A comparative psychophysical approach to visual perception in primates

Studies on the visual processing of primates, which have well developed visual systems, provide essential information about the perceptual bases of their higher-order cognitive abilities. Although the mechanisms underlying visual processing are largely shared between human and nonhuman primates, differences have also been reported. In this article, we review psychophysical investigations comparing the basic visual processing that operates in human and nonhuman species, and discuss the future contributions potentially deriving from such comparative psychophysical approaches to primate minds.     

Neocortex size predicts deception rate in primates

Human brain organization is built upon a more ancient adaptation, the large brain of simian primates: on average, monkeys and apes have brains twice as large as expected for mammals of their size, principally as a result of neocortical enlargement. Testing the adaptive benefit of this evolutionary specialization depends on finding an association between brain size and function in primates. However, most cognitive capacities have been assessed in only a restricted range of species under laboratory conditions. Deception of conspecifics in social circumstances is an exception, because a corpus of field data is available that encompasses all major lines of the primate radiation. We show that the use of deception within the primates is well predicted by the neocortical volume, when observer effort is controlled for; by contrast, neither the size of the rest of the brain nor the group size exert significant effects. These findings are consistent with the hypothesis that neocortical expansion has been driven by social challenges among the primates. Complex social manipulations such as deception are thought to be based upon rapid learning and extensive social knowledge; thus, learning in social contexts may be constrained by neocortical size.     

The dentinoenamel junction in primates

Dental characteristics figure large in primate taxonomy because teeth fossilize commonly and reflect dietary adaptations. The mammalian dentinoenamel junction (DEJ) plays a crucial role throughout odontogenesis in determining the ultimate crown configuration, being the interface between the papilla and the dental cap. The final configuration of the dentin surface reflects the epithelium more closely than does the enamel surface of the crown. Enamel deposition occurs relatively late in calcification, often causing many changes from the pattern residing in the DEJ; the genetic determination of the two surfaces also differs. Comparative study of the DEJ (and its differences from the enamel crown) is a potential adjunct to dentition-based taxonomy and may help to resolve certain cusp homologies and morphogenetic order of appearance. Primate teeth were stripped of enamel after measurement, mapping, and anatomical observations on the original crown. The dentin surfaces thus revealed differ from the enamel surfaces in several respects and shed new light on such dental problem areas as the origin of the hypocone, the affinities of lorisoids and callitrichids, the monophyly of the anthropoid grade, and human affinities.     

The role of invasive trophoblast in implantation and placentation of primates

We here review the evolution of invasive placentation in primates towards the deep penetration of the endometrium and its arteries in hominoids. The strepsirrhine primates (lemurs and lorises) have non-invasive, epitheliochorial placentation, although this is thought to be derived from a more invasive type. In haplorhine primates, there is differentiation of trophoblast at the blastocyst stage into syncytial and cellular trophoblast. Implantation involves syncytiotrophoblast that first removes the uterine epithelium then consolidates at the basal lamina before continuing into the stroma. In later stages of pregnancy, especially in Old World monkeys and apes, cytotrophoblast plays a greater role in the invasive process. Columns of trophoblast cells advance to the base of the implantation site where they spread out to form a cytotrophoblastic shell. In addition, cytotrophoblasts advance into the lumen of the spiral arteries. They are responsible for remodelling these vessels to form wide, low-resistance conduits. In human and great apes, there is additional invasion of the endometrium and its vessels by trophoblasts originating from the base of the anchoring villi. Deep trophoblast invasion that extends remodelling of the spiral arteries to segments in the inner myometrium evolved in the common ancestor of gorilla, chimp and human.     

When maths trumps logic: probabilistic judgements in chimpanzees

When searching for hidden food, do chimpanzees take into account both the number of hidden items and the number of potential hiding locations? We presented chimpanzees with two trays, each of them containing a different food/cup ratio and therefore a different likelihood of finding a baited cup among empty alternatives. Subjects'' performance was directly influenced by the relative difference (probability ratio (PR)) between the two given probabilities. Interestingly, however, they did not appreciate the special value of a truly safe option (with P = 1.0). Instead, they seemed to ‘blindly’ rely on the PR between the two options, systematically preferring the more likely one once a certain threshold had been reached. A control condition ruled out the possibility of low-level learning explanations for the observed performance.     

Copulatory patterns of primates as viewed in broad mammalian perspective

The goals of this review are to classify the patterns of copulatory behavior displayed by various species of primates, to compare them to the patterns of nonprimate mammalian species, and to search for correlates of the various patterns. Copulatory patterns are classified in relation to the presence or absence of four defining attributes: a lock, thrusting during intromissions, multiple intromissions, and multiple ejaculations. Literature on copulation in 67 primate species is reviewed, and a tentative classification is proposed for 33 primate species. Although neither social organization nor genital morphology provides a fully satisfactory relationship, there are indications that variations in copulatory behavior are related to variations in genital morphology.     

A word in the hand: action, gesture and mental representation in humans and non-human primates

The movements we make with our hands both reflect our mental processes and help to shape them. Our actions and gestures can affect our mental representations of actions and objects. In this paper, we explore the relationship between action, gesture and thought in both humans and non-human primates and discuss its role in the evolution of language. Human gesture (specifically representational gesture) may provide a unique link between action and mental representation. It is kinaesthetically close to action and is, at the same time, symbolic. Non-human primates use gesture frequently to communicate, and do so flexibly. However, their gestures mainly resemble incomplete actions and lack the representational elements that characterize much of human gesture. Differences in the mirror neuron system provide a potential explanation for non-human primates' lack of representational gestures; the monkey mirror system does not respond to representational gestures, while the human system does. In humans, gesture grounds mental representation in action, but there is no evidence for this link in other primates. We argue that gesture played an important role in the transition to symbolic thought and language in human evolution, following a cognitive leap that allowed gesture to incorporate representational elements.     

Adoption in Anthropoid primates

Reports of adoption in nonhuman primates are reviewed, including spontaneous adoptions of orphans or infants whose mothers have been removed from the group, temporary adoptions of offspring of sick mothers, adoptions arising out of kidnapping, and adoptions resulting from manipulations involving presenting infants to adults. Adoptive behavioral patterns resemble nonadoptive alloparental patterns. The literature indicates certain trends: adult females, especially if lactating or in the late stages of pregnancy, are most likely to adopt neonates. Older infants are more likely to be adopted by juveniles or by adult males. Weaned or weanable orphans that get adopted have reasonable chances of survival, while orphans still reliant on milk are unlikely to survive. An infant adopted by an adult female will develop socially as a member of the female’s matriline. Adoptions involving closely related individuals are consistent with kin-selection theory. Others appear to reflect “reproductive error” arising out of an attraction to young infants. Yet other cases might reflect reciprocal altruism. Continued documentation of cases of adoption will yield more data on costs and benefits and on whether rates and forms of adoption, such as alloparental behavior, vary systematically with social systems.     

非人灵长类性打搅行为研究进展

性打搅行为是指非人灵长类社群内非交配个体对正在发生性行为个体的干扰行为,该行为在非人灵长类中普遍存在,通过综述目前已知的36种非灵长类的性打搅行为的报道,探讨性打搅行为的功能和意义。性打搅行为具有更高度的种间和种内差异,种间的性打搅的方式不同、同时受到社会结构和婚配制度的影响;在种内受到性别、年龄、等级等因素的影响。结合川金丝猴性打搅的研究结果,从性打搅的类型、被打搅的反应、性打搅的功能以及相关假说等方面入手,对非人灵长类性打搅行为进行系统总结,旨在为我国相关领域的研究提供参考,为生殖行为学研究者启发思路,推动本领域的发展。     

Cooperation creates selection for tactical deception

Conditional social behaviours such as partner choice and reciprocity are held to be key mechanisms facilitating the evolution of cooperation, particularly in humans. Although how these mechanisms select for cooperation has been explored extensively, their potential to select simultaneously for complex cheating strategies has been largely overlooked. Tactical deception, the misrepresentation of the state of the world to another individual, may allow cheaters to exploit conditional cooperation by tactically misrepresenting their past actions and/or current intentions. Here we first use a simple game-theoretic model to show that the evolution of cooperation can create selection pressures favouring the evolution of tactical deception. This effect is driven by deception weakening cheater detection in conditional cooperators, allowing tactical deceivers to elicit cooperation at lower costs, while simple cheats are recognized and discriminated against. We then provide support for our theoretical predictions using a comparative analysis of deception across primate species. Our results suggest that the evolution of conditional strategies may, in addition to promoting cooperation, select for astute cheating and associated psychological abilities. Ultimately, our ability to convincingly lie to each other may have evolved as a direct result of our cooperative nature.     

The evolution of face processing in primates

The ability to recognize faces is an important socio-cognitive skill that is associated with a number of cognitive specializations in humans. While numerous studies have examined the presence of these specializations in non-human primates, species where face recognition would confer distinct advantages in social situations, results have been mixed. The majority of studies in chimpanzees support homologous face-processing mechanisms with humans, but results from monkey studies appear largely dependent on the type of testing methods used. Studies that employ passive viewing paradigms, like the visual paired comparison task, report evidence of similarities between monkeys and humans, but tasks that use more stringent, operant response tasks, like the matching-to-sample task, often report species differences. Moreover, the data suggest that monkeys may be less sensitive than chimpanzees and humans to the precise spacing of facial features, in addition to the surface-based cues reflected in those features, information that is critical for the representation of individual identity. The aim of this paper is to provide a comprehensive review of the available data from face-processing tasks in non-human primates with the goal of understanding the evolution of this complex cognitive skill.     

Darting terrestrial primates in the wild: A primer

While a goal of many field primatologists is to observe subjects in as undisturbed a setting as possible, it is often necessary to anesthetize animals for any of a variety of reasons. In this paper, we review techniques for anesthetizing wild primates, based on our experience with more than a thousand such procedures carried out on baboons in East Africa. We consider the following: 1) rationales for anesthetizing a wild primate; 2) systems for the delivery of anesthetic and choice of anesthetic; 3) the darting process itself and issues relevant to the period between darting and the safe removal of the animal; 4) handling of an anesthetized primate; 5) medical complications associated with darting; 6) when to reanesthetize an animal; 7) the process of recovery from anesthesia and release of an awake animal; 8) safety issues for humans. The range of information that can be obtained through field anesthetizations, when carried out successfully, as well as the potential benefit for the animals involved, can be enormous. However, this process is not trivial from the standpoint of the dangers involved to both the subjects and to humans and because of the potential disruption of social behavior to the group. As such, anesthetizations in the field should not be carried out without a strong rationale and without a tremendous priority given to the safety and care of all involved. Am. J. Primatol. 44:155–167, 1998. © 1998 Wiley-Liss, Inc.     

Episodic memory in primates.

Episodic memory refers to a system of memory with the capacity to recollect specific events from an individual's life. Some psychologists have suggested that episodic memory is a uniquely human phenomenon. We challenge that idea and present evidence that great apes and other primates may possess episodic-like memory. We review criteria developed to assess episodic-like memory in nonhumans, and how they apply to primates. In particular, we discuss the criteria of Clayton et al. [2001], who stated that episodic-like memory is based on the retrieval of multiple and integrated components of an event. We then review eight studies examining memory in great apes and apply the Clayton et al. criteria to each of them. We summarize the evidence that is compatible with the existence of episodic-like memory, although none of the data completely satisfy the Clayton et al. criteria. Morover, feelings of pastness and feelings of confidence, which mark episodic memory in humans, have not been empirically addressed in nonhuman primates. Future studies should be directed at these aspects of memory in primates. We speculate on the functional significance of episodic memory in nonhuman primates.     

Sexual conflict in primates

Sexual conflict is increasingly recognized as a major force for evolutionary change and holds great potential for delineating variation in primate behavior and morphology. The goals of this review are to highlight the rapidly rising field of sexual conflict and the ongoing shift in our understanding of interactions between the sexes. We discuss the evidence for sexual conflict within the Order Primates, and assess how studies of primates have illuminated and can continue to increase our understanding of sexual conflict and sexual selection. Finally, we introduce a framework for understanding the behavioral, anatomical, and genetic expression of sexual conflict across primate mating systems and suggest directions for future research.     

DNA fingerprinting in three species of neotropical primates

DNA fingerprinting allows the simultaneous detection of a large number of hypervariable loci consisting of highly polymorphic tandem repeat units that are extensively dispersed in the genome. With the 33.6 human minisatellite probe, hypervariable fragments were detected, for the first time, in the genome of three different species of wild-caught neotropical primates: Aotus infulatus, Aotus azarae, and Cebus apella. As in the human, these species were highly polymorphic, showing distinctive, individual-specific patterns. Estimates of relatedness within each group were calculated from interspecific comparisons based on the number of shared fragments between individuals. This work shows that the 33.6 human minisatellite probe can be very useful for increasing our understanding of population dynamics and behavior of these species in their natural habitat. © 1996 Wiley-Liss, Inc.     

Use of florfenicol in non-human primates

Studies were undertaken to determine if florfenicol, an antimicrobial agent structurally similar to chloramphenicol, could be used as an effective broad spectrum antibiotic for the treatment of bacterial infections in primates. Florfenicol was developed as an injectable antibiotic for use in cattle on an every other day dosing schedule. Its broad spectrum activity, long duration of action following i.m. administration, and its safety as compared with chloramphenicol made it an attractive antibiotic for use in non-human primates. Previous studies had shown that florfenicol is effective against common primate pathogens such as Salmonella, Klebsiella, Escherichia coli, Bordetella bronchiseptica, Streptococcus pneumoniae, Staphylococcus spp., and Yersinia pseudotuberculosis. We performed experiments on a total of 15 macaques. The animals were given florfenicol at 50 mg/kg i.m. and blood samples taken at various time points. Serum was evaluated for florfenicol absorption. Necropsies were also performed to determine if major organs were affected and to determine the effects of i.m. injection of florfenicol. We determined that florfenicol given every 48 hours in rhesus macaques results in blood levels that were acceptable for therapeutic use. The effect on muscle tissue of i.m. injection was similar to ketamine and normal saline. There were no gross lesions observed and no changes with tissues submitted for histology. Our work shows that with further studies, florfenicol may be useful when injectable antibiotic therapy is required in non-human primates.