Effects of captions on viewers' perceptions of images depicting human-primate interaction

Promoting human contact with wildlife can be harmful to animal conservation and welfare by exposing animals to unsafe situations and driving demand for wildlife tourism and exotic pets. Conservationists and researchers justifiably use social media to raise awareness, but professionals posting pictures of themselves with animals can have unintended negative consequences for conservation. Though the International Union for Conservation of Nature Best Practice Guidelines for Responsible Images of Non-Human Primates suggests researchers and animal professionals provide context in captions of images of humans interacting with primates, there is little research investigating whether this approach is effective. We investigated whether informative captions affect viewers' desires to have primates as pets and attitudes toward wildlife conservation. Using 4 mock Instagram posts depicting human-gorilla and human-slender loris interactions, we surveyed 2977 respondents to assess the effect of captions on viewers' perceptions of the images and primate conservation. Likert scale response data were analyzed with ordered probit regression models. Captions clearly contextualizing an image as research resulted in a significantly higher agreement that posts depicted wildlife research (gorilla β = 0.28 [SE 0.06], p < 0.001; loris β = 0.18 [0.06], p = 0.002), but such captions resulted in no significant difference in responses regarding viewers' desires to own primates as pets or questions regarding the primates' conservation statuses. Although most participants agreed the primates were endangered, more than 56% and 59%, respectively, stated they would have a gorilla or loris as a pet, that they would make good pets, or both, further supporting the conclusion that captions do not minimize harmful impacts of images of human-primate interactions.

Choice, control, and animal welfare: definitions and essential inquiries to advance animal welfare science

The ways in which humans can support good welfare for animals in their care is an ongoing subject of debate: some place emphasis on the animals' physical health; others, on animals' ability to live "natural lives"; and others on animals' affective states or psychological wellbeing. Recently, there has been an increase in interest in how an animal's ability to exercise control over its environment could impact their welfare. In this article, we take the stance that the relevant aspects of the first two concepts of animal welfare (physical health, natural lives) are largely addressed when an animal's psychological wellbeing is prioritized. Through that lens, we review the current state of the literature regarding the psychology of control, and the intersection between choice, control, and welfare. We clarify terms to support future work, and propose future directions that could lead to a better understanding of the psychological benefits of choice and control and ultimately inform animal care decisions.

Chimpanzees organize their social relationships like humans

Human relationships are structured in a set of layers, ordered from higher (intimate relationships) to lower (acquaintances) emotional and cognitive intensity. This structure arises from the limits of our cognitive capacity and the different amounts of resources required by different relationships. However, it is unknown whether nonhuman primate species organize their affiliative relationships following the same pattern. We here show that the time chimpanzees devote to grooming other individuals is well described by the same model used for human relationships, supporting the existence of similar social signatures for both humans and chimpanzees. Furthermore, the relationship structure depends on group size as predicted by the model, the proportion of high-intensity connections being larger for smaller groups.

Do zoo-housed primates retreat from crowds? A simple study of five primate species

An animal's welfare state is directly influenced by the mental state, which is shaped by experiences within the environment throughout the animal's life. For zoo-housed animals, visitors to the zoo are a large part of that environment and a fluctuating influence within it. This study examines the impact of zoo visitors on the space use of five species of zoo-housed primates (Eastern black-and-white colobus monkeys, Colobus guereza, n = 5, Allen's swamp monkeys, Allenopithecus nigroviridis, n = 2, DeBrazza's monkeys, Cercopithecus neglectus, n = 3, Bolivian gray titi monkeys, Callicebus donacophilus, n = 3, and crowned lemurs, Eulemur coronatus, n = 3). Specifically, we considered whether primates' distance from visitor areas changed as crowd sizes increased. Data were collected using the ZooMonitor app. Observers recorded spatial coordinates for each animal over periods ranging from 12 to 32 months. Data were analyzed using two types of regression models (linear and logistic) to examine the influence of visitors on the location of the primates. Both analyses revealed a statistically significant but small decrease in primate distance from visitor viewing glass as the number of visitors increased. Behavioral indicators of welfare were also unaffected by the presence of visitors. These results suggest that, with additional validation, distance from visitors may be one promising, simple way to evaluate the influence of visitors on primate welfare.

Younger generations are more interested than older generations in having non-domesticated animals as pets

The trade and private ownership of non-domesticated animals has detrimental effects on individual animals and their wild populations. Therefore, there is a need to understand the conditions that motivate and dissuade interest in non-domesticated pet ownership. Past research has demonstrated that the way in which non-domesticated animals are portrayed in images influences the public’s perception that they are suitable as pets. We conducted an online survey of people residing in the United States to investigate how viewing images that could be realistically captured in the zoo and broader tourism industries impact the degree to which people report interest in having that animal as a pet. We focused on two species, reticulated pythons (Malayopython reticulatus) and two-toed sloths (Choloepus hoffmanni), and presented each species in six different visual contexts. After viewing an image, respondents reported interest in pet ownership on a four-point Likert scale. Each species was studied separately in a between-subjects design and results were analyzed using ordinal logistic regression models. Thirty-nine percent of respondents reported interest in sloth pet ownership, and 21% reported interest in python pet ownership. However, contrary to our hypotheses, we found that viewing these species in different visual contexts did not significantly affect survey respondents’ reported interest in having either species as a pet. Generation was a significant predictor of interest in both sloth and python pet ownership, with younger generations reporting more interest in having these species as pets. Male respondents reported more interest in python pet ownership, whereas there were no significant differences between genders regarding interest in sloth ownership. We consider how modern media exposure to animals in unnatural contexts may relate to the generational effect and discuss priorities for future research to better understand the development of individual interests in non-domesticated pet ownership.

The Welfare of Domestic Goats (Capra hircus) in a Zoo-Based Animal-Visitor Interaction Program

We investigated whether the welfare of domestic goats in an animal-visitor interaction experience at a zoo was affected by the presence and behavior of visitors. We considered how the number of visitors in the goats’ habitat and visitor proximity to the goats impacted goat behavior. We also considered the goats’ behavior toward visitors, use of retreat space, and whether the visitors’ interaction style, specifically, how the visitors groomed the goats, was predictive of changes in the goats’ behavior. We conducted 29 hr of focal follows on 7 domestic goats (Capra hircus) at Lincoln Park Zoo, and analyzed data using mixed effects models. We found that goats preferred to be in the visitor yard as visitor numbers increased, and goat behaviors did not change as visitor numbers increased to the maximum allowed (16 people). There were no differences in rates of conspecific aggression or affiliation based on visitor presence or visitor interactions. However, there was a decrease in feeding and increase in self-maintenance behaviors specifically while visitors were in close proximity and interacting with goats. Furthermore, visitor-directed behavior, specifically head tossing, was more common when visitors groomed goats in an improper way. Overall, this study demonstrates that domestic goat welfare was relatively unaffected by the simple presence of visitors when maximum visitor limits were in place and retreat options were available, but that goats were sensitive to visitor interaction styles. These findings support the idea that domestic goats may be appropriate candidates for human-visitor interaction programs under specific conditions.

The relationship between personality, season, and wounding receipt in zoo-housed Japanese macaques (Macaca fuscata): A multi-institutional study

It is important to those managing Japanese macaques (Macaca fuscata) in captive settings to understand predictors of wounding. While studies have demonstrated that season (breeding or nonbreeding) and sex predict rates of wounding received by zoo-housed Japanese macaques, we investigated whether individual differences in personality ratings also might explain some of the observed interindividual variance in wounding. Such patterns were previously observed in rhesus macaques (M. mulatta), such that individuals rated higher on Anxiety and Confidence received greater wounding. Here, we collected wounding data over 24 months on 48 Japanese macaques from eight AZA-accredited zoos. Each macaque was also rated by keepers using a 26-item personality questionnaire. Principle components analysis of these ratings revealed four personality components: Openness, Friendliness, Dominance, and Anxiety/Reactivity. The model with the best fit revealed an interaction effect between season (breeding vs. nonbreeding) and the personality component Friendliness, such that individuals rated higher on Friendliness incurred fewer wounds in the nonbreeding season. The second-best model revealed both a main effect of the season as well as an interaction effect between season and Openness, such that macaques rated higher in Openness received more wounds in the nonbreeding season than those rated lower in Openness. Thus, as with rhesus macaques, personality mediated wounding receipt rate in Japanese macaques, although different personality components explained interindividual variance in wounding for these two species. These differences likely reflect species differences in behavior and personality structure, as well as the influence of differing management practices, highlighting the importance of species-specific approaches for captive primate care and welfare. This study provides further support for understanding primate personality to create individualized strategies for their care.

Cofeeding tolerance in chimpanzees depends on group composition: a longitudinal study across four communities

Social tolerance is generally treated as a stable, species-specific characteristic. Recent research, however, has questioned this position and emphasized the importance of intraspecific variation. We investigate the temporal stability of social tolerance in four groups of sanctuary-housed chimpanzees over eight years using a commonly employed measure: experimental cofeeding tolerance. We then draw on longitudinal data on the demographic composition of each group to identify the factors associated with cofeeding tolerance. We find appreciable levels of variation in cofeeding tolerance across both groups and years that correspond closely to changes in group-level demographic composition. For example, cofeeding tolerance is lower when there are many females with young infants. These results suggest that social tolerance may be a "responding trait" of chimpanzee sociality, reflecting individual-level behavioral responses to social changes. Additional, experimental research is needed to better model the causal drivers of social tolerance within and among species.

Domestic Animal Welfare at the Zoo: The Impact of an Animal Visitor Interaction Program on Chickens

Many modern zoos strive to create connections between guests and animals through animal visitor interaction (AVI) programs. However, there has been relatively little research into the effect of AVI programs on the welfare of program animals. Previous research has revealed three factors that may affect AVI program animal welfare: species differences, handling and transport, and the provision of choice and control. We assessed the effects of an AVI program designed with these factors in mind on the behavior of a flock (N = 16) of zoo-housed domestic chickens (Gallus gallus). Behavioral data were collected on program days and on non-program (control) days, and we considered the time leading up to the program, the program itself, and the time immediately following the program. When comparing flock behavior on program days to control days, we found no differences in behavioral indicators of welfare during the time leading up to the program and during the program. Rates of aggression, however, were significantly greater after the program had concluded compared to the same time period on matched control days, but still occurred infrequently. Additionally, we recorded the spatial location of each animal while the program occurred and found that the chickens did not spend significantly more or less time in the feeding zone as visitor participation increased, although there were individual differences within the flock. We conclude that the relatively small behavioral changes seen were not indicative of a change in welfare and consider those results in the context of the program design.

Food Cleaning by Japanese Macaques: Innate, Innovative or Cultural?

Japanese macaques (Macaca fuscata) display a number of cultural behaviours including food washing, stone handling and certain grooming techniques. These are deemed cultural behaviours because it is presumed that they are socially learned and, importantly, that social learning is essential for their emergence. Recently, however, research has revealed that culturally naïve primates can re-innovate presumed cultural behaviours. These behaviours are said to fall within that species' "zone of latent solutions" (ZLS). A notable cultural behaviour of Japanese macaques is food washing, first reported by Japanese researchers studying wild Japanese macaques in the 1950s. To test whether culturally naïve Japanese macaques would spontaneously wash food and also, therefore, whether food-washing behaviour is within their ZLS, we presented 12 zoo-housed macaques with sweet potato covered in sand near a pool in their exhibit. Over 11 days we recorded the macaques' behaviour. While 11 of the 12 macaques ate the potato pieces, none washed them. However, 4 macaques cleaned their food, brushing off the sand using their hand or rubbing the potato against their body or another food item, using three distinct techniques. We found no change over time in the rate at which monkeys cleaned or consumed potato, but there was a significant positive correlation between the number of potato pieces a monkey ate and the number of cleaning behaviours performed. We conclude that, minimally, food-cleaning behaviour is within macaques' ZLS.

Sex and season predict wounds in zoo-housed Japanese macaques (Macaca fuscata): A multi-institutional study

Japanese macaque societies are characterized by frequent intragroup conflict both in free-ranging and zoo-housed conditions. In zoos, understanding the factors that contribute to wounding is of interest because this knowledge can aid in proactive husbandry and management planning that can minimize the negative impacts wounding can have on individual welfare. This study sought to determine whether the variables sex, season and age predicted wounding rates. Data were collected for 24 months on 119 Japanese macaques living in 10 zoos, and we analyzed the contribution of variables using generalized linear mixed models. A total of 1,007 wounds were reported, and the best model included the interaction between sex and season. Follow-up analyses revealed that females incurred more wounds than males, and this sex difference was more pronounced during the breeding compared to the nonbreeding season. On average, individuals received 4.67 (±SEM: 0.55) wounds per year and 77.31% of the population incurred at least one wound in the study period. The majority of wounds were superficial and did not require veterinary intervention. Wound locations were not randomly distributed across body regions and were most often reported on the face. Finally, macaques living in larger social groups experienced more wounds, on average. This study represents the first quantification of wounding in this species and may provide insight to help inform husbandry and management strategies in zoos.

Chimpanzee culture extends beyond matrilineal family units

The 'grooming handclasp' is one of the most well-established cultural traditions in chimpanzees. A recent study by Wrangham et al.[1] reduced the cultural scope of grooming-handclasp behavior by showing that grooming-handclasp style convergence is "explained by matrilineal relationship rather than conformity" [1]. Given that we previously reported cultural differences in grooming-handclasp style preferences in captive chimpanzees [2], we tested the alternative view posed by Wrangham et al.[1] in the chimpanzee populations that our original results were based on. Using the same outcome variable as Wrangham et al.[1] - the proportion of high-arm grooming featuring palm-to-palm clasping - we found that matrilineal relationships explained neither within-group homogeneity nor between-group heterogeneity, thereby corroborating our original conclusion that grooming-handclasp behavior can represent a group-level cultural tradition in chimpanzees.

A Comparison of Sequential Learning Errors Made by Apes and Monkeys Reveals Individual but not Species Differences in Learning

Using methods comparable to those used previously to test closely-related taxa (Pan troglodytes and Macaca mulatta), our aim was to better understand how gorillas (Gorilla gorilla gorilla) and Japanese macaques (M. fuscata) learn sequences. Using a disappearing-type simultaneous chain, we trained five gorillas and eight macaques on a two-item list of colored stimuli presented via touchscreens. There was no difference across species in the number of trials required to learn the two-item list. We added a third item to the list as each subject reached criterion. We then analyzed the subjects’ first 30 trials with the three-item list and found that the rate of successfully sequencing the list varied by subject but not by species. In their first 30 trials of the three-item list, subjects selected the second item correctly only at chance, suggesting they had only encoded the first symbol when learning the two-item list. One gorilla, tested on longer sequences, showed similar responses: when first presented with a newly-lengthened list, he only selected the penultimate item at chance levels. Thus, the primates’ errors with newly-lengthened lists is suggestive of the chaining theory of learning. These results highlight similarities in list learning of these two distantly-related primate species as well as the clear intra-species variation in learning.

A multi-institutional assessment of a short-form personality questionnaire for use with macaques

There are two commonly-used methods for calculating primates' personality dimensions, behavioral assessments and surveys, which can be used separately or in conjunction. However, these methods have limitations. Behavioral assessments, such as the novel object test or human intruder test, often require subjects to be separated and demand highly-controlled conditions. This is likely not feasible in many zoological institutions. Furthermore, it may be difficult to replicate methods across institutions. While surveys are easier to implement, the most commonly used one - the Hominoid Personality Questionnaire (HPQ) - is long and can be time consuming to complete, especially if multiple individuals need assessing. Therefore, we developed a short-form personality questionnaire for use with macaques. We aimed to retain elements of published scales while creating a tool that would be less time consuming to complete. After creating a novel 26-item scale (28 fewer items than the HPQ), we gathered ratings for 63 Japanese macaques (Macaca fuscata) living in eight zoos accredited by the Association of Zoos and Aquariums. Using principal components analysis, we identified four components to describe the Japanese macaque personality: Openneness, Friendliness, Dominance, and Anxiety/Reactivity. While further testing is required to fully validate this scale, we tested for the convergent validity of our questionnaire by correlating the responses of a subset of the monkeys to a novel object and assessed the face validity of our scale in comparison to previously-published scales.

Studying primate cognition in a social setting to improve validity and welfare: a literature review highlighting successful approaches

BACKGROUND

Studying animal cognition in a social setting is associated with practical and statistical challenges. However, conducting cognitive research without disturbing species-typical social groups can increase ecological validity, minimize distress, and improve animal welfare. Here, we review the existing literature on cognitive research run with primates in a social setting in order to determine how widespread such testing is and highlight approaches that may guide future research planning.

SURVEY METHODOLOGY

Using Google Scholar to search the terms "primate" "cognition" "experiment" and "social group," we conducted a systematic literature search covering 16 years (2000-2015 inclusive). We then conducted two supplemental searches within each journal that contained a publication meeting our criteria in the original search, using the terms "primate" and "playback" in one search and the terms "primate" "cognition" and "social group" in the second. The results were used to assess how frequently nonhuman primate cognition has been studied in a social setting (>3 individuals), to gain perspective on the species and topics that have been studied, and to extract successful approaches for social testing.

RESULTS

Our search revealed 248 unique publications in 43 journals encompassing 71 species. The absolute number of publications has increased over years, suggesting viable strategies for studying cognition in social settings. While a wide range of species were studied they were not equally represented, with 19% of the publications reporting data for chimpanzees. Field sites were the most common environment for experiments run in social groups of primates, accounting for more than half of the results. Approaches to mitigating the practical and statistical challenges were identified.

DISCUSSION

This analysis has revealed that the study of primate cognition in a social setting is increasing and taking place across a range of environments. This literature review calls attention to examples that may provide valuable models for researchers wishing to overcome potential practical and statistical challenges to studying cognition in a social setting, ultimately increasing validity and improving the welfare of the primates we study.

Chimpanzees' responses to the dead body of a 9-year-old group member

The social behavior of chimpanzees has been extensively studied, yet not much is known about how they behave in response to the death of a group member. Here, we provide a detailed report of the reactions of a group of chimpanzees to finding the dead body of a 9-year-old male group member. The behavior of the group was characterized by quiet attendance and close inspections punctuated by rare displays. Moreover, the body was continuously attended and closely inspected by several adults and juveniles, including an adult male who formed a close social bond with the deceased individual after the deceased individual's mother died 4 years earlier. When considered with observations of how chimpanzees respond to dead infants and adults in this group and in others, these observations suggest that chimpanzees' responses to death may be mediated by social bonds with the deceased individual. The results are discussed in light of recent reports on chimpanzees' reactions to dead community members and more general primate thanatology. Am. J. Primatol. 78:914-922, 2016. © 2016 Wiley Periodicals, Inc.

Hierarchy is Detrimental for Human Cooperation

Studies of animal behavior consistently demonstrate that the social environment impacts cooperation, yet the effect of social dynamics has been largely excluded from studies of human cooperation. Here, we introduce a novel approach inspired by nonhuman primate research to address how social hierarchies impact human cooperation. Participants competed to earn hierarchy positions and then could cooperate with another individual in the hierarchy by investing in a common effort. Cooperation was achieved if the combined investments exceeded a threshold, and the higher ranked individual distributed the spoils unless control was contested by the partner. Compared to a condition lacking hierarchy, cooperation declined in the presence of a hierarchy due to a decrease in investment by lower ranked individuals. Furthermore, hierarchy was detrimental to cooperation regardless of whether it was earned or arbitrary. These findings mirror results from nonhuman primates and demonstrate that hierarchies are detrimental to cooperation. However, these results deviate from nonhuman primate findings by demonstrating that human behavior is responsive to changing hierarchical structures and suggests partnership dynamics that may improve cooperation. This work introduces a controlled way to investigate the social influences on human behavior, and demonstrates the evolutionary continuity of human behavior with other primate species.

Bonobos show limited social tolerance in a group setting: a comparison with chimpanzees and a test of the relational model

Social tolerance is a core aspect of primate social relationships with implications for the evolution of cooperation, prosociality and social learning. We measured the social tolerance of bonobos in an experiment recently validated with chimpanzees to allow for a comparative assessment of group-level tolerance, and found that the bonobo group studied here exhibited lower social tolerance on average than chimpanzees in this paradigm. Furthermore, following the Relational Model of de Waal, we investigated whether bonobos responded to an increased potential for social conflict with tolerance, conflict avoidance or conflict escalation, and found that only behaviours indicative of conflict escalation differed across conditions. Taken together, these findings contribute to the current debate over the level of social tolerance of bonobos and lend support to the position that the social tolerance of bonobos may not be notably high compared with other primates.

A group-specific arbitrary tradition in chimpanzees (Pan troglodytes)

Social learning in chimpanzees has been studied extensively and it is now widely accepted that chimpanzees have the capacity to learn from conspecifics through a multitude of mechanisms. Very few studies, however, have documented the existence of spontaneously emerged traditions in chimpanzee communities. While the rigour of experimental studies is helpful to investigate social learning mechanisms, documentation of naturally occurring traditions is necessary to understand the relevance of social learning in the real lives of animals. In this study, we report on chimpanzees spontaneously copying a seemingly non-adaptive behaviour ("grass-in-ear behaviour"). The behaviour entailed chimpanzees selecting a stiff, straw-like blade of grass, inserting the grass into one of their own ears, adjusting the position, and then leaving it in their ear during subsequent activities. Using a daily focal follow procedure, over the course of 1 year, we observed 8 (out of 12) group members engaging in this peculiar behaviour. Importantly, in the three neighbouring groups of chimpanzees (n = 82), this behaviour was only observed once, indicating that ecological factors were not determiners of the prevalence of this behaviour. These observations show that chimpanzees have a tendency to copy each other's behaviour, even when the adaptive value of the behaviour is presumably absent.

Chimpanzees (Pan troglodytes) flexibly adjust their behaviour in order to maximize payoffs, not to conform to majorities

Chimpanzees have been shown to be adept learners, both individually and socially. Yet, sometimes their conservative nature seems to hamper the flexible adoption of superior alternatives, even to the extent that they persist in using entirely ineffective strategies. In this study, we investigated chimpanzees’ behavioural flexibility in two different conditions under which social animals have been predicted to abandon personal preferences and adopt alternative strategies: i) under influence of majority demonstrations (i.e. conformity), and ii) in the presence of superior reward contingencies (i.e. maximizing payoffs). Unlike previous nonhuman primate studies, this study disentangled the concept of conformity from the tendency to maintain one’s first-learned strategy. Studying captive (n=16) and semi-wild (n=12) chimpanzees in two complementary exchange paradigms, we found that chimpanzees did not abandon their behaviour in order to match the majority, but instead remained faithful to their first-learned strategy (Study 1a and 1b). However, the chimpanzees’ fidelity to their first-learned strategy was overridden by an experimental upgrade of the profitability of the alternative strategy (Study 2). We interpret our observations in terms of chimpanzees’ relative weighing of behavioural options as a function of situation-specific trade-offs. More specifically, contrary to previous findings, chimpanzees in our study abandoned their familiar behaviour to maximize payoffs, but not to conform to a majority.

Responses of chimpanzees to cues of conspecific observation

Recent evidence has shown that humans are remarkably sensitive to artificial cues of conspecific observation when making decisions with potential social consequences. Whether similar effects are found in other great apes has not yet been investigated. We carried out two experiments in which individual chimpanzees, Pan troglodytes, took items of food from an array in the presence of either an image of a large conspecific face or a scrambled control image. In experiment 1 we compared three versions of the face image varying in size and the amount of the face displayed. In experiment 2 we compared a fourth variant of the image with more prominent coloured eyes displayed closer to the focal chimpanzee. The chimpanzees did not look at the face images significantly more than at the control images in either experiment. Although there were trends for some individuals in each experiment to be slower to take high-value food items in the face conditions, these were not consistent or robust. We suggest that the extreme human sensitivity to cues of potential conspecific observation may not be shared with chimpanzees.

•

Humans respond strongly to ‘watching eyes’, but whether chimpanzees do is unknown.

•

We investigated if chimpanzees' readiness to take food was affected by face images.

•

There was no clear evidence that subjects looked at faces more than control images.

•

Any effect of the faces on chimpanzees' decisions was weak and inconsistent.

•

Chimpanzees may not be as sensitive to cues of being watched as humans are.

Neighbouring chimpanzee communities show different preferences in social grooming behaviour

Grooming handclasp (GHC) behaviour was originally advocated as the first evidence of social culture in chimpanzees owing to the finding that some populations engaged in the behaviour and others do not. To date, however, the validity of this claim and the extent to which this social behaviour varies between groups is unclear. Here, we measured (i) variation, (ii) durability and (iii) expansion of the GHC behaviour in four chimpanzee communities that do not systematically differ in their genetic backgrounds and live in similar ecological environments. Ninety chimpanzees were studied for a total of 1029 h; 1394 GHC bouts were observed between 2010 and 2012. Critically, GHC style (defined by points of bodily contact) could be systematically linked to the chimpanzee's group identity, showed temporal consistency both within and between groups, and could not be accounted for by the arm-length differential between partners. GHC has been part of the behavioural repertoire of the chimpanzees under study for more than 9 years (surpassing durability criterion) and spread across generations (surpassing expansion criterion). These results strongly indicate that chimpanzees' social behaviour is not only motivated by innate predispositions and individual inclinations, but may also be partly cultural in nature.

Variation in oxytocin is related to variation in affiliative behavior in monogamous, pairbonded tamarins

Oxytocin plays an important role in monogamous pairbonded female voles, but not in polygamous voles. Here we examined a socially monogamous cooperatively breeding primate where both sexes share in parental care and territory defense for within species variation in behavior and female and male oxytocin levels in 14 pairs of cotton-top tamarins (Saguinus oedipus). In order to obtain a stable chronic assessment of hormones and behavior, we observed behavior and collected urinary hormonal samples across the tamarins' 3-week ovulatory cycle. We found similar levels of urinary oxytocin in both sexes. However, basal urinary oxytocin levels varied 10-fold across pairs and pair-mates displayed similar oxytocin levels. Affiliative behavior (contact, grooming, sex) also varied greatly across the sample and explained more than half the variance in pair oxytocin levels. The variables accounting for variation in oxytocin levels differed by sex. Mutual contact and grooming explained most of the variance in female oxytocin levels, whereas sexual behavior explained most of the variance in male oxytocin levels. The initiation of contact by males and solicitation of sex by females were related to increased levels of oxytocin in both. This study demonstrates within-species variation in oxytocin that is directly related to levels of affiliative and sexual behavior. However, different behavioral mechanisms influence oxytocin levels in males and females and a strong pair relationship (as indexed by high levels of oxytocin) may require the activation of appropriate mechanisms for both sexes.

Prosocial behaviour emerges independent of reciprocity in cottontop tamarins

The cooperative breeding hypothesis posits that cooperatively breeding species are motivated to act prosocially, that is, to behave in ways that provide benefits to others, and that cooperative breeding has played a central role in the evolution of human prosociality. However, investigations of prosocial behaviour in cooperative breeders have produced varying results and the mechanisms contributing to this variation are unknown. We investigated whether reciprocity would facilitate prosocial behaviour among cottontop tamarins, a cooperatively breeding primate species likely to engage in reciprocal altruism, by comparing the number of food rewards transferred to partners who had either immediately previously provided or denied rewards to the subject. Subjects were also tested in a non-social control condition. Overall, results indicated that reciprocity increased food transfers. However, temporal analyses revealed that when the tamarins' behaviour was evaluated in relation to the non-social control, results were best explained by (i) an initial depression in the transfer of rewards to partners who recently denied rewards, and (ii) a prosocial effect that emerged late in sessions independent of reciprocity. These results support the cooperative breeding hypothesis, but suggest a minimal role for positive reciprocity, and emphasize the importance of investigating proximate temporal mechanisms underlying prosocial behaviour.

Cooperatively breeding cottontop tamarins (Saguinus oedipus) do not donate rewards to their long-term mates

This study tested the hypothesis that cooperative breeding facilitates the emergence of prosocial behavior by presenting cottontop tamarins (Saguinus oedipus) with the option to provide food rewards to pair-bonded mates. In Experiment 1, tamarins could provide rewards to mates at no additional cost while obtaining rewards for themselves. Contrary to the hypothesis, tamarins did not demonstrate a preference to donate rewards, behaving similar to chimpanzees in previous studies. In Experiment 2, the authors eliminated rewards for the donor for a stricter test of prosocial behavior, while reducing separation distress and food preoccupation. Again, the authors found no evidence for a donation preference. Furthermore, tamarins were significantly less likely to deliver rewards to mates when the mate displayed interest in the reward. The results of this study contrast with those recently reported for cooperatively breeding common marmosets, and indicate that prosocial preferences in a food donation task do not emerge in all cooperative breeders. In previous studies, cottontop tamarins have cooperated and reciprocated to obtain food rewards; the current findings sharpen understanding of the boundaries of cottontop tamarins' food-provisioning behavior.

The Effects of Unequal Reward Distributions on Cooperative Problem Solving by Cottontop Tamarins (Saguinus oedipus)

Cooperation among non-human animals has been the topic of much theoretical and empirical research, but few studies have examined systematically the effects of various reward payoffs on cooperative behaviour. Here, we presented heterosexual pairs of cooperatively breeding cottontop tamarins with a cooperative problem solving task. In a series of four experiments, we examined how the tamarins' cooperative performance changed under conditions in which (a) both actors were mutually rewarded, (b) both actors were rewarded reciprocally across days, (c) both actors competed for a monopolizable reward and (d) one actor repeatedly delivered a single reward to the other actor. The tamarins demonstrated sensitivity to the reward structure, exhibiting the greatest percentage of trials solved and shortest latency to solve the task in the mutual reward experiment and the lowest percentage of trials solved and longest latency to solve the task in the experiment in which one actor was repeatedly rewarded. However, even in the experiment in which the fewest trials were solved, the tamarins still solved 46 +/- 12% of trials and little to no aggression was observed among partners following inequitable reward distributions. The tamarins did, however, exhibit selfish motivation in each of the experiments. Nevertheless, in all experiments, unrewarded individuals continued to cooperate and procure rewards for their social partners.

Cooperative problem solving in a cooperatively breeding primate (Saguinus oedipus)

We investigated cooperative problem solving in unrelated pairs of the cooperatively breeding cottontop tamarin, Saguinus oedipus, to assess the cognitive basis of cooperative behaviour in this species and to compare abilities with other apes and monkeys. A transparent apparatus was used that required extension of two handles at opposite ends of the apparatus for access to rewards. Resistance was applied to both handles so that two tamarins had to act simultaneously in order to receive rewards. In contrast to several previous studies of cooperation, both tamarins received rewards as a result of simultaneous pulling. The results from two experiments indicated that the cottontop tamarins (1) had a much higher success rate and efficiency of pulling than many of the other species previously studied, (2) adjusted pulling behaviour to the presence or absence of a partner, and (3) spontaneously developed sustained pulling techniques to solve the task. These findings suggest that cottontop tamarins understand the role of the partner in this cooperative task, a cognitive ability widely ascribed only to great apes. The cooperative social system of tamarins, the intuitive design of the apparatus, and the provision of rewards to both participants may explain the performance of the tamarins.

Can media advocacy influence newspaper coverage of tobacco: measuring the effectiveness of the American stop smoking intervention study's (ASSIST) media advocacy strategies

OBJECTIVE

To compare the rate and slant of local tobacco control print media coverage in ASSIST (American stop smoking intervention study) states as compared with non-ASSIST states.

METHODS

Local tobacco control policy articles, editorials, and letters to the editors published from 1994 to 1998 clipped from all daily local newspapers in the USA were analysed (n = 95 911). The main hypothesis tested for the existence of an interaction between ASSIST intervention and time. This interaction would represent a change in the difference between ASSIST and non-ASSIST states over the course of the intervention.

RESULTS

No evidence of an ASSIST-year interaction was found. However, a main effect for ASSIST was significant for the percentage of articles with the model predicting higher rates of articles for ASSIST states. Similarly the rate of letters to the editor expressing protobacco control views was higher in ASSIST states than non-ASSIST states. No main effects or interactions were found for analyses of percentage of protobacco control editorials. Models controlled for a measure of preintervention tobacco control conditions at baseline.

CONCLUSIONS

The presence of an ASSIST main effect should be interpreted with caution because of the quasi-experimental design and the lack of information on article rates before the ASSIST intervention. Nonetheless, these preliminary findings suggest some possible effects of the media advocacy activities of ASSIST when controlling for differences in states' initial tobacco control conditions.

Evaluating the impact of population changes in diet, physical activity, and weight status on population risk for colon cancer (United States)

OBJECTIVE

To estimate the effects of observed population-level changes in risk factors on population risk and incidence of disease.

METHODS

Trends in a set of risk factors for colon cancer (vegetable intake, red meat intake, alcohol consumption, physical activity levels, and weight status) were modeled for the US adult population over the years 1975-1995 and combined with relative risk estimates from epidemiologic studies and a probability distribution for the induction period to estimate the percentage change in incidence rates from 1985 to 1995 due to the five risk factors. A sensitivity analysis was performed to account for imprecision related to estimates of trends in behavior and epidemiologic risk.

RESULTS

Increased vegetable intake and decreased intakes of red meat and alcohol reduced risk, while reduced physical activity and increased body mass index increased risk for colon cancer. When all five factors were considered together, change in the average population relative risk was small and the risk factors accounted for little of the recently observed decline in incidence.

CONCLUSIONS

Although these factors have the potential to greatly affect risk of colon cancer and incidence rates, little of that potential was realized since adverse trends neutralized what progress had been made in the areas of vegetables, red meat, and alcohol consumption.

Bayesian monitoring of a phase 2 chemoprevention trial in high-risk cohorts for prostate cancer

The objective of phase 2 cancer chemoprevention trials is to evaluate whether a chemopreventive agent will cause significant modulation of intermediate endpoint biomarkers (IEB) in patients at high risk for the disease. A phase 2 chemoprevention trial of 4-hydroxyphenyl retinamide (4-HPR) versus placebo was conducted in men with a histologic diagnosis of early prostate cancer and scheduled to have radical prostatectomy. A Bayesian monitoring method was used to sequentially monitor this trial for evidence of biological activity or ineffectiveness based on a single IEB variable. Different prior distributions were used and posterior distributions were obtained to calculate the probability that treatment differences are greater than or less than a predetermined clinically significant effect. The interim analysis of transforming growth factor-alpha expression indicated a high probability of insufficient biological activity of 4-HPR on this IEB. This study demonstrates the potential utility of Bayesian methods in the decision-making process in the conduct of phase 2 chemoprevention trials.

Cumulative cause-specific mortality for cancer patients in the presence of other causes: a crude analogue of relative survival

A common population-based cancer progress measure for net survival (survival in the absence of other causes) of cancer patients is relative survival. Relative survival is defined as the ratio of a population of observed survivors in a cohort of cancer patients to the proportion of expected survivors in a comparable set of cancer-free individuals in the general public, thus giving a measure of excess mortality due to cancer. Relative survival was originally designed to address the question of whether or not there is evidence that patients have been cured. It has proven to be a useful survival measure in several areas, including the evaluation of cancer control efforts and the application of cure models. However, it is not representative of the actual survival patterns observed in a cohort of cancer patients. This paper suggests a measure for cumulative crude (in the presence of other causes) cause-specific probability of death for a population diagnosed with cancer. The measure does not use cause of death information which can be unreliable for population cancer registries. Point estimates and variances are derived for crude cause-specific probability of death using relative survival instead of cause of death information. Examples are given for men diagnosed with localized prostate cancer over the age of 70 and women diagnosed with regional breast cancer using Surveillance, Epidemiology and End Results (SEER) Program data. The examples emphasize the differences in crude and net mortality measures and suggest areas where a crude measure is more informative. Estimates of this type are especially important for older patients as new screening modalities detect cancers earlier and choice of treatment or even 'watchful waiting' become viable options. Published in 2000 by John Wiley & Sons, Ltd.

Bayesian monitoring of phase II trials in cancer chemoprevention

Early randomized Phase II cancer chemoprevention trials which assess short-term biological activity are critical to the decision process to advance to late Phase II/Phase III trials. We have adapted published Bayesian interim analysis methods (Spiegelhalter et al., J. R. Statist. Soc A, 1994; 157: 357-416) which give greater flexibility and simplicity of inference to the monitoring of randomized controlled Phase II trials using intermediate endpoints. The Bayesian stopping rule is designed to stop the trial more quickly when the evidence suggests ineffectiveness rather than when it suggests biological activity, thus allowing resources to be concentrated on those agents that show the most promise in this early stage of testing. We investigate frequentist performance characteristics of the proposed method through simulation of randomized placebo controlled trials with a growth factor intermediate end-point using mean and variance values derived from the literature. Simulation results show expected error rates and trial size similar to other commonly used group sequential methods for this setting. These results suggest that the Bayesian approach to interim analysis is well suited for monitoring small randomized controlled Phase II chemoprevention trials for early detection of either inactive or promising agents.

Cancer surveillance series: interpreting trends in prostate cancer--part III: Quantifying the link between population prostate-specific antigen testing and recent declines in prostate cancer mortality

BACKGROUND

The objective of this study was to investigate the circumstances under which dissemination of prostate-specific antigen (PSA) testing, beginning in 1988, could plausibly explain the declines in prostate cancer mortality observed from 1992 through 1994.

METHODS

We developed a computer simulation model by use of information on population-based PSA testing patterns, cancer detection rates, average lead time (the time by which diagnosis is advanced by screening), and projected decreased risk of death associated with early diagnosis of prostate cancer through PSA testing. The model provides estimates of the number of deaths prevented by PSA testing for the 7-year period from 1988 through 1994 and projects what prostate cancer mortality for these years would have been in the absence of PSA testing.

RESULTS

Results were generated by assuming a level of screening efficacy similar to that hypothesized for the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Under this assumption, the projected mortality in the absence of PSA testing continued the increasing trend observed before 1991 only when it was assumed that the mean lead time was 3 years or less. Projected mortality trends in the absence of PSA screening were not consistent with pre-1991 increasing trends for lead times of 5 years and 7 years.

CONCLUSIONS

When screening is assumed to be at least as efficacious as hypothesized in the PLCO trial, it is unlikely that the entire decline in prostate cancer mortality can be explained by PSA testing based on current beliefs concerning lead time. Only very short lead times would produce a decline in mortality of the magnitude that has been observed.

Assessing uncertainty in microsimulation modelling with application to cancer screening interventions

Microsimulation is fast becoming the approach of choice for modelling and analysing complex processes in the absence of mathematical tractability. While this approach has been developed and promoted in engineering contexts for some time, it has more recently found a place in the mainstream of the study of chronic disease interventions such as cancer screening. The construction of a simulation model requires the specification of a model structure and sets of parameter values, both of which may have a considerable amount of uncertainty associated with them. This uncertainty is rarely quantified when reporting micro-simulation results. We suggest a Bayesian approach and assume a parametric probability distribution to mathematically express the uncertainty related to model parameters. First, we design a simulation experiment to achieve good coverage of the parameter space. Second, we model a response surface for the outcome of interest as a function of the model parameters using the simulation results. Third, we summarize the variability in the outcome of interest, including variation due to parameter uncertainty, using the response surface in combination with parameter probability distributions. We illustrate the proposed method with an application of a microsimulator designed to investigate the effect of prostate specific antigen (PSA) screening on prostate cancer mortality rates.

Case-control studies of cancer screening: theory and practice

This review summarizes methodologic theories for the design of cancer screening case-control studies and examines the methods applied in studies published in English from 1980 through 1996. In addition to summarizing state-of-the-art methodologic approaches, we identify areas where obvious gaps exist between theory and practice, and we recommend potential areas where theory and methodology may need further development. In particular, we focus on three major areas: 1) the selection of case and control subjects, 2) the definition of exposure (i.e., exposure to the screening test), and 3) bias. Each area is considered carefully by summarizing current theory, reviewing cancer screening applications, and linking recommended methodologic approaches to those used in practice to identify areas where inconsistencies exist. In general, we found methodologic theory and practice in this field of research to be consistent. However, discrepancies were identified in the area of exposure definition, including the use of screening frequency and the use of a detectable, curable preclinical phase for case subjects as the exposure measures. Even when recommended methods were followed, a number of difficulties arose in practice. Specific concerns included the ability to carry out the following: identifying all case subjects within a source population, defining eligibility criteria to ensure that case and control subjects had equal access to screening during the exposure period, distinguishing between symptomatic and diagnostic tests, and controlling for self-selection bias. Careful scrutiny is warranted in all aspects of the design of cancer screening case-control studies, and caution is advised in the interpretation of study results.

Teaching mending skills to mentally retarded adolescents

This experiment presents a model for analyzing community living skills and teaching them to mentally retarded adolescents. A task analysis of three mending skills was developed and validated, aided by consultation with persons having expertise in home economics and mental retardation. The task analysis was modified to compensate for the constraints imposed by the trainees' disabilities. Five moderately retarded youths received training on sewing hems, buttons, and seams. Sewing skills were acquired rapidly and maintained. The behavior generalized from trained to untrained tasks on their common components for all subjects. A multiple baseline across participants combined with a multiple baseline across responses demonstrated the combined effectiveness of an objectively validated, detailed task analysis; graduated sequence of prompts; and response consequences in training and maintaining community living skills with mentally retarded adolescents.