anche nell\u27anfiosso (Branchiostoma floridae, Bf), che presenta un rudimentale tubo nervoso e un primo tentativo di cefalizzazione. Quattro ripetizioni CAG si riscontrano nei pesci pi? evoluti, negli anfibi e negli uccelli. Il numero di triplette CAG aumenta ulteriormente nei mammiferi e raggiunge la lunghezza massima nella nostra specie (Tartari et al., Mol Biol Evol 2008). In Homo sapiens il gene Hdh si trova sul braccio corto del cromosoma 4 e presenta la sequenza trinucleotidica ripetuta da 11 a 35 volte. Un recente studio su 278 individui normali ha rivelato che chi ha pi? CAG nel range sano ha pi? materia grigia (Muhlau et al., PlosOne 2012), indicazione del fatto che il numero di CAG potrebbe influire sulla normale struttura del cervello. Infatti, un numero di triplette CAG superiore a 35 causa la Corea di Huntington, una malattia neurodegenerativa che insorge tanto pi? precocemente quanto maggiore ? il numero delle ripetizioni CAG. Al fine di verificare se il progressivo incremento del numero di ripetizioni CAG nel gene Hdh durante l\u27evoluzione avesse un possibile ruolo nelle funzioni cognitive emergenti del cervello dei mammiferi, abbiamo analizzato il gene Hdh in diverse specie di primati non umani per analizzare la variabilit? interspecifica e intraspecifica. I risultati sperimentali e le ricostruzioni filogenetiche sostengono che il numero di ripetizioni CAG aumenta nel corso dell\u27evoluzione dei deuterostomi e sembra essere correlato con l\u27aspetto e/o l\u27evoluzione dei sistemi nervosi progressivamente pi? complessi

Artifact and Artifact Categorization: Comparing Humans and Capuchin Monkeys

International audienceWe aim to show that far-related primates like humans and the capuchin monkeys show interesting correspondences in terms of artifact characterization and categorization. We investigate this issue by using a philosophically-inspired definition of physical artifact which, developed for human artifacts, turns out to be applicable for cross-species comparison. In this approach an artifact is created when an entity is intentionally selected and some capacities attributed to it (often characterizing a purpose). Behavioral studies suggest that this notion of artifact is not specific to the human kind. On the basis of the results of a series of field observations and experiments on wild capuchin monkeys that routinely use stone hammers and anvils, we show that the notions of intentional selection and attributed capacity appear to be at play in capuchins as well. The study also suggests that functional criteria and contextualization play a fundamental role in terms of artifact recognition and categorization in nonhuman primates

METODOLOGIE A CONFRONTO IN UN COMPITO DI DISCRIMINAZIONE VISIVA. UNO STUDIO NEL CEBO DAI CORNETTI (SAPAJUS SPP.)

The aim of the study was to assess the ability of tufted capuchin monkeys (Sapajus spp.) to solve a visual discrimination problem presented with different procedures (computerised and non-computerised). The study was done in collaboration with the Max Planck Institute for Evolutionary Anthropology of Leipzig and it had yielded results of methodological relevance in comparative visual cognition research. In particular, it has shown that the presentation of the same discrimination task by using different methodologies, even if equivalent from a functional point of view, leads to significant differences in learning speed