The direct perception hypothesis: perceiving the intention of another’s action hinders its precise imitation

We argue that imitation is a learning response to unintelligible actions, especially to social conventions. Various strands of evidence are converging on this conclusion, but further progress has been hampered by an outdated theory of perceptual experience. Comparative psychology continues to be premised on the doctrine that humans and nonhuman primates only perceive others’ physical ‘surface behavior’, while mental states are perceptually inaccessible. However, a growing consensus in social cognition research accepts the Direct Perception Hypothesis: primarily we see what others aim to do; we do not infer it from their motions. Indeed, physical details are overlooked – unless the action is unintelligible. On this basis we hypothesize that apes’ propensity to copy the goal of an action, rather than its precise means, is largely dependent on its perceived intelligibility. Conversely, children copy means more often than adults and apes because, uniquely, much adult human behavior is completely unintelligible to unenculturated observers due to the pervasiveness of arbitrary social conventions, as exemplified by customs, rituals, and languages. We expect the propensity to imitate to be inversely correlated with the familiarity of cultural practices, as indexed by age and/or socio-cultural competence. The Direct Perception Hypothesis thereby helps to parsimoniously explain the most important findings of imitation research, including children’s over-imitation and other species-typical and age-related variations

Testing dogs in ape-like conditions: the effect of a barrier on dogs’ performance on the object-choice task

Recent reviews have found marked procedural and methodological differences in the testing of different taxonomic groups on the object-choice task. One such difference is the imposition of a barrier in the testing environment of nonhuman primates in the form of a cage, necessitated to ensure the experimenter’s safety. Here, we conducted two studies with domestic dogs (Canis lupus familiaris) in which we compared the performance of dogs tested from within a child’s playpen and dogs tested without this barrier present. In Study 1, in a within-subjects design, we found no effect of the barrier on dogs’ ability to use a pointing cue, but there was an increase in instances in which dogs failed to choose a cup. In Study 2, in a between-subjects design, dogs tested with a barrier failed to perform above chance, and were also more likely to fail to make a choice. When dogs tested without a barrier made an incorrect response, these were more likely to be incorrect choices than no choice errors. We discuss the implications of these differences in behavioural responses in function of the presence of a barrier and the necessity of ensuring matched conditions when comparing across species

Why vocal production of atypical sounds in apes and its cerebral correlates have a lot to say about the origin of language

Ackermann et al. mentioned the "acquisition of species-atypical sounds" in apes without any discussions. In our commentary, we demonstrate that these atypical sounds in chimpanzees not only include laryngeal sounds but also have a major significance regarding the origins of language, if we consider looking at their context of use, their social properties, their relations with gestures, their lateralization and their neurofunctional correlates as well

Systematics of the snub-nosed monkey: rhinopithecus

This paper will explore and summarize some of the published evidence for the systematic relationships of the colobine monkeys in the poorly known genus, Rhinopithecus. Rhinopithecus comprises four allopatric colobine species (or subspecies, see Groves, 1970, and below) that share a distinctive, turquoise-colored face and nose, the nose being characterized by a sharply upturned superior border with accessory flaps of skin, on the lateral nasal borders, that partially cover the nasal openings (Dollman, 1912; Milne-Edwards, 1870, 1872 [cited in Szalay & Delson, 1979]; Thomas, 1903). Their ecology and distribution will be briefly reviewed and an account of the history of their proposed taxonomic relations will be presented. Some locomotor characteristics of these monkeys will be (very briefly) evaluated to elucidate the relative primitiveness or specialization of these distinctive monkeys with respect to the eucatarrhine condition and other fossil and living forms

The method of validation by Zenith

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Gestural reference

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The effects of changes in the referential problem space of infants and toddlers (homo sapiens): implications for cross-species comparisons

Recent reviews have highlighted the tendency in the comparative literature to make claims about species’ relative evolutionarily adaptive histories based on studies comparing different species tested with procedurally and methodologically different protocols. One particularly contentious area is the use of the Object Choice Task (OCT), used to measure an individual’s ability to use referential cues, which is a core attribute of joint attention. We tested human children with versions of the OCT that have been previously used with dogs and nonhuman primates to see if manipulating the set-up would lead to behavioral changes. In Study 1, we compared the responses of 18-month-olds and 36-month-olds when tested with and without a barrier. The presence of a barrier between the child and the reward did not suppress performance but did elicit more communicative behavior. Moreover, the barrier had a greater facilitating effect on the younger children, who displayed more communicative behavior in comparison with older children, who more frequently reached through the barrier in acts of direct prehension. In Study 2, we compared the behavior of 36-month-olds when the reward was within reaching distance (proximal) and when it was out of reach (distal). The children used index-finger points significantly more in the distal condition and grabbed more in the proximal condition, showing that they were making spatial judgements about the accessibility of the reward rather than just grabbing per se. We discuss the implications of these within-species differences in behavioral responses for cross-species comparisons

Apes communicate about absent and displaced objects: methodology matters

Displaced reference is the ability to refer to an item that has been moved (displaced) in space and/or time, and has been called one of the true hallmarks of referential communication. Several studies suggest that nonhuman primates have this capability, but a recent experiment concluded that in a specific situation (absent entities) human infants display displaced reference but chimpanzees do not. Here we show that chimpanzees and bonobos of diverse rearing histories are capable of displaced reference to absent and displaced objects. It is likely that some of the conflicting findings from animal cognition studies are due to relatively minor methodological differences, but are compounded by interpretation errors. Comparative studies are of great importance in elucidating the evolution of human cognition, however, greater care must be taken with methodology and interpretation for these studies to accurately reflect species differences

Animal pointing: changing trends and findings from 30 years of research

The past 30 years have witnessed a continued and growing interest in the production and comprehension of manual pointing gestures in nonhuman animals. Captive primates with diverse rearing histories have shown evidence of both pointing production and comprehension, though there certainly are individual and species differences, as well as substantive critiques of how to interpret pointing or “pointing-like” gestures in animals. Early literature primarily addressed basic questions about whether captive apes point, understand pointing, and use the gesture in a way that communicates intent (declarative) rather than motivational states (imperative). Interest in these questions continues, but more recently there has been a dramatic increase in the number of papers examining pointing in a diverse array of species, with an especially large literature on canids. This proliferation of research on pointing and the diversification of species studied has brought new and exciting questions about the evolution of social cognition, and the effects of rearing history and domestication on pointing production and, more prolifically, comprehension. A review of this work is in order. In this paper we examine trends in the literature on pointing in nonhumans. Specifically, we examine publication frequencies of different study species from 1987 to 2016. We also review data on the form and function of pointing, and evidence either supporting or refuting the conclusion that various nonhuman species comprehend the meaning of pointing gestures

The performance of domestic dogs (Canis lupus familiaris) on two versions of the Object Choice Task

Object choice task (OCT) studies are widely used to assess the phylogenetic and ontogenetic distribution of the understanding of communicative cues, with this understanding serving as a proxy for the discernment of communicative intentions. Recent reviews have found systematic procedural and methodological differences in studies which compare performances across species on the OCT. One such difference concerns the spatial configuration of the test set-up, specifically the distances between the two containers (inter-object distance) and the subject–experimenter distance. Here, we tested dogs on two versions of the task: a central version in which the containers were in the subjects’ direct line of vision, and a peripheral version in which the position of the containers was distal to the subject. Half of the subjects were tested with a barrier in the testing environment (as nonhuman primates are tested) and the other half without. We found that dogs tested with a barrier performed significantly better in the central version and were more likely to fail to make a choice in the peripheral version. Dogs tested without a barrier showed comparable performance on the two versions. We thus failed to find support for the distraction hypothesis in dogs. We discuss potential explanations for this, highlighting how methodological differences in the presentation of the OCT can influence outcomes in studies using this paradigm