共查询到20条相似文献,搜索用时 15 毫秒
1.
Brian K. Hall 《Journal of biosciences》2008,33(5):781-793
The neural crest has long fascinated developmental biologists, and, increasingly over the past decades, evolutionary and evolutionary
developmental biologists. The neural crest is the name given to the fold of ectoderm at the junction between neural and epidermal
ectoderm in neurula-stage vertebrate embryos. In this sense, the neural crest is a morphological term akin to head fold or
limb bud. This region of the dorsal neural tube consists of neural crest cells, a special population(s) of cell, that give
rise to an astonishing number of cell types and to an equally astonishing number of tissues and organs. Neural crest cell
contributions may be direct — providing cells — or indirect — providing a necessary, often inductive, environment in which
other cells develop. The enormous range of cell types produced provides an important source of evidence of the neural crest
as a germ layer, bringing the number of germ layers to four — ectoderm, endoderm, mesoderm, and neural crest. In this paper
I provide a brief overview of the major phases of investigation into the neural crest and the major players involved, discuss
how the origin of the neural crest relates to the origin of the nervous system in vertebrate embryos, discuss the impact on
the germ-layer theory of the discovery of the neural crest and of secondary neurulation, and present evidence of the neural
crest as the fourth germ layer. A companion paper (Hall, Evol. Biol. 2008) deals with the evolutionary origins of the neural crest and neural crest cells. 相似文献
2.
In humans, the susceptibility to yawn contagion has been theoretically and empirically related to our capacity for empathy. Because of its relevance to evolutionary biology, this phenomenon has been the focus of recent investigations in non-human species. In line with the empathic hypothesis, contagious yawning has been shown to correlate with the level of social attachment in several primate species. Domestic dogs (Canis familiaris) have also shown the ability to yawn contagiously. To date, however, the social modulation of dog contagious yawning has received contradictory support and alternative explanations (i.e., yawn as a mild distress response) could explain positive evidence. The present study aims to replicate contagious yawning in dogs and to discriminate between the two possible mediating mechanisms (i.e., empathic vs. distress related response). Twenty-five dogs observed familiar (dog’s owner) and unfamiliar human models (experimenter) acting out a yawn or control mouth movements. Concurrent physiological measures (heart rate) were additionally monitored for twenty-one of the subjects. The occurrence of yawn contagion was significantly higher during the yawning condition than during the control mouth movements. Furthermore, the dogs yawned more frequently when watching the familiar model than the unfamiliar one demonstrating that the contagiousness of yawning in dogs correlated with the level of emotional proximity. Moreover, subjects’ heart rate did not differ among conditions suggesting that the phenomenon of contagious yawning in dogs is unrelated to stressful events. Our findings are consistent with the view that contagious yawning is modulated by affective components of the behavior and may indicate that rudimentary forms of empathy could be present in domesticated dogs. 相似文献
3.
Kieran P. McNulty 《Evolution》2010,3(3):322-332
The evolutionary history of humans comprises an important but small branch on the larger tree of ape evolution. Today’s hominoids—gibbons,
orangutans, gorillas, chimpanzees, and humans—are a meager representation of the ape diversity that characterized the Old
World from 23–5 million years ago. In this paper, I briefly review this evolutionary history focusing on features important
for understanding modern ape and human origins. As the full complexity of ape evolution is beyond this review, I characterize
major geographic, temporal, and phylogenetic groups using a few flagship taxa. Improving our knowledge of hominoid evolution
both complicates and clarifies studies of human origins. On one hand, features thought to be unique to the human lineage find
parallels in some fossil ape species, reducing their usefulness for identifying fossil humans. On the other hand, the Miocene
record of fossil apes provides an important source for generating hypotheses about the ancestral human condition; this is
particularly true given the dearth of fossils representing our closest living relatives: chimpanzees and gorillas. 相似文献
4.
Extrapair paternity (EPP) has been observed in many formally monogamous species. Male pursuit of extrapair fertilizations
(EPF) is explained by the advantages of having offspring that receive essential paternal care from other males. Because females
are capable of exercising a degree of control over the post-copulatory sperm competition, EPP’s persistence indicates that
females benefit from EPF. Thus, EPP involves cooperation between mated females and extrapair males. On the other hand, mated
males exhibit a spectrum of anti-cuckolding strategies. Hence, extrapair attributes of diverse species and populations reported
in the literature are particular solutions of evolutionary games involving gender-specific cuckolding/anti-cuckolding strategies. Here we use game theoretical methods to study the effect
of male paternal effort conserving strategies in situations where females seek EPF for reasons of genetic compatibility and/or
in pursuit of genetic diversity for their offspring. Our results indicate that in these circumstances pursuit of EPF is the
only evolutionary stable female strategy. Males, on the other hand, have two, mutually exclusive, evolutionary stable strategies:
males that restrict parental care regardless of their mate’s fidelity, and males that never restrict parental care. That is,
when females seek EPF for reasons of fertility assurance and/or genetic diversity, the conditional male strategy—therein the
male’s parental efforts are based on his certainty of paternity—loses in competition with the unconditional strategies. 相似文献
5.
Evolutionary biology owes much to Charles Darwin, whose discussions of common descent and natural selection provide the foundations
of the discipline. But evolutionary biology has expanded well beyond its foundations to encompass many theories and concepts
unknown in the 19th century. The term “Darwinism” is, therefore, ambiguous and misleading. Compounding the problem of “Darwinism”
is the hijacking of the term by creationists to portray evolution as a dangerous ideology—an “ism”—that has no place in the
science classroom. When scientists and teachers use “Darwinism” as synonymous with evolutionary biology, it reinforces such
a misleading portrayal and hinders efforts to present the scientific standing of evolution accurately. Accordingly, the term
“Darwinism” should be abandoned as a synonym for evolutionary biology. 相似文献
6.
Use of symbols, the key to the biosemiotics field as to many others, required bigger brains which implied a promissory note for greater energy consumption; symbols are obviously expensive. A score years before the current estimate of 18–20% for the human brain’s metabolic demand on the organism, it was known that neural tissue is metabolically dear. This paper first discusses two evolutionary responses to this demand, on both of which there is some consensus. The first, assigning care of altricial infants with burgeoning brains (and in human infants the metabolic demand peaks at 65% of the total) to “allomothers” is not unique to humans. The second, using relatively small neurons as primates do, risks misfires past a certain minimal value. Moreover, in apparent paradox, there is an increasing consensus that large “Von Economo” neurons are critical for communication. This paper’s main contribution is the discussion of two further evolutionary tricks. The first is the use of self-similarity in the cortex, both in structure and process, to allow the cortex readily—and in energetic terms, parsimoniously—to shift between states in a high-dimensional space. This leads to discussion of the kind of formalism appropriate to model these shifts, a formalism which—it is tentatively suggested—may do double duty for the modeling of symbolic thought. The second trick is the superimposition on the background “white noise” of neural firing of EEG-detected waves like gamma. The paper describes a method, using the Hilbert transform, of calculating the dips in energy consumption as the brain is transitioned by gamma waves. It is hypothesized that consciousness may be a spandrel, the incidental result of a neurodynamic imperative that the brain enter a maximally sensitive (in sensory terms) “zero power” state a few times a second. If that is the case, then there are obvious benefits for health in meditation, which can be viewed as a state of consciousness extended over time by limiting afferent stimuli. 相似文献
7.
In responding to three reviews of Evolution in Four Dimensions (Jablonka and Lamb, 2005, MIT Press), we briefly consider the historical background to the present genecentred view of evolution,
especially the way in which Weismann’s theories have influenced it, and discuss the origins of the notion of epigenetic inheritance.
We reaffirm our belief that all types of hereditary information—genetic, epigenetic, behavioural and cultural—have contributed
to evolutionary change, and outline recent evidence, mainly from epigenetic studies, that suggests that non-DNA heritable
variations are not rare and can be quite stable. We describe ways in which such variations may have influenced evolution.
The approach we take leads to broader definitions of terms such as ‘units of heredity’, ‘units of evolution’, and ‘units of
selection’, and we maintain that ‘information’ can be a useful concept if it is defined in terms of its effects on the receiver.
Although we agree that evolutionary theory is not undergoing a Kuhnian revolution, the incorporation of new data and ideas
about hereditary variation, and about the role of development in generating it, is leading to a version of Darwinism that
is very different from the gene-centred one that dominated evolutionary thinking in the second half of the twentieth century. 相似文献
8.
Chimpanzee and hunter-gatherer intergroup aggression differ in important ways, including humans having the ability to form
peaceful relationships and alliances among groups. This paper nevertheless evaluates the hypothesis that intergroup aggression
evolved according to the same functional principles in the two species—selection favoring a tendency to kill members of neighboring
groups when killing could be carried out safely. According to this idea chimpanzees and humans are equally risk-averse when
fighting. When self-sacrificial war practices are found in humans, therefore, they result from cultural systems of reward,
punishment, and coercion rather than evolved adaptations to greater risk-taking. To test this “chimpanzee model,” we review
intergroup fighting in chimpanzees and nomadic hunter-gatherers living with other nomadic hunter-gatherers as neighbors. Whether
humans have evolved specific psychological adaptations for war is unknown, but current evidence suggests that the chimpanzee
model is an appropriate starting point for analyzing the biological and cultural evolution of warfare. 相似文献
9.
In view of its fundamental and pervasive influences and impacts on organism physiology and ecology, body size is recognized
as a key component of evolutionary fitness and serves as the cornerstone of a seminal contribution in freshwater zooplankton
ecology—the Size Efficiency Hypothesis (SEH) of Brooks & Dodson (Science 150:28–35, 1965). While the roles and implications of body size in predation and competition—central tenets of the SEH—have been widely considered
and reviewed, no broader integrated synthesis exists of the collective array of body size determinants and their implications
in the ecology in crustacean zooplankton—a numerically and functionally dominant group of aquatic organisms. Focusing on planktonic
Cladocera and Copepoda in inland waters, in particular, we provide a wide-ranging overview of the direct and/or indirect effects
of environmental conditions, consumable resources and biotic interactions that independently and/or collectively influence
the phenotypic expression of body size (particularly as length), both within and between species. Some indirect ultimate evolutionary
consequences of body size are considered, and we identify some controversies and unresolved issues related to this biologically
crucial trait. While by no means exhaustive, our overview reveals a complex nexus of extrinsic proximate abiotic and biotic
factors and interactions that influence body size, the phenotypic expression of which in natural systems commonly reflects
contrasting outcomes related to conflicting direct and/or indirect selective pressures. In general, however, body size (both
inter- and intra specifically) declines with rising temperature and increases with rising food supply (depending on its quality),
although both temperature and food supply exert contrary influences on particular taxa (or life history stages) under certain
environmental circumstances. Predation undoubtedly has an overriding influence on body size selection. Depending on its mechanistic
basis (visual, tactile or both in tandem), it selectively favours either small or large body size, both within (adults vs.
juveniles) and between prey species, which are accordingly often ‘size-trapped’ between contrasting selective pressures, with
consequent indirect effects. The bioenergetics of fundamental physiological processes undoubtedly set constraints on body
size and serve as the primary determinant. However, within such constraints, the phenotypic expression of body size reflects
its adaptive modification in response to the prevailing abiotic and biotic environment. As such, body size represents an emergent
ecological property, reflecting the outcome of specific circumstances and conditions, which vary both temporally within and
spatially between different ecosystems, and are accordingly context dependent. Nevertheless, underlying physiological advantages
of larger size (within and between species) among crustacean zooplankters—lower mass-specific metabolic rates (although recently
challenged), higher individual feeding rates (at least among cladocerans), potentially wider food size-ranges, better starvation
tolerances, higher potential fecundity, etc.—collectively favour the selection of increased body size, as predicted by the
SEH. Although competitive superiority of large size (measured in terms of minimal food requirements) has been confirmed experimentally,
this cannot be generalized to natural conditions, where conflicting and temporally variable pressures apply, and contribute
to generally mixed, and temporally variable body size compositions. Complex underlying ecological interactions and influences
ultimately determine the phenotypic expression of body size in directions consistent with fitness optimization under prevailing
circumstances. Certain specific and general deficiencies in information are identified. In particular, the overwhelming emphasis
on daphniid cladocerans as model study taxa in freshwater ecosystems has marginalized the acquisition of a comparably broad
and penetrating understanding of specific features both of non-daphniid cladoceran and copepod life histories and body size
selection. Among daphniid cladocerans, contemporary definitive understanding devolves largely from reductionist laboratory
approaches. Holistic re-integration of these mechanistic findings into natural system circumstances presents a difficult challenge
that is attracting increasingly attention. With regard to copepods, synthetic integration of the expansive marine knowledge
base appears crucial to inform and direct future investigations on freshwater taxa. The question of intrinsic body size regulation
in copepods and cladocerans, especially in regard to final phenotypic plasticity in body size expression, awaits resolution.
Overall, body size remains a multi-facetted and complex topic, offering promising challenges for further investigation. 相似文献
10.
Darwin’s contributions to evolutionary biology are well known, but his contributions to genetics are much less known. His
main contribution was the collection of a tremendous amount of genetic data, and an attempt to provide a theoretical framework
for its interpretation. Darwin clearly described almost all genetic phenomena of fundamental importance, such as prepotency
(Mendelian inheritance), bud variation (mutation), heterosis, reversion (atavism), graft hybridization (Michurinian inheritance),
sex-limited inheritance, the direct action of the male element on the female (xenia and telegony), the effect of use and disuse,
the inheritance of acquired characters (Lamarckian inheritance), and many other observations pertaining to variation, heredity
and development. To explain all these observations, Darwin formulated a developmental theory of heredity — Pangenesis — which
not only greatly influenced many subsequent theories, but also is supported by recent evidence. 相似文献
11.
Caretaker-infant attachment is a complex but well-recognized adaptation in humans. An early instance of (or precursor to)
attachment behavior is the dyadic interaction between adults and infants of 6 to 24 weeks, commonly called "babytalk." Detailed
analysis of 1 minute of spontaneous babytalk with an 8-week infant shows that the poetic texture of the mother’s speech—specifically
its use of metrics, phonetics, and foregrounding—helps to shape and direct the baby’s attention, as it also coordinates the
partners’ emotional communication. We hypothesize that the ability to respond to poetic features of language is present as
early as the first few weeks of life and that this ability attunes cognitive and affective capacities in ways that provide
a foundation for the skills at work in later aesthetic production and response. By linking developmental social processes
with formal cognitive aspects of art, we challenge predominant views in evolutionary psychology that literary art is a superfluous
byproduct of adaptive evolutionary mechanisms or primarily an ornament created by sexual selection.
David S. Miall is Professor of English at the University of Alberta in Canada. He is the author of essays on British Romantic
writers, empirical studies of readers’ responses to literature, hypertext and literary computing. Ellen Dissanayake is Visiting
Scholar at the Walter Chapin Simpson Center for the Humanities, University of Washington. Her most recent book is Art and Intimacy: How the Arts Began (2000). 相似文献
12.
Elainie Alenk?r Madsen Tomas Persson Susan Sayehli Sara Lenninger G?ran Sonesson 《PloS one》2013,8(10)
Contagious yawning has been reported for humans, dogs and several non-human primate species, and associated with empathy in humans and other primates. Still, the function, development and underlying mechanisms of contagious yawning remain unclear. Humans and dogs show a developmental increase in susceptibility to yawn contagion, with children showing an increase around the age of four, when also empathy-related behaviours and accurate identification of others’ emotions begin to clearly evince. Explicit tests of yawn contagion in non-human apes have only involved adult individuals and examined the existence of conspecific yawn contagion. Here we report the first study of heterospecific contagious yawning in primates, and the ontogeny of susceptibility thereto in chimpanzees, Pan troglodytes verus. We examined whether emotional closeness, defined as attachment history with the yawning model, affected the strength of contagion, and compared the contagiousness of yawning to nose-wiping. Thirty-three orphaned chimpanzees observed an unfamiliar and familiar human (their surrogate human mother) yawn, gape and nose-wipe. Yawning, but not nose-wiping, was contagious for juvenile chimpanzees, while infants were immune to contagion. Like humans and dogs, chimpanzees are subject to a developmental trend in susceptibility to contagious yawning, and respond to heterospecific yawn stimuli. Emotional closeness with the model did not affect contagion. The familiarity-biased social modulatory effect on yawn contagion previously found among some adult primates, seem to only emerge later in development, or be limited to interactions with conspecifics. The influence of the ‘chameleon effect’, targeted vs. generalised empathy, perspective-taking and visual attention on contagious yawning is discussed. 相似文献
13.
Individuals are often restricted to indirect cues when assessing the mate value of a potential partner. Females of some species
have been shown to copy each other’s choice; in other words, the probability of a female choosing a particular male increases
if he has already been chosen by other females. Recently it has been suggested that mate-choice copying could be an important
aspect of human mate choice as well. We tested one of the hypotheses, the so-called wedding ring effect—that women would prefer
men who are already engaged or married—in a series of live interactions between men and women. The results show that women
do not find men signaling engagement, or being perceived as having a partner, more attractive or higher in socioeconomic status.
Furthermore, signs of engagement did not influence the women’s reported willingness to engage in short-term or long-term relationships
with the men. Thus, this study casts doubt on some simplified theories of human mate-choice copying, and alternative, more
complex scenarios are outlined and discussed.
Tobias Uller works on broad issues in evolutionary biology, such as life-history evolution and evolutionary genetics. Christoffer
Johansson recently received his Ph.D. with a dissertation on biomechanics of swimming birds. Their collaborative work on humans
is focused on mate choice. 相似文献
14.
P. Thompson 《Human Evolution》1990,5(2):133-138
The relevance of evolutionary theory to ethics goes back to Darwin but until recently discussion employed evolutionary theory
to justify ethical, social and political positions. Recently, evolutionary theory has been used to explain the existence of
moral systems and moral propensities and, thereby, to provide a naturalistic basis for ethics. I argue that this approach
has advanced our understanding of the basis of moral systems and moral propensities but does not as yet adequately incorporate
the role of cognition in its account. Cognition has the effect of decoupling to some extent — though, of course, far from
fully — human moral systems from their evolutionary origins. In an adequate account, evolutionary theory will play a crucial
role but so also will our evolved cognitive abilities. 相似文献
15.
Anne E. Russon 《Primates; journal of primatology》1998,39(4):485-503
Orangutans share many intellectual qualities with African great apes and humans, likely because of their recent common ancestry.
They may also show unique intellectual adaptations because of their long evolutionary divergence from the African lineage.
This paper assesses orangutan intelligence in light of this evolutionary history. Evidence derives from observations of juvenile
ex-captive orangutans reintroduced to free forest life by the Wanariset Orangutan Reintroduction Project, East Kalimantan,
Indonesia. The intellectual qualities shared by great apes and humans point to a distinct “great ape” intelligence with hierarchization
as a pivotal cognitive mechanism. Evolutionary reconstructions jibe with this view and suggest that technically difficult
foods may have been key selection pressures. Orangutans should then show hierarchical intelligence when obtaining difficult
foods. Evidence on ex-captive orangutans' techniques for processing difficult foods concurs. Intellectual qualities distinct
to orangutans may owe to arboreal travel pressures; in particular arboreality may aggravate foraging problems. Evidence confirms
that ex-captive orangutans' techniques for accessing difficult foods located arboreally are intellectually complex—i.e. they
show hierarchization. These findings suggest other factors probably important to understanding great ape and orangutan forms
of intelligence and their evolutionary origins. 相似文献
16.
Patricia Adair Gowaty 《Human nature (Hawthorne, N.Y.)》1992,3(3):217-249
Evolutionary biology and feminism share a variety of philosophical and practical concerns. I have tried to describe how a
perspective from both evolutionary biology and feminism can accelerate the achievement of goals for both feminists and evolutionary
biologists. In an early section of this paper I discuss the importance of variation to the disciplines of evolutionary biology
and feminism. In the section entitled “Control of Female Reproduction” I demonstrate how insight provided by participation
in life as woman and also as a feminist suggests testable hypotheses about the evolution of social behavior—hypotheses that
are applicable to our investigations of the evolution of social behavior in nonhuman animals. In the section on “Deceit, Self-deception,
and Patriarchal Reversals” I have overtly conceded that evolutionary biology, a scientific discipline, also represents a human
cultural practice that, like other human cultural practices, may in parts and at times be characterized by deceit and self-deception.
In the section on “Femininity” I have indicated how questions cast and answered and hypotheses tested from an evolutionary
perspective can serve women and men struggling with sexist oppression.
Patricia Adair Gowaty studies the evolution of social behavior, particularly mating systems and sex allocation, primarily
in birds. She is most well-known for her long-term studies of eastern bluebirds, which began in 1977 and are on-going. She
was an undergraduate at H. Sophie Newcomb College of Tulane University (1963–1967). In the late sixties and early seventies,
while employed at the Bronx Zoo (New York Zoological Society), she belonged to a feminist “consciousness-raising” group. She
started graduate school in 1974 at the University of Georgia and received her Ph.D. from Clemson University (1980). She had
a postdoctoral position at the University of Oklahoma (1982–1983) and a visiting faculty position at Cornell University through
the Visiting Professorships for Women NSF program (1983–1984) before returning to her bluebird study sites at Clemson in 1985.
She has supported herself and her research efforts throughout her academic career on a series of awards and grants. She is
currently (1990–1995) supported by a Research Scientist Development Award from The National Institute of Mental Health. 相似文献
17.
Energy management that generates terrain following versus apex-preserving hopping in man and machine
While hopping, 12 subjects experienced a sudden step down of 5 or 10 cm. Results revealed that the hopping style was “terrain
following”. It means that the subjects pursued to keep the distance between maximum hopping height (apex) and ground profile
constant. The spring-loaded inverse pendulum (SLIP) model, however, which is currently considered as template for stable legged
locomotion would predict apex-preserving hopping, by which the absolute maximal hopping height is kept constant regardless
of changes of the ground level. To get more insight into the physics of hopping, we outlined two concepts of energy management:
“constant energy supply”, by which in each bounce—regardless of perturbations—the same amount of mechanical energy is injected,
and “lost energy supply”, by which the mechanical energy that is going to be dissipated in the current cycle is assessed and
replenished. When tested by simulations and on a robot testbed capable of hopping, constant energy supply generated stable
and robust terrain following hopping, whereas lost energy supply led to something like apex-preserving hopping, which, however,
lacks stability as well as robustness. Comparing simulated and machine hopping with human hopping suggests that constant energy
supply has a good chance to be used by humans to generate hopping. 相似文献
18.
B. Voorzanger 《Human Evolution》1990,5(2):107-118
Evolutionary biology is supposed to be relevant to ethics by a number of authors. Some of them believe that it may provide
and justify basic moral values. Others argue that evolutionary biology is relevant only in a negative way. They assume that
it reveals the illusory nature of any attempt to justify basic moral values. In this paper one example of either approach
is criticized.
An analysis of examples can hardly offer sufficient grounds for a general conclusion. Nevertheless I believe that evolutionary
theory is of little help when we deal with the most basic ethical questions. Three themes which are often though to provide
a link between evolutionary biology and (meta)ethics — altruism, sociality and human nature — do not in fact establish that
link. 相似文献
19.
Cladograms, phylogenetic trees that depict evolutionary relationships among a set of taxa, are one of the most powerful predictive
tools in modern biology. They are usually depicted in one of two formats—tree or ladder. Previous research (Novick and Catley
2007) has found that college students have much greater difficulty understanding a cladogram’s hierarchical structure when it
is depicted in the ladder format. Such understanding would seem to be a prerequisite for successful tree thinking. The present
research examined the effect of a theoretically guided manipulation—adding a synapomorphy on each branch that supports two
or more taxa—on students’ understanding of the hierarchical structure of ladder cladograms. Synapomorphies are characters
shared by a group of taxa due to inheritance from a common ancestor. Thus, their depiction on a cladogram may facilitate the
understanding of evolutionary relationships. Students’ comprehension was assessed in terms of success at translating relationships
depicted in the ladder format to the tree format. The results indicated that adding synapomorphies provided powerful conceptual
scaffolding that improved comprehension for students with both weaker and stronger backgrounds in biology. For stronger background
students, the benefit of adding synapomorphies to the ladders was comparable to that of approximately two hours of instruction
in phylogenetics that emphasized the ladder format. 相似文献
20.
Contagious yawning is a form of response facilitation found in humans and other primates in which observing a model yawning enhances the chance that the observer will also yawn. Because contagious yawning seems to be more easily triggered when models are conspecifics or have a strong social bond with the observer, it has been proposed that contagious yawning is linked to empathy. A possible way to test this hypothesis is to analyze whether individuals’ responses differ when they observe models yawning or performing different involuntary (i.e., nose wiping, scratching) and voluntary (i.e., hand closing, wrist shaking) actions that are not linked to empathy. In this study, we tested the four great ape species with two different setups by exposing them to a human experimenter repeatedly performing these actions online, and video-recorded conspecifics repeatedly performing these actions on a screen. We examined which behaviors were subject to response facilitation, whether response facilitation was triggered by both human models and video-recorded conspecifics, and whether all species showed evidence of response facilitation. Our results showed that chimpanzees yawned significantly more when and shortly after watching videos of conspecifics (but not humans) yawning than in control conditions, and they did not do so as a response to increased levels of anxiety. For all other behaviors, no species produced more target actions when being exposed to either model than under control conditions. Moreover, the individuals that were more “reactive” when watching yawning videos were not more reactive when exposed to other actions. Since, at least in chimpanzees, (1) subjects only showed response facilitation when they were exposed to yawning and (2) only if models were conspecifics, it appears that contagious yawning is triggered by unique mechanisms and might be linked to empathy. 相似文献