Brian Hare

Brian Hare
Duke University | DU · Department of Evolutionary Anthropology

Biological Anthropology, Ph.D.

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179
Publications
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Publications

Publications (179)
Chapter
Canine behavior has been studied for decades, but not until 1998 was it discovered that dogs have human-like cooperative communication skills that rival those of even our closest primate relatives. Ever since, canines have become subjects of increased research into the genetic underpinnings of these abilities. Here, we posit that domestication has...
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Forests are essential common-pool resources. Understanding school-aged children and adolescents’ motivations to conserve forests is critical for improving conservation education. In two experiments with school age children and adolescents (age range: 6-16; N=1088), we demonstrate that extrinsic, rather than intrinsic motivations lead to successful...
Article
Marine mammals are thought to have an energetically expensive lifestyle because endothermy is costly in marine environments. However, measurements of total energy expenditure (TEE; kcal/day) are available only for a limited number of marine mammals, because large body size and inaccessible habitats make TEE measurements expensive and difficult for...
Article
Although we know that dogs evolved from wolves, it remains unclear how domestication affected dog cognition. One hypothesis suggests dog domestication altered social maturation by a process of selecting for an attraction to humans.1, 2, 3 Under this account, dogs became more flexible in using inherited skills to cooperatively communicate with a new...
Article
To sustain life, humans and other terrestrial animals must maintain a tight balance of water gain and water loss each day.1-3 However, the evolution of human water balance physiology is poorly understood due to the absence of comparative measures from other hominoids. While humans drink daily to maintain water balance, rainforest-living great apes...
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** Full-text view-only SharedIt link: https://rdcu.be/b9o1a ** While our understanding of adult dog cognition has grown considerably over the past 20 years, relatively little is known about the ontogeny of dog cognition. To assess the development and longitudinal stability of cognitive traits in dogs, we administered a battery of tasks to 160 cand...
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Dogs’ special relationship with humans not only makes them ubiquitous in our lives, but working dogs specifically perform essential functions for us such as sniffing out bombs and pulling wheelchairs for the disabled. To enhance the performance of working dogs, it is essential to understand the cognitive skills that underlie and lead to their succe...
Preprint
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While we know that dogs evolved from wolves through a process of domestication, it remains unclear how this process may have affected dog cognitive development. Here we tested dog (N=44) and wolf (N=37) puppies, 5-18 weeks old, on a battery of temperament and cognition tasks. Dog puppies were more attracted to humans, read human gestures more skill...
Article
Poaching and habitat destruction in the Congo Basin threaten African great apes including the bonobo (Pan paniscus), chimpanzees (Pan troglodytes), and gorillas (Gorilla spp.) with extinction. One way to combat extinction is to reintroduce rescued and rehabilitated apes and repopulate native habitats. Reintroduction programs are only successful if...
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Trait heritability is necessary for evolution by both natural and artificial selection, yet we know little about the heritability of cognitive traits. Domestic dogs are a valuable study system for questions regarding the evolution of phenotypic diversity due to their extraordinary intraspecific variation. While previous studies have investigated mo...
Article
Synopsis Given their remarkable phenotypic diversity, dogs present a unique opportunity for investigating the genetic bases of cognitive and behavioral traits. Our previous work demonstrated that genetic relatedness among breeds accounts for a substantial portion of variation in dog cognition. Here, we investigated the genetic architecture of breed...
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Across mammals, increased body size is positively associated with lifespan. However, within species, this relationship is inverted. This is well illustrated in dogs (Canis familiaris), where larger dogs exhibit accelerated life trajectories: growing faster and dying younger than smaller dogs. Similarly, some age-associated traits (e.g., growth rate...
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Biodiversity is being lost at unprecedented rates. Limited conservation resources must be prioritized strategically to maximize impact. Here we introduce novel methods to assess a small-scale conservation education program in the Democratic Republic of Congo. Lola ya Bonobo is the world’s only sanctuary for one of humans’ two closest living relativ...
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Large-scale phylogenetic studies of animal cognition have revealed robust links between absolute brain volume and species differences in executive function. However, past comparative samples have been composed largely of primates, which are characterized by evolutionarily derived neural scaling rules. Therefore, it is currently unknown whether posi...
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Working dogs play a variety of important roles, ranging from assisting individuals with disabilities, to explosive and medical detection work. Despite widespread demand, only a subset of dogs bred and trained for these roles ultimately succeed, creating a need for objective measures that can predict working dog aptitude. Most previous research has...
Article
Dogs live in the dynamic human social networks full of strangers, yet they form strong and selective bonds with familiar caretakers. Little is known about how a bond is initially formed between a dog and a complete stranger. The first-impression hypothesis suggests that interacting with strangers can present an opportunity to form a mutualistic par...
Article
A key feature of human prosociality is direct transfers, the most active form of sharing in which donors voluntarily hand over resources in their possession. Direct transfers buffer hunter-gatherers against foraging shortfalls. The emergence and elaboration of this behaviour thus likely played a key role in human evolution by promoting cooperative...
Article
The cover image, by Kelsey Lucca et al., is based on the Short Report The development and flexibility of gaze alternations in bonobos and chimpanzees, DOI: 10.1111/desc.12598. Photo Credit: Jingzhi Tan.
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The goal of economics is to understand human preferences. Most research focuses on adult humans and does not take an evolutionary approach. In biology experimental evolution has been able to shift the preferences of animals. As an example, artificial selection for friendly behavior toward humans results in a syndrome of changes that strongly resemb...
Article
Humans closely monitor others' cooperative relationships [1, 2]. Children and adults willingly incur costs to reward helpers and punish non-helpers-even as bystanders [3-5]. Already by 3 months, infants favor individuals that they observe helping others [6-8]. This early-emerging prosocial preference may be a derived motivation that accounts for ma...
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Modern humans live in an “exploded” network with unusually large circles of trust that form due to prosociality toward unfamiliar people (i.e. xenophilia). In a set of experiments we demonstrate that semi-free ranging bonobos (Pan paniscus) – both juveniles and young adults – also show spontaneous responses consistent with xenophilia. Bonobos volun...
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By 2.5 years of age humans are more skilful than other apes on a set of social, but not nonsocial, cognitive tasks. Individual differences in human infants, but not chimpanzees, Pan troglodytes, are also explained by correlated variance in these cooperative communicative skills. Relative to nonhuman apes, domestic dogs, Canis familiaris, perform mo...
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The challenge of studying human cognitive evolution is identifying unique features of our intelligence while explaining the processes by which they arose. Comparisons with nonhuman apes point to our early-emerging cooperative-communicative abilities as crucial to the evolution of all forms of human cultural cognition, including language. The human...
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Among some haplorhine primates, including humans, relaxed yawns spread contagiously. Such contagious yawning has been linked to social bonds and empathy in some species. However, no studies have investigated contagious yawning in strepsirhines. We conducted an experimental study of contagious yawning in strepsirhines, testing ring-tailed and ruffed...
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Humans are distinguished from the other living apes in having larger brains and an unusual life history that combines high reproductive output with slow childhood growth and exceptional longevity. This suite of derived traits suggests major changes in energy expenditure and allocation in the human lineage, but direct measures of human and ape metab...
Article
We recently reported a study where chimpanzees and bonobos faced decisions between a ‘framed’ option that provided either one or two pieces of fruit, and an alternative option that always provided a constant number of peanuts. We found that apes (especially males) chose the framed option more when it was presented as a gain—apes initially saw one p...
Article
Monetary and biological rewards differ in many ways. Yet studies of human decision-making typically involve money, whereas nonhuman studies involve food. We therefore examined how context shifts human risk preferences to illuminate the evolution of decision-making. First, we assessed peoples' risk preferences across food, prizes, and money in a tas...
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Family dogs and dog owners offer a potentially powerful way to conduct citizen science to answer questions about animal behavior that are difficult to answer with more conventional approaches. Here we evaluate the quality of the first data on dog cognition collected by citizen scientists using the Dognition.com website. We conducted analyses to und...
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The emotional-reactivity hypothesis proposes that problem-solving abilities can be constrained by temperament, within and across species. One way to test this hypothesis is with the predictions of the Yerkes-Dodson law. The law posits that arousal level, a component of temperament, affects problem solving in an inverted U-shaped relationship: Optim...
Chapter
Behavioral heterochrony is the study of the timing and speed of development of behavior from an evolutionary perspective. Key to studies of behavioral heterochrony is the comparison of development across different species. Such studies can illuminate whether a trait thought to be unique to a given species might in fact have its precursors in the ea...
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We tested five lemur species-ring-tailed lemurs, ruffed lemurs, mongoose lemurs, black lemurs, and Coquerel's sifakas-(N = 52) in an experiment that evaluated skills for inhibitory control in a social context. First, two human experimenters presented identical food rewards; the "generous" experimenter allowed the subject to eat from her hand, where...
Article
This Special Issue of Behaviour includes twelve novel empirical papers focusing on the behaviour and cognition of both captive and wild bonobos (Pan paniscus). As our species less known closest relative, the bonobo has gone from being little studied to increasingly popular as a species of focus over the past decade. We suggest that bonobos are read...
Article
Bonobos are the only ape species, other than humans, that have demonstrated prosocial behaviors toward groupmates and strangers. However, bonobos have not been tested in the most frequently used test of prosociality in animals. The current study tested the other-regarding preferences of bonobos in two experiments using the prosocial choice task. In...
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Previous research has shown that chimpanzees exploit the behavior of humans and conspecifics more readily in a competitive than a cooperative context. However, it is unknown whether bonobos, who outperform chimpanzees in some cooperative tasks, also show greater cognitive flexibility in competitive contexts. Here we tested the cooperative-competiti...
Article
While natural observations show apes use grooming and play as social currency, no experimental manipulations have been carried out to measure the effects of these behaviours on relationship formation in apes. While previous experiments have demonstrated apes quickly learn the identity of individuals who will provide food in a variety of cooperative...
Article
Humans exhibit framing effects when making choices, appraising decisions involving losses differently from those involving gains. To directly test for the evolutionary origin of this bias, we examined decision-making in humans’ closest living relatives: bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). We presented the largest sample of non...
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Full-text available
The past 200,000 years of human cultural evolution have witnessed the persistent establishment of behaviors involving innovation, planning depth, and abstract and symbolic thought, or what has been called “behavioral modernity.” Demographic models based on increased human population density from the late Pleistocene onward have been increasingly in...
Data
Supplemental analyses for Experiment 2, subject information, and additional figures
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Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scal...
Article
There is very little research comparing great ape and human cognition developmentally. In the current studies we compared a cross-sectional sample of 2- to 4-year-old human children (n = 48) with a large sample of chimpanzees and bonobos in the same age range (n = 42, hereafter: apes) on a broad array of cognitive tasks. We then followed a group of...
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In a series of four experiments we investigated whether dogs use information about a human's visual perspective when responding to pointing gestures. While there is evidence that dogs may know what humans can and cannot see, and that they flexibly use human communicative gestures, it is unknown if they can integrate these two skills. In Experiment...
Article
Evolutionary theories suggest that ecology is a major factor shaping cognition in primates. However, there have been few systematic tests of spatial memory abilities involving multiple primate species. Here, we examine spatial memory skills in four strepsirrhine primates that vary in level of frugivory: ruffed lemurs (Varecia sp.), ring-tailed lemu...
Article
Humans and other primates are distinct among placental mammals in having exceptionally slow rates of growth, reproduction, and aging. Primates' slow life history schedules are generally thought to reflect an evolved strategy of allocating energy away from growth and reproduction and toward somatic investment, particularly to the development and mai...
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Full-text available
Studies suggest that haplorhine primates are sensitive to what others can see and hear. Using two experimental designs, we tested the hypothesis that ring-tailed lemurs (N = 16) are also sensitive to the visual and auditory perception of others. In the first task, we used a go/no-go design that required lemurs to exploit only auditory information....
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Full-text available
The social intelligence hypothesis suggests that living in large social networks was the primary selective pressure for the evolution of complex cognition in primates. This hypothesis is supported by comparative studies demonstrating a positive relationship between social group size and relative brain size across primates. However, the relationship...
Data
The procedure for Experiment 1. (MOV)
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The procedure for Experiment 2. (M4V)
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Supplemental analyses, Table S1, and Figure S1. (DOCX)
Article
The interface between cognition, emotion, and motivation is thought to be of central importance in understanding complex cognitive functions such as decision-making and executive control in humans. Although nonhuman apes have complex repertoires of emotional expression, little is known about the role of affective processes in ape decision-making. T...
Data
Setup for control trials in risk task. See SI Text for description. Food types pictured mirror those used with chimpanzees in the low-variance condition (banana is highly-preferred, cucumber is low-preferred, and peanuts are intermediately-preferred). (JPG)
Data
Bonobo temporal choice. The bonobo chooses the larger, delayed reward (3 pieces of food) over the smaller, immediate reward (1 piece of food). He scratches after his choice. (MOV)
Data
Chimpanzee risky choice. The chimpanzee chooses the risky option (that provides either a piece of banana – a highly-preferred food – or a piece of cucumber – a non-preferred food – with equal probability) over a safe option that provided 6 pieces of an intermediately preferred food (peanuts). After the experimenter reveals that he received a bad ou...
Data
Bonobo risky choice. The bonobo chooses the risky option (that provides either a piece of banana – a highly-preferred food – or a piece of lettuce – a non-preferred food – with equal probability) over a safe option that provided 6 pieces of an intermediately preferred food (papaya). After the experimenter reveals that he received a bad outcome, he...
Data
Chimpanzee temporal choice. The chimpanzee chooses the larger, delayed reward (3 pieces of food) over the smaller, immediate reward (1 piece of food). He scratches, vocalizes, and bangs after his choice. (MOV)
Article
Full-text available
Across three experiments, we explored whether a dog's capacity for inhibitory control is stable or variable across decision-making contexts. In the social task, dogs were first exposed to the reputations of a stingy experimenter that never shared food and a generous experimenter who always shared food. In subsequent test trials, dogs were required...
Article
Male reproductive effort is often strongly related to levels of the steroid hormone testosterone. However, little research has examined whether levels of testosterone throughout development might be tied to individual or species differences in the reproductive strategies pursued by adult males. Here, we tested the hypothesis that inter-specific dif...
Article
Reports an error in "Direct and Indirect Reputation Formation in Nonhuman Great Apes and Human Children" by Esther Herrmann, Stefanie Keupp, Brian Hare, Amrisha Vaish and Michael Tomasello (Journal of Comparative Psychology, Advanced Online Publication, Jul 2, 2012, np). The title should have read "Direct and Indirect Reputation Formation in Nonhum...
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Full-text available
Humans are believed to have evolved a unique motivation to participate in joint activities that first develops during infancy and supports the development of shared intentionality. We conducted five experiments with bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) (Total n = 119) to assess their motivation to spontaneously participate in jo...
Article
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Humans are thought to possess a unique proclivity to share with others - including strangers. This puzzling phenomenon has led many to suggest that sharing with strangers originates from human-unique language, social norms, warfare and/or cooperative breeding. However, bonobos, our closest living relative, are highly tolerant and, in the wild, are...
Data
Full-text available
Subject information of experiment 1 and 2. (PDF)
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Subject information of experiment 3 and 4. (PDF)
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Supplementary methods, results, discussion and references. (DOC)
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Photos of the setups of the four experiments: a) The one-way key system in experiment 1 and 2, viewed from the subject room. b) The general setup of experiment 3 and 4. This particular photo shows the subject, the baited tunnel, the divider, the one-way key in the locked position and the food as it was placed in experiment 4. (JPG)
Data
Setups of self-regard pre-test and no-food introduction of experiment 3–4: a) The self-regard pre-test of experiment 3 and 4. b) The no-food introduction of experiment 3 and 4, during which no other bonobos were present in adjacent rooms. In both phases, the subjects had to meet the corresponding criteria in five consecutive trials to proceed to th...
Data
Subjects voluntarily chose to and preferred to release the stranger in experiment 1. (AVI)
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Subjects voluntarily released the stranger but not the groupmate in experiment 2. (AVI)
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Subjects helped the recipient to acquire out-of-reach food in experiment 3. (AVI)
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Full-text available
Reproductive history of female bonobos from the sanctuary. (PDF)
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Subjects did not release the recipient in experiment 4. (AVI)
Article
Spatial cognition and memory are critical cognitive skills underlying foraging behaviors for all primates. While the emergence of these skills has been the focus of much research on human children, little is known about ontogenetic patterns shaping spatial cognition in other species. Comparative developmental studies of nonhuman apes can illuminate...
Article
Context can have a powerful influence on decision-making strategies in humans. In particular, people sometimes shift their economic preferences depending on the broader social context, such as the presence of potential competitors or mating partners. Despite the important role of competition in primate conspecfic interactions, as well as evidence t...