Search

Gestures play an essential role in primate communication. However, little is known about how complexity of gestural use (in terms of repertoire size, intentional use, flexibility and use of gestural sequences) relates to individual and dyadic measures of sociality and whether more complex gestural use is more effective in eliciting a response. We observed 19 captive chimpanzees (

Innovation is the ability to solve new problems or find novel solutions to familiar problems, and it is known to provide animals with crucial fitness benefits. Although this ability has been extensively studied in some taxa, the factors that predict innovation within and across species are still largely unclear. In this study, we used a novel foraging task to test 111 individuals belonging to 13 ungulate species—a still understudied taxon. To solve the task, individuals had to open transparent and opaque cups with food rewards, by removing their cover. We assessed whether individual factors (neophobia, social integration, sex, age, rank) and socio-ecological factors (dietary breadth, fission–fusion dynamics, domestication, group size) predicted participation and performance in the task. Using a phylogenetic approach, we showed that success was higher for less neophobic and socially less integrated individuals. Moreover, less neophobic individuals, individuals of domesticated species and having higher fission–fusion dynamics were more likely to participate in the task. These results are in line with recent literature suggesting a central role of sociality and personality traits to successfully deal with novel challenges, and confirm ungulates as a promising taxon to test evolutionary theories with a comparative approach.

Forest loss due to anthropogenic activities is one of the main causes of plant and animal species decline. Studying the species’ population status (i.e., density, abundance, and geographic distribution) on a regular basis is one of the main tools to assess the effect of anthropogenic activities on wildlife, to monitor population dynamics and to intervene with effective conservation strategies when the population of an endangered species declines. On Sulawesi Island, Indonesia, anthropogenic activities, such as agriculture, are decreasing the remaining natural habitats available for several endemic and endangered species. The effect of this forest loss on the threatened moor macaques (Macaca maura) in South Sulawesi is unknown, and data on the population status of this species are needed to design effective conservation strategies. To assess the population status of the moor macaques, we walked linear transects (N = 29, survey effort = 114 km) at six sites between November 2019 and March 2020 to estimate macaque population density and encounter rate. We tested the effect of anthropogenic activities on macaque encounter rate. Our global density estimate (24 individuals/km2) was lower than the overall estimate from the most detailed survey conducted on this species, which covered its whole geographic distribution (36.1 individuals/km2). However, these results should be interpreted with caution because the previous density estimate falls within the confidence intervals of our estimate. Furthermore, we found regional declines in moor macaque encounter rates in at least two sites compared with previous studies. We found a high presence of anthropogenic activity in the forests inhabited by macaques. Moor macaques were less abundant in open areas with no forest (i.e., clear cuttings) than in forested areas, and in the presence of nonspecies-specific hunting traps (i.e., wire-loop traps). Moreover, moor macaques were more abundant in areas with a higher presence of humans and domestic animals. Overall, our data suggest that the population of this species may be declining in certain regions but further surveys are needed to corroborate whether this is occurring across the entire geographic distribution.

Flexibility is an important hallmark of complex communication systems, yet few studies have systematically assessed it in non-human species. In this study, we investigated different aspects of flexibility in the gestural communication systems of 7 groups of captive apes (N = 53), including 19 chimpanzees (Pan troglodytes), 16 Sumatran orangutans (Pongo abelii) and 18 siamangs (Symphalangus syndactylus). We operationalized flexibility in four different ways: (i) the use of one gesture type across several contexts (i.e. contextual flexibility), (ii) the use of many gesture types in the same context, (iii) morphological variation with which individual gesture types can be produced (i.e. morphological flexibility), and (iv) the ability to combine signals into different sequences. Comparisons across individuals and species revealed variation in contextual and morphological flexibility. In particular, contextual flexibility increased through age, and it was overall higher in chimpanzees than in siamangs. However, morphological flexibility was highest in siamangs and lowest in orangutans. Overall, variation could be largely explained in terms of changes in social experience and differences in the socio-ecological characteristics of the species. Our findings suggest that contextual and morphological flexibility might be good candidates to study inter-individual and inter-specific variation in primate gestural production.

Human mothers interact with their infants in different ways. In Western, educated, industrialized, rich and democratic (WEIRD) societies, face-to-face interactions and mutual gazes are especially frequent, yet little is known about their developmental trajectories and if they differ from those of other primates. Using a cross-species developmental approach, we compared mother–infant interactions in 10 dyads of urban humans from a WEIRD society ( Homo sapiens ) and 10 dyads of captive zoo-based chimpanzees ( Pan troglodytes ), when infants were one, six and 12 months old. Results showed that face-to-face interactions with mutual gaze events were common in both groups throughout the infant's first year of life. The developmental trajectories of maternal and infants’ looks partially differed between species, but mutual gaze events were overall longer in humans than in chimpanzees. Mutual gazes were also more frequent in humans, peaking at six months in humans, while increasing with age in chimpanzees. The duration and frequency of mutual gazes varied across contexts in both groups, with mutual gazes being longer during caring/grooming and feeding contexts. These findings confirm that some aspects of early socio-cognitive development are shared by humans and other primates, and highlight the importance of combining developmental and cross-species approaches to better understand the evolutionary roots of parenting behaviour. This article is part of a discussion meeting issue ‘Face2face: advancing the science of social interaction’.

Gestures play a central role in the communication systems of several species, including primates. In this study, we provide a first assessment of the gestural systems of a Platyrrhine species, Geoffroy’s spider monkeys (Ateles geoffroyi). We observed a wild group of 52 spider monkeys, and assessed the distribution of visual and tactile gestures in the group, the size of individual repertoires, and the intentionality and effectiveness of individuals’ gestural production. Our results showed that younger spider monkeys were more likely than older ones to use tactile gestures, despite no inter-individual differences in the distribution of visual gestures. Repertoire size did not vary with age, whereas the probability of accounting for recipients’ attentional state was higher for older monkeys than for younger ones, especially for gestures in the visual modality. Using vocalizations right before the gesture increased the probability of gesturing toward attentive recipients and of receiving a response, although age had no effect on the probability of gestures being responded. Overall, our study provides first evidence of complex gestural communication in a Platyrrhine species, and confirms this taxon as a valid candidate for research on animal communication.

Behavioural contagion is a widespread phenomenon in animal species, which is thought to promote coordination and group cohesion. Among non-human primates, however, evidence of behavioural contagion is currently limited to few Catarrhine species. Here, we investigated whether behavioural contagion is also present in Platyrrhines (i.e. primates from South and Central America), by assessing yawning and scratching contagion in a wild group (N = 49) of Geoffroy’s spider monkeys (Ateles geoffroyi). We conducted focal samples to examine whether individuals observing the triggering event (i.e. a naturally occurring yawning or scratching event in the group) would be more likely to yawn or scratch in the following three minutes, as compared to individuals who did not observe the triggering event. We ran generalized linear mixed models using a Bayesian approach, and found that the probability of yawning and scratching was higher for individuals observing others yawning and scratching, respectively, as compared to individuals who did not observe such an event. However, behavioural contagion did not vary depending on the observer’s sex, kinship or relationship quality with the individual performing the triggering event. These findings provide the first evidence for yawning and scratching contagion in a wild group of spider monkeys, and importantly contribute to the debate about the evolutionary origins of behavioural contagion in primates, which is likely to have emerged before the evolutionary split between Platyrrhines and Catarrhines.

Before claiming major differences between the communication systems of humans and other species, it is necessary to (1) overcome methodological limitations in the comparative study of communicative intentions; (2) account for mechanisms other than epistemic vigilance that may also sustain complex forms of communication; and (3) better differentiate between motivational and cognitive factors potentially affecting the emergence of open-ended communication.

Gestural communication is crucial for primates. However, little is known about how gestural repertoires emerge through development. We conducted behavioural observations on captive apes, including 18 siamangs (Symphalangus syndactylus), 16 Sumatran orangutans (Pongo abelii), and 19 chimpanzees (Pan troglodytes), to test different hypotheses for the emergence of gestures (i.e., Phylogenetic Ritualization, Ontogenetic Ritualization, Social Negotiation, and Social Transmission hypotheses). Our results showed little variation in individual gestural repertories, and only one idiosyncratic gesture. Moreover, across subjects (N = 53), repertoire size did not increase with age and social centrality. When comparing repertoires across all possible combinations of conspecifics, including apes in different groups (N=273) for the four groups of siamangs and the two of orangutans, repertoire similarity was higher in dyads of the same group than of different groups, but it also increased with more observational effort and lower age difference between group members. Finally, when comparing repertoires across all dyads of conspecifics in the same group (N = 260), we found no differences in repertoire similarity depending on dyadic relationship quality. Overall, these results provide support for the Phylogenetic Ritualization hypothesis, according to which individuals are endowed with complete gestural repertories from birth. These repertoires are largely similar across individuals and groups, although they may be partially refined through social experiences.

Female primates represent the most important social partner for their developing offspring. However, mothers may strongly differ in the way they relate to their offspring (e.g., in terms of two different dimensions: protectiveness and rejection). In this study, we aimed to assess how dominance style predicts (i) changes in maternal behavior through offspring development, and (ii) the link between maternal behavior and offspring behavior. We conducted behavioral observations on 34 free-ranging immatures of two species of macaques with different dominance styles: less tolerant Japanese macaques (JM; Macaca fuscata) and more tolerant moor macaques (MM; Macaca maura). Our results showed that maternal behavior differed between JM and MM: maternal proximity and grooming decreased through offspring development more quickly in MM than in JM, whereas maternal rejection and aggression, which were generally more frequent in JM, decreased with offspring age similarly in both species. In contrast, maternal restraint of offspring decreased similarly with offspring age in both species. Furthermore, dominance style was differentially associated with the link between maternal and offspring behavior: in MM only, maternal grooming predicted an increase of the probability that offspring interacted with partners other than their mothers and engaged in solitary play, whereas maternal rejection predicted a decrease in the occurrence of solitary play. Overall, these results suggest interspecific variation in maternal behavior during offspring's first years of life, and point to the possibility that these differences may have an important role in shaping their behavioral development.

Gestures play an essential role in primate communication. However, little is known about how complexity of gestural use (in terms of repertoire size, intentional use, flexibility and use of gestural sequences) relates to individual and dyadic measures of sociality and whether more complex gestural use is more effective in eliciting a response. We observed 19 captive chimpanzees ( Pan troglodytes ), 16 Sumatran orangutans ( Pongo abelii ) and 18 siamangs ( Symphalangus syndactylus ) to assess the complexity and effectiveness of their gestural use. We found that, beyond interspecies variation, the number of gesture types used in a dyad was higher when individuals had stronger social bonds; the probability of accounting for others' attention increased with age, especially for visual gestures; and sequences were more likely used by younger or socially less integrated individuals. In terms of effectiveness, older individuals and those using fewer sequences were more likely to be responded to, while across dyads, the probability of obtaining a response was higher when both individuals accounted for the other's attention and when they used fewer sequences. Overall, this confirms the link between sociality and complex gestural use and suggests that more complex forms of communication, at least in terms of intentional use, may be more effective at achieving communicative goals. This article is part of the theme issue ‘Cognition, communication and social bonds in primates’.

Compositionality is the ability to combine meaningful elements into new combinations with novel meanings, and it has long been considered one of the main hallmarks of human communication. However, very few studies have addressed the compositional aspects of communication in species other than humans, although a comparative approach is essential to understand the evolutionary origins of human compositionality. We review previous research on compositionality in the gestural communication systems of nonhuman primates, with a special focus on the multicomponent aspects of compositionality. We start by discussing the importance of a comparative approach to study the evolution of human language and then compare the current state of the art on compositionality in the vocal, facial, and gestural communication systems of primates and other species. We further discuss alternative approaches to study compositionality in primates, which may help overcome some of the current methodological limitations in this research area. In particular, we 1) highlight the importance of interdisciplinary tools that facilitate the statistical identification of multicomponent and multimodal combinations of signals, 2) discuss different approaches to infer the meaning of signal combinations, with a special focus on the use of contextual cues and meta-communication, and 3) discuss temporal and intentional aspects of compositionality in primates. Finally, we outline possible lines of research for future studies in this area (e.g., more consistent use of terms across research areas, use of different methodological tools and larger datasets, inclusion of developmental approaches), which might shed light into the evolutionary origins of one of the most crucial properties of human communication.

Many species, including humans, rely on an ability to differentiate between quantities to make decisions about social relationships, territories, and food. This study is the first to investigate whether giraffes (Giraffa camelopardalis) are able to select the larger of two sets of quantities in different conditions, and how size and density affect these decisions. In Task 1, we presented five captive giraffes with two sets containing a different quantity of identical foods items. In Tasks 2 and 3, we also modified the size and density of the food reward distribution. The results showed that giraffes (i) can successfully make quantity judgments following Weber's law, (ii) can reliably rely on size to maximize their food income, and (iii) are more successful when comparing sparser than denser distributions. More studies on different taxa are needed to understand whether specific selective pressures have favored the evolution of these skills in certain taxa.

Mirror self-recognition (MSR), usually considered a marker of self-awareness, occurs in several species and may reflect a capacity that has evolved in small incremental steps. In line with research on human development and building on previous research adopting a gradualist framework, we categorized the initial mirror responses of naive spider monkeys (Ateles geoffroyi) according to four levels. We compared social, exploratory, contingent and self-exploratory responses to a mirror and faux mirror during three short trials. If spider monkeys respond as most monkey species, we predicted they would perform at level 0, mainly showing social behavior toward their mirror-image. However, because spider monkeys show enhancement of certain cognitive skills comparable to those of great ape species, we predicted that they would perform at level 1a (showing exploratory behavior) or 1b (showing contingent behavior). GLMMs revealed that monkeys looked behind and visually inspected the mirror significantly more in the mirror than the faux mirror condition. Although the monkeys engaged in contingent body movements at the mirror, this trend was not significant. Strikingly, they showed no social behaviors toward their mirror-image. We also measured self-scratching as an indicator of anxiety and found no differences in frequencies of self-scratching between conditions. Therefore, in contrast to most findings on other species, spider monkeys did not treat their image as another monkey during their initial exposure to the mirror. In fact, they reached at least level 1a within minutes of mirror exposure. These responses recommend spider monkeys as good candidates for further explorations into monkey self-recognition. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Cooperative hunting is generally considered to be a cognitively challenging activity, as individuals have to coordinate movements along with a partner and at the same time react to the prey. Wolves are said to engage in cooperative hunting regularly, whereas dogs could have maintained, improved, or reduced their cooperative skills during the domestication process. We compared the performance of individuals from two wolf packs and two dog groups with similar gender and rank structure. Members of these groups were tested in dyads with a problem-solving paradigm that involved aspects of a hunting-like situation. Subjects needed to coordinate their actions in order to get food. They were confronted with a social dilemma, in which an individual benefit from being selfish, unless the partner also chooses the selfish alternative, in which case the whole dyad loses. In the task, one partner was required to draw a barrier toward it by rushing forward, allowing the other partner to access the food, at which point both partners were allowed to access the food. Most dyads could solve the problem, with significant variation in their performance but no differences between species. However, the probability of taking the risk in a dyad depended on the species and rank of the individual and on cofeeding in the dyad. The results of this study show that wolves do not always outperform dogs when coordinating their actions, but that the cooperative behavior of Canis depends on many factors, including rank, type of task, and tolerance within the dyad. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Innovation is the ability to solve novel problems or find novel solutions to familiar problems, and it is known to affect fitness in both human and non-human animals. In primates, innovation has been mostly studied in captivity, although differences in living conditions may affect individuals’ ability to innovate. Here, we tested innovation in a wild group of Barbary macaques (Macaca sylvanus). In four different conditions, we presented the group with several identical foraging boxes containing food. To understand which individual characteristics and behavioural strategies best predicted innovation rate, we measured the identity of the individuals manipulating the boxes and retrieving the food, and their behaviour during the task. Our results showed that success in the novel task was mainly affected by the experimental contingencies and the behavioural strategies used during the task. Individuals were more successful in the 1-step conditions, if they participated in more trials, showed little latency to approach the boxes and mainly manipulated functional parts of the box. In contrast, we found no effect of inhibition, social facilitation and individual characteristics like sex, age, rank, centrality, neophobia and reaction to humans, on the individuals’ ability to innovate.

With increasing anthropogenic pressure, interactions between humans and wildlife may become more frequent, including conflictual ones. To reduce conflicts, it is important to understand how different factors (e.g. education, previous experience, demographic vari-ables) interplay with each other and contribute to the emergence of negative attitudes and behaviours toward wildlife in humans. To address this issue, we conducted a large-scale questionnaire in Malaysia, focusing on potential conflicts between human and other pri-mates. We used generalized linear mixed models to assess how formal education, knowl-edge about primates, negative experience and potential competition affected participants’ negative attitudes to primates (i.e. how humans perceive primates), their behavioural inten-tions (i.e. opinion on how to reduce conflicts) and behaviour (i.e. measures taken to reduce negative interactions). We found that negative experience and potential competition had a negative impact on participants’ attitude and behavior (i.e. primates were more likely perceived as filthy, as negatively affecting residents’ health and safety, and as an increas-ing problem, with participants more likely to use invasive methods, including captures). Both higher education and better knowledge of primates predicted more positive behav-ioural intentions (i.e. primates should be protected, non-invasive interventions should be used). Higher education, however, was also linked to more negative attitudes (i.e. primates negatively affect residents’ health and safety), and partly to negative behavior (e.g. use of invasive methods). In contrast, better knowledge about primates predicted positive behav-iour (i.e. exclusive use of non-invasive methods). Therefore, although better knowledge of primates had no clear effect on human attitudes, it may impact on their decisions to reduce potential conflicts with wildlife, and might be the most powerful tool to mitigate conflicts between humans and other species

Foraging devices are effective enrichment tools for non-human primates, as they provide both cognitive and manipulative stimulation that may enhance these animals' welfare. We assessed the behavioral effects of a novel tool-based enrichment on 14 chimpanzees (Pan troglodytes) housed at Fundació Mona (Girona, Spain). The device consisted of a vertical maze filled with food rewards, which chimpanzees could extract by using tools. We conducted behavioral observations in two conditions over an approximately 2.5-month period: when the food maze was loaded (12 enrichment days), and when it was empty (12 baseline days). Data were collected using 2-min scan sampling and untimed-event focal sampling during two daily sessions of 80 min each. We expected that the chimpanzees' interest in the enrichment would decrease over time, but that its use would be linked to an increase in the occurrence of species-typical behaviors, a reduction in negative indicators of welfare, and changes in social behaviors. We found that participation widely varied among subjects, being higher in females and decreasing through time. Furthermore, participation was linked to an increase in tool use and a decrease in inactivity, but also to an increase in aggression-related behaviors. In contrast, participation had no effect on the occurrence of abnormal behaviors, social proximity or affiliation-related behaviors. Finally, we detected an increase in self-directed behaviors only when subjects actively interacted with the device. We conclude that, in future studies, these types of devices should be evaluated for longer periods of time and more attention should be paid to individuals' preferences and abilities Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This research was funded by la Caixa Foundation, grant number LCF/PR/PR17/11120020 (to MP and ML) and by Generalitat de Catalunya (2017 SGR‐1040) and Universitat Rovira i Virgili (2019PFR‐URV91) (to ML)

When studying animal behavior in the wild, some behaviors may require observation from a relatively short distance. In these cases, habituation is commonly used to ensure that animals do not perceive researchers as a direct threat and do not alter their behavior in their presence. However, habituation can have significant effects on the welfare and conservation of the animals. Studying how nonhuman primates react to the process of habituation can help to identify the factors that affect habituation and implement habituation protocols that allow other researchers to speed up the process while maintaining high standards of health and safety for both animals and researchers. In this study, we systematically described the habituation of two groups of wild moor macaques (Macaca maura), an Endangered endemic species of Sulawesi Island (Indonesia), to assess the factors that facilitate habituation and reduce impact on animal behavior during this process. During 7 months, we conducted behavioral observations for more than 7,872 encounters and an average of 120 days to monitor how macaque behavior toward researchers changed through time in the two groups under different conditions. We found that both study groups (N = 56, N = 41) became more tolerant to the presence of researchers during the course of the habituation, with occurrence of neutral group responses increasing, and minimum distance to researchers and occurrence of fearful group responses decreasing through time. These changes in behavior were predominant when macaques were in trees, with better visibility conditions, when researchers maintained a longer minimum distance to macaques and, unexpectedly, by the presence of more than one researcher. By identifying these factors, we contribute to designing habituation protocols that decrease the likelihood of fearful responses and might reduce the stress experienced during this process.

Anthropogenic pressure has significantly increased in the last decades, often enhancing conflicts at the human–wildlife interface. Therefore, understanding peoples’ value orientations, attitudes and behavioural intentions towards wildlife is a crucial endeavour to reduce the occurrence of conflicts between humans and wildlife. Previous research in the USA has shown a consistent link between modernization and increased anthropomorphism (i.e., the tendency to attribute human mental or physical characteristics to other entities), leading to positive changes in value orientations, attitudes, and behavioural intentions towards wildlife. In this paper, we aimed to address whether this link is also present in other cultures, by testing participants (N = 741) in five different countries (Brazil, Indonesia, Malaysia, Mexico, and Spain). Our study shows that while the positive link between anthropomorphism, positive attitudes and behavioural intentions towards wildlife is universal, the link between modernization and anthropomorphism is culturally mediated. In some countries (Indonesia, Malaysia, Spain), modernization increased anthropomorphism, while in others modernization predicted no differences (Brazil) or even a decrease in anthropomorphism (Mexico), ultimately deteriorating individuals’ attitude and behavioural intentions towards wildlife. These results call for caution when generalizing findings from western industrialized countries to inform conservation policies worldwide.

Simple Summary The welfare of captive animals is nowadays a topic of major concern. In order to express their natural behavioral repertoires, however, animals require complex environments and stimuli which are difficult to reproduce in captivity. To overcome this, environmental enrichment is considered one of the most successful tools to increase behavioral opportunities and enhance animal welfare. In this study, we explored whether providing an artificial termite-fishing task, and whether participation in this task, predicted changes in the solitary and social behavior of sanctuary-housed chimpanzees (Pan troglodytes). We compared chimpanzee behavior when the enrichment was presented to different periods without enrichment. We found that the presence of the enrichment predicted an increase in tool use and feeding behavior and a decrease in inactivity, especially for those chimpanzees with higher participation. However, we did not detect significant changes in abnormal or self-directed behaviors. Furthermore, we found no variation in affiliation- or aggression-related behaviors, but social proximity increased in chimpanzees that participated more. Our results support previous studies demonstrating that artificial termite-fishing promotes species-typical behaviors in captive chimpanzees with no major effects on social activities. Abstract Artificial termite-fishing tasks are a common enrichment for captive great apes, promoting species-typical behaviors. Nonetheless, whether these activities are linked to changes in other behaviors and whether these changes persist over time has seldom been investigated. We assessed whether the use of an artificial termite-fishing task was linked to changes in the solitary behavior and social dynamics in two groups of sanctuary-housed chimpanzees (Pan troglodytes). Specifically, we compared chimpanzee behavior during eight enrichment sessions distributed over a two-month period, with similar periods before and after the introduction of the enrichment. Data were collected from combined interval and continuous sampling methods and were analyzed using generalized linear mixed models. We found that participation increased across sessions and that both enrichment and participation predicted an increase in tool use and feeding and a decrease in inactivity, which were all maintained throughout the sessions. Furthermore, participation was positively associated with social proximity, revealing a gathering effect of the task. However, neither enrichment nor participation were linked to changes in abnormal, self-directed, affiliation-related or aggression-related behaviors. Overall, our results support the hypothesis that artificial termite-fishing is a suitable enrichment for captive chimpanzees, maintaining the subjects’ interest and promoting species-typical behaviors, with no negative effects on social activities.

Inter-specific emotion recognition is especially adaptive when species spend a long time in close association, like dogs and humans. Here, we comprehensively studied the human ability to recognize facial expressions associated with dog emotions (hereafter, emotions). Participants were presented with pictures of dogs, humans and chimpanzees, showing angry, fearful, happy, neutral and sad emotions, and had to assess which emotion was shown, and the context in which the picture had been taken. Participants were recruited among children and adults with different levels of general experience with dogs, resulting from different personal (i.e. dog ownership) and cultural experiences (i.e. growing up or being exposed to a cultural milieu in which dogs are highly valued and integrated in human lives). Our results showed that some dog emotions such as anger and happiness are recognized from early on, independently of experience. However, the ability to recognize dog emotions is mainly acquired through experience. In adults, the probability of recognizing dog emotions was higher for participants grown up in a cultural milieu with a positive attitude toward dogs, which may result in different passive exposure, interest or inclination toward this species. Methods - Participants - Materials - Procedures - Statistics Results - Model 1 - Children - Model 2 - Adults - Speraman exact tests Discussion