Grasping behavior in tufted capuchin monkeys (<i>Cebus apella</i>): Grip types and manual laterality for picking up a small food item

AbstractThis study investigates prehension in 20 tufted capuchins (Cebus apella) in a reaching task requiring individuals to grasp a small food item fixed to a tray. The aim was twofold: 1) to describe capuchins' grasping techniques in detail, focusing on digit movements and on different areas of contact between the grasping fingers; and 2) to assess the relationship between grip types and manual laterality in this species. Capuchins picked up small food items using a wide variety of grips. In particular, 16 precision grip variants and 4 power grip variants were identified. The most frequently used precision grip involved the distal lateral areas of the thumb and the index finger, while the most preferred kind of power grip involved the thumb and the palm, with the thumb being enclosed by the other fingers. Immature capuchins picked up small food items using power grips more often than precision grips, while adult individuals exhibited no significant preference for either grip type. The analysis performed on the time capuchins took to grasp the food and withdraw it from the tray hole revealed that 1) precision grips were as efficient as power grips; 2) for precision grips, the left hand was faster than the right hand; and 3) for power grips, both hands were equally quick. Hand preference analysis, based on the frequency for the use of either hand for grasping actions, revealed no significant hand bias at group level. Likewise, there was no significant relationship between grip type and hand preference. Am J Phys Anthropol, 2003. © 2003 Wiley‐Liss, Inc

Are you as fooled as I am? Visual illusions in human (Homo) and nonhuman (Sapajus, Gorilla, Pan, Pongo) primate species

It has been argued that humans’ susceptibility to visual illusions does not simply reflect cognitive flaws but rather specific functional adaptations of our perceptual system. The data on cross-cultural differences in the perception of geometric illusions seemingly support this explanation. Little is known, however, about the developmental trajectories of such adaptations in humans, let alone a conclusive picture of the illusionary susceptibility in other primate species. So far, most developmental or comparative studies have tested single illusions with varying procedural implementations. The current study aims at overcoming these limitations by testing human subjects of four different age classes (3- to 5 year-old children and adults) and five non-human primate species (capuchin monkeys, bonobos, chimpanzees, gorillas and orangutans) with an identical setup in five well-known geometric illusions (Horizontal-vertical, Ebbinghaus, Mueller-Lyer, Ponzo, Sander). Two food items of identical size were presented on separate trays with surrounding paintings eliciting the illusion of size differences and subjects were required to choose one of the items. Four of the five illusions elicited a strong effect in adult humans, and older children showed a greater susceptibility to illusions than younger ones. In contrast, only two illusions (Ebbingaus and Horizontal-vertical) elicited a mild effect on nonhuman primates with high variation within species and little variation between species. Our results suggests that humans learn to see illusions as they develop during childhood. They also suggest that future work should address how nonhuman primates’ experience of these illusion changes throughout their development.PostprintPeer reviewe

Making use of Capuchins’ behavioral propensities to obtain hair samples for DNA analyses

Genotyping wild and captive capuchins has become a priority and hair bulbs have high quality DNA. Here, we describe a method to non-invasively collect fresh-plucked strands of hair that exploits capuchins’ manual dexterity and propensity to grasp and extract food. The apparatus consists of a transparent tube baited with food. Its extraction requires the monkey to place its forearm in contact with double-sided tape applied on the inner surface of the tube entrance. The “tube” method, successfully implemented with captive (N=23) and wild (N=21) capuchins, allowed us to obtain hair bulbs from most individuals and usable genomic DNA was extracted even from a single bulb

Flexible power grip use by capuchin monkeys (Sapajus spp.)

Grasping behavior relies on both motor and cognitive skills. The variability of power grip actions in a reaching-for-grasping task has been assessed in capuchins monkeys (N=20). On average, each individual used more than five different grip types, revealing a flexible use of the hand and a preference for the use of the thumb in opposition to the other fingers. No evidence of hemispheric specialization was found, however action planning abilities varied as a function of age and task practice

Short-term memory effects on visual global/local processing in tufted capuchin monkeys (Sapajus spp.).

Nonhuman primates, differently from humans, are less proficient at processing global properties of visual compound stimuli. It has been suggested that humans preferentially process stimuli globally because this enables a more economical encoding of the stimuli. In this study we assessed the role of short-term memory (STM) in global/local processing by presenting tufted capuchin monkeys with Navon-type hierarchical figures in both simultaneous and delayed matching-to-sample tasks. Capuchins’ ability to discriminate hierarchical stimuli was evaluated as a function of increasing delay intervals (0.0, 0.5, 1.0, 2.0 and 3.0 sec) between the disappearance of the sample and the presentation of the comparison stimuli. The results showed that recognition accuracy for local features was above chance level with delays of up to 3.0 sec, as previously reported when capuchins were faced with nonhierarchical stimuli. By contrast, the recognition of global configurations was above chance level in simultaneous, 0.0 and 0.5 sec delay conditions but not at delay intervals of 1.0 sec or longer. These findings indicate that capuchins’ propensity to process the local properties of visual stimuli can be observed when a delay is interposed between the presentation of sample and comparison stimuli and was not reversed by increasing the delay. Moreover, our results show that capuchins’ local propensity was not reversed by increasing stimulus size. Overall, our study confirms crucial differences between human and nonhuman primates and adds new insights into the comparative research on visual grouping functions of these species

AN INERTIAL SENSORS-BASED METHOD FOR PHASES AND EVENTS IDENTIFICATION IN PARA-ROWING: TOWARDS AN ON-WATER PERFORMANCE ASSESSMENT

The aim of this study is to propose and validate an inertial sensors-based methodology for the para-rowing stroke cycles segmentation. One non-disabled athlete performed two para-rowing set-ups, simulating PR1 (arms and shoulders-AS) and PR2 (trunk and arms-TA) conditions. Catch and finish events of each stroke cycle were identified on the signals measured by three sensors located on the right forearm (FA), upper arm (UA), and on the trunk (T). Accuracy was quantified by identifying the same events on the 3D trajectory of one right hand-located marker. UA and FA sensors data lead to a more accurate detection of stroke events with respect to the T sensor (average error: 28.8ms, 29.0ms, 56.9ms). The present results open promising scenarios on the application of inertial sensors in para-rowing for real-time performance-related feedback to athletes and coaches

Análise do Controle de Estímulos resultante da Manipulação do número de escolhas em Treino Discriminativo com Macacos-Prego (Sapajus Sp.)

Previous studies evaluated the effect of presenting multiple copies of an S- on simple simultaneous discrimination S+/S- train­ing. The present study evaluated whether some control by the nominal features of the stimuli develops in this kind of procedure, in addition to control by the singularity of the S+ (Experiment I). The present study also qualitatively evaluated stimulus control relations produced in this kind of procedure (Experiment II). In Experiment I, capuchin monkeys (Sapajus sp.) underwent discriminative training with three different trial types (two, four, and nine choices). A stimulus control test evaluated whether performance could be maintained when the discriminations learned in the three different trial types where presented in a two-choice procedure. The results showed clear control by the nominal features of the stimuli. In Experiment II, a mask procedure was used to identify the established stimulus control relations (select and/or reject control). The results showed solid reject control for both subjects, with select control also present for one of the subjects. The present study contributes to the research area by presenting a more detailed analysis of stimulus control that is ap­plicable to several studies on the manipulation of the number of choices in discriminative training.Estudos anteriores avaliaram o efeito da apresentação de múltiplas cópias de S- em treino de discriminação simples simul¬tânea S+/S-. O presente estudo avaliou se, nesse tipo de procedimento, algum controle pelas características nominais dos estímulos se desenvolve, além do controle pela singularidade do S+ (Experimento I). Adicionalmente, o presente estudo avaliou qualitativamente as relações de controle produzidas neste tipo de procedimento (Experimento II). No Experimento I, macacos-prego (Sapajus sp.) foram submetidos a treino discriminativo com três tipos diferentes de tentativas (duas, quatro e nove escolhas). Um teste de controle de estímulos avaliou se o repertório aprendido podia ser mantido quando os estímulos utilizados nos três tipos de tentativa eram apre¬sentados na forma de duas escolhas. Os resultados apontam claramente controle pelas características nominais dos estímulos. No Ex¬perimento II, o procedimento de máscara foi utilizado para identificar as relações de controle (por seleção e/ou rejeição) desenvolvidas. Os resultados mostram sólido controle por rejeição para ambos os sujeitos, com controle por seleção também presente para um dos sujeitos. O presente trabalho contribui no sentido de aprofundar a análise do controle de estímulos em estudos sobre a manipulação do número de escolhas em treino discriminativo

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 (\u27\u27yoked-control\u27\u27 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\u27 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

Empirical experiments on intrinsic motivations and action acquisition: results, evaluation, and redefinition

This document presents Deliverable D3.2 of the EU-funded Integrated Project "IM-CLeVeR - Intrinsically Motivated Cumulative Learning Versatile Robots", contract n. FP7-ICT-IP-231722.The aims of the deliverable, as given in the original IM-CLEVER proposal were to identify new key empirical phenomena and processes, allowing the design of a second set of experiments. This report covers: (1) novelty detection and discovery of when/what/how of agency in experiments with humans ("joystick experiment") and Parkinson patients. (2) how object properties that stimulate intrinsically motivated interaction and facilitate the acquisition of adaptive knowledge and skills in monkeys and children ("board experiment")

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

Abstract 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 (&quot;yoked-control&quot; 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&apos; 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