Natal Attraction in Adult Female Baboons (Papio cynocephalus ursinus) in the Moremi Reserve, Botswana

Mammalian females are strongly attracted to infants and interact regularly with them. Female baboons make persistent attempts to touch, nuzzle, smell and inspect other females’ infants, but do not hold them for long periods, carry them, or provide other kinds of care for them. Mothers generally tolerate these interactions, but never initiate them. The function of these brief alloparental interactions is not well understood. Infant handling might be a form of reproductive competition if females’ interest in infants causes distress to mothers or harm to their infants. Alternatively, infant handling might be the product of selection for appropriate maternal care if females who are highly responsive to infants are the most successful mothers. We test several predictions derived from these hypotheses with data collected in a free‐ranging group of baboons (Papio cynocephalus ursinus) in the Moremi Reserve of Botswana. Infants were most attractive when they were very young. Mothers of young infants were approached by other adult females on average once every 6 min, and other females attempted to handle their infants approximately once every 9 min. By the time infants were a year old, their mothers were being approached only once every 30 min and infants were being handled only once every 5 h. Females were more strongly attracted to other females’ infants when they had young infants of their own, and their interest in other females’ infants declined as their own infants matured. Females seemed to be equally attracted to all infants, but had greater access to offspring of their relatives and subordinate females. Females nearly always grunted as they handled infants. As in other contexts grunts are a reliable predictive signal that non‐aggressive behavior will follow, the use of grunts before handling suggests that these interactions were not a form of deliberate harassment.     

Maternal and alloparental care in a troop of free-ranging Japanese monkeys

In four years of observation of a free-ranging Japanese monkeys, reproductive rate, physical development of infants, maternal care and alloparental care were studied. Primiparous mothers, orphanned mothers and old mothers showed different types of maternal care from typical multiparous mothers, and the reproductive success of each of these categories of mother also differed. Among nulliparae, 2-year-old females showed the most interest in infants. Adult females were generally indifferent to other females' infants and came to act aggressively toward them with increasing age and maternal experience.     

Alloparental behavior in a captive group of spider monkeys (Ateles geoffroyi) at the Auckland zoo

I studied alloparental behavior in a captive group of spider monkeys at the Auckland Zoo using seven infants as focal subjects and assessed the effects of age, sex, and reproductive status of alloparents on patterns of infant-other interaction. Adult males initiated interactions with infants most often, followed by adult females. Immature individuals interacted with infants infrequently. Infants themselves initiated contact with adult males more often than with other members of the group. Alloparental behavior in spider monkeys differs from that in most other species in that the infant is an active rather than a passive participant in alloparental interactions. I discuss the patterns of infant-other interaction in relation to the social structure and dispersal patterns of Ateles.     

Quantitative Linking Hypotheses for Infant Eye Movements

The study of cognitive development hinges, largely, on the analysis of infant looking. But analyses of eye gaze data require the adoption of linking hypotheses: assumptions about the relationship between observed eye movements and underlying cognitive processes. We develop a general framework for constructing, testing, and comparing these hypotheses, and thus for producing new insights into early cognitive development. We first introduce the general framework – applicable to any infant gaze experiment – and then demonstrate its utility by analyzing data from a set of experiments investigating the role of attentional cues in infant learning. The new analysis uncovers significantly more structure in these data, finding evidence of learning that was not found in standard analyses and showing an unexpected relationship between cue use and learning rate. Finally, we discuss general implications for the construction and testing of quantitative linking hypotheses. MATLAB code for sample linking hypotheses can be found on the first author''s website.     

Manipulation of Infant‐Like Traits Affects Perceived Cuteness of Infant,Adult and Cat Faces

Physical traits that are characteristic of human infants are referred to as baby‐schema, and the notion that these affect perception of cuteness and elicit care giving from adults has a long history. In this study, infant‐similarity was experimentally manipulated using the difference between adult and infant faces. Human infant, human adult and cat faces were manipulated to look more (human) infant‐like or adult‐like. The results from the current study demonstrate the impact of infant‐similarity on human adults' perception of cuteness across the three different types of face. The type of face had a large impact on perceived cuteness in line with the expected infant‐similarity of the images. Infants and cats were cutest while adults were less cute. The manipulations of infant‐similarity, however, had similar effects on the perception of cuteness across all three types of face. Faces manipulated to have infant‐like traits were rated as cuter than their equivalents manipulated to have adult‐like traits. These data demonstrate that baby‐like traits have a powerful hold over human perceptions and that these effects are not simply limited to infant faces.     

Adoption in Anthropoid primates

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

Integration of a hand-reared chimpanzee (Pan troglodytes) infant into a social group of conspecifics

Rejections of infants among non-human primates occasionally occur in the wild as well as in captive settings. Controlled adoptions of orphans and introductions of individuals into new groups are therefore sometimes necessary in captivity. Consequently, behavioral research on integration procedures and on the acceptance of infants by adoptive mothers is much needed. In this study, the introduction and subsequent adoption were examined in an 18-month-old hand-reared chimpanzee (Pan troglodytes). The infant was introduced into an age/sex-diversified social group of conspecifics at Furuvik Zoo, Gävle, Sweden, and continuous focal data was collected during the final stage of integration, including infant care exhibited by the group members and the infant’s secure base behavior. The infant was successfully integrated into the group and engaged in positive social interactions with all group members. An adult primiparous female chimpanzee formed a bond resembling a mother–infant relationship with the infant, which continues to be maintained at publication. However, the female initially showed very limited interest in the infant. It was, in fact, two other younger female group members that exhibited most infant care. The infant’s secure base behavior patterns indicate that she adapted well to the new circumstances in the chimpanzee group as the integration progressed. This provides evidence that a final adopter does not necessarily initially show maternal interest and that there can be flexibility in maternal behavior in adult chimpanzee females. Moreover, the methods applied employing gradual familiarization with all the group members and the use of an integration enclosure, may have contributed to a successful result. These findings extend our knowledge of introduction procedures in captivity as well as provide information on foster mother–infant attachment in chimpanzees.     

Transport of dead infant mountain gorillas by mothers and unrelated females

This report describes prolonged carriage of the corpses of two mountain gorilla infants by both related and unrelated adult females. Two hypotheses regarding this transport are considered: 1) that maternal behavior toward unrelated infants may be a by‐product of the hormonal condition of pregnancy, and 2) that the animals may be “learning to mother,” as nulliparous females could benefit from the experience of handling an infant that is no longer alive. Some factors pertinent to the event of infant deaths in captivity are considered. Zoo Biol 23:375–378, 2004. © 2004 Wiley‐Liss, Inc.     

Preferential attention to same-and other-ethnicity infant faces does not fully overcome the other-race effect

Given the attentional and motivational saliency of infant faces, triggered by a set of perceptual baby schema features, other-ethnicity infant faces may overcome the processing differences associated with the other-race effect (ORE). Using an attentional bias paradigm, we found that while there was a same-ethnicity attentional bias for adult faces, there was no difference in attention to same- and other-ethnicity infant faces, suggesting that other-ethnicity infant faces are equally salient and not subject to the same bias as other-ethnicity adult faces. To directly measure the ORE, we used a recognition memory test to measure differences between same- and other-ethnicity infant and adult faces. Regardless of age, same-ethnicity faces were better remembered than other-ethnicity faces. Further, regardless of ethnicity, adult faces were better remembered than infant faces, a finding consistent with an Other Age Effect. Taken together, these experiments suggest that the saliency of baby schema does not fully overcome the social or perceptual factors leading to the ORE.     

Mother-offspring conflict and interference at mother's mating inMacaca fascicularis

Theory suggests that it is in the interest of an infant to garner more care than its mother is selected to provide and that a rival sibling would curtail care from the mother. Thus delayed conception in the mother would be of advantage to the infant. One method of achieving this result would be to interfere with the mother's potential matings. To test this theory, the conflict between mothers and their infants in relation to maximizing inclusive fitness has been studied inMacaca fascicularis and infant interference has been observed. Focal animal samples were taken on 8 mothers and their 13 infants. Interactions analyzed were those between the mother and (1) an adult male, (2) her infant, (3) an adult female, (4) her infant and an adult male, (5) her infant and an adult female. Only explicit behaviours were analyzed. The infant's interference was found to be significantly related to its mother's mating, and this produced a deterring effect on the male. Infants did not interfere with any female's matings other than those of their mother. The interference was related to the number of mother-male contacts. In mothers that did subsequently conceive, infant interference at mating increased up to the mother's conception date and decreased thereafter. By contrast to the infants direct method, mothers approached the conflict indirectly. There were significantly more contacts and mounts with males in their infant's absence, they reacted negatively to their infant only when it had interfered, they were more lenient in the presence of an adult female than with an adult male, and they avoided their infant's presence at mother-male contacts. No significant sex bias in interference or the number of contacts with mother-male pairs has been found. There are indications of a sibship pattern of interference.     

Attachment and Children’s Biased Attentional Processing: Evidence for the Exclusion of Attachment-Related Information

Research in both infants and adults demonstrated that attachment expectations are associated with the attentional processing of attachment-related information. However, this research suffered from methodological issues and has not been validated across ages. Employing a more ecologically valid paradigm to measure attentional processes by virtue of eye tracking, the current study tested the defensive exclusion hypothesis in late childhood. According to this hypothesis, insecurely attached children are assumed to defensively exclude attachment-related information. We hypothesized that securely attached children process attachment- related neutral and emotional information in a more open manner compared to insecurely attached children. Sixty-two children (59.7% girls, 8–12 years) completed two different tasks, while eye movements were recorded: task one presented an array of neutral faces including mother and unfamiliar women and task two presented the same with happy and angry faces. Results indicated that more securely attached children looked longer at mother’s face regardless of the emotional expression. Also, they tend to have more maintained attention to mother’s neutral face. Furthermore, more attachment avoidance was related to a reduced total viewing time of mother’s neutral, happy, and angry face. Attachment anxiety was not consistently related to the processing of mother’s face. Findings support the theoretical assumption that securely attached children have an open manner of processing all attachment-related information.     

Hormonal changes related to paternal and alloparental care in common marmosets (Callithrix jacchus)

The physiological mechanisms of parental and alloparental care in cooperatively breeding nonhuman primate species such as the common marmoset (Callithrix jacchus) are poorly known. In this study, we examined prolactin and cortisol plasma levels of fathers and older offspring of both sexes, with and without previous experience in infant carrying, around parturition and during infant carrying. Blood samples were collected from fathers and older offspring and prolactin and cortisol were measured by RIA and EIA, respectively. Prolactin levels of both caretakers were not influenced by infant's birth, previous experience or proximity to parturition. However, prolactin levels increased in both caretakers while in physical contact with infants and also with the number of infants being carried in older offspring. These findings suggest that increased prolactin seems to be mainly due to physical effort rather than a physiological trigger of paternal and alloparental care in common marmosets. Cortisol levels were higher for experienced fathers shortly before parturition which could act to reinforce affiliative bonds between breeding males and females at this time or in the ability of males to detect the proximity of the parturition or both.     

What Happens during the Stimulus Onset Asynchrony in the Dot-Probe Task? Exploring the Role of Eye Movements in the Assessment of Attentional Biases

The dot-probe paradigm is one of the most often used paradigms to investigate attentional biases towards emotional information. However, a large number of the dot-probe studies so far used a long stimulus onset asynchrony allowing for eye movements to occur, which might increase the error variance. This study aimed at addressing this methodological issue by varying the instructions with regard to the gaze behavior and calculating the reaction time (RT) bias score (i.e., RTs for targets presented at the location of the emotional compared to the neutral stimulus) separately for trials with eye movements and trials without eye movements. Results of Experiment 1 (using typical instructions, i.e., instructions that are lenient with regard to eye movements) showed an RT bias, but only in the trials without eye movements The overall RT bias (calculated “blind” for eye movements) was non-significant. In Experiment 2, stricter instructions and small changes in the procedure led to a sharp decrease in the number of eye movements, such that both the RT bias in the trials without eye movements as well as the RT bias across all trials was significant.     

Frontal EEG Activation Asymmetry Reflects Cognitive Biases in Anxiety: Evidence from an Emotional Face Stroop Task

Electroencephalography (EEG) has been extensively used in studies of the frontal asymmetry of emotion and motivation. This study investigated the midfrontal EEG activation, heart rate and skin conductance during an emotional face analog of the Stroop task, in anxious and non-anxious participants. In this task, the participants were asked to identify the expression of calm, fearful and happy faces that had either a congruent or incongruent emotion name written across them. Anxious participants displayed a cognitive bias characterized by facilitated attentional engagement with fearful faces. Fearful face trials induced greater relative right frontal activation, whereas happy face trials induced greater relative left frontal activation. Moreover, anxiety specifically modulated the magnitude of the right frontal activation to fearful faces, which also correlated with the cognitive bias. Therefore, these results show that frontal EEG activation asymmetry reflects the bias toward facilitated processing of fearful faces in anxiety.     

Affiliative relationships between adult males and immature group members in naturally occurring ringtailed lemurs (Lemur catta)

Affiliative relations between adult males and immature group members were studied in three naturally occurring groups of ringtailed lemurs (Lemur catta) over a 12-month period at Beza-Mahafaly Reserve, southwestern Madagascar. No statistically significant difference was found in rates of affiliative interactions between adult males and older immatures (juveniles and adolescents) over reproductive seasons. However, some of the adult males in two focal groups increased their rates of affiliative behaviors with older immatures during the lactation and subsequent 1993 postmigration periods. Female involvement with infants during lactation season, the increasing independence of juveniles and adolescents, and length of male tenure may be factors contributing to such a pattern. Neither adult males nor immatures were significantly responsible for the initiation and maintenance of proximity in male-immature dyadic interactions. Neither dominance rank nor age-class of the adult male affected their rates of affiliative behavior with immatures. The majority of focal males exhibited an interest in infants and occasionally participated in alloparental care. It is suggested that adult males can benefit from affiliative relations with immatures in terms of opportunities for greater spatial centrality in the group, which can lead to enhanced predator protection and greater opportunities to develop affiliative relationships with females. Immatures can benefit from affiliation with males in relation to enhanced predator detection and protection, alloparental care, and opportunities to develop social skills. Am J Phys Anthropol 103:163–171, 1997. © 1997 Wiley-Liss, Inc.     

I Can't Take My Eyes Off of You: Attentional Allocation to Infant,Child, Adolescent and Adult Faces in Mothers and Non-Mothers

It has been reported previously that infant faces elicit enhanced attentional allocation compared to adult faces in adult women, particularly when these faces are emotional and when the participants are mothers, as compared to non-mothers [1]. However, it remains unclear whether this increased salience of infant faces as compared to adult faces extends to children older than infant age, or whether infant faces have a unique capacity to elicit preferential attentional allocation compared to juvenile or adult faces. Therefore, this study investigated attentional allocation to a variety of different aged faces (infants, pre-adolescent children, adolescents, and adults) in 84 adult women, 39 of whom were mothers. Consistent with previous findings, infant faces were found to elicit greater attentional engagement compared to pre-adolescent, adolescent, or adult faces, particularly when the infants displayed distress; again, this effect was more pronounced in mothers compared to non-mothers. Pre-adolescent child faces were also found to elicit greater attentional engagement compared to adolescent and adult faces, but only when they displayed distress. No preferential attentional allocation was observed for adolescent compared to adult faces. These findings indicate that cues potentially signalling vulnerability, specifically age and sad affect, interact to engage attention. They point to a potentially important mechanism, which helps facilitate caregiving behaviour.     

Variable infant care contributions in cooperatively breeding groups of wild saddleback tamarins

Among non-human primates, alloparental infant care is most extensive in callitrichines, and is thought to be particularly costly for tamarins whose helpers may suffer increased energy expenditure, weight loss, and reduced feeding time and mobility. The costs and benefits of infant care likely vary among group members yet very few wild studies have investigated variable infant care contributions. We studied infant care over an 8-month period in four wild groups of saddleback tamarins in Bolivia to evaluate: (a) what forms of infant care are provided, by whom, and when, (b) how individuals adjust their behavior (activity, vigilance, height) while caring for infants, and (c) whether individuals differ in their infant care contributions. We found that infant carrying, food sharing, and grooming varied among groups, and immigrant males—those who joined the group after infants were conceived—participated less in infant care compared to resident males. Adult tamarins fed less, rested more, and increased vigilance while carrying infants. Although we did not detect changes in overall activity budgets between prepartum and postpartum periods, tamarins spent more time scanning their environments postpartum, potentially reflecting increased predation risk to both carriers and infants during this period. Our study provides the first quantitative data on the timing and amount of infant carrying, grooming, and food transfer contributed by all individuals within and among multiple wild groups, filling a critical knowledge gap about the factors affecting infant care, and highlighting evolutionary hypotheses for cooperative breeding in tamarins.     

Male Tibetan macaques' (Macaca thibetana) choice of infant bridging partners

Adult male Tibetan(Macaca thibetana), Barbary(M. sylvanus), and stump-tailed macaques(M. arctoides) engage in bridging, a ritualized infant-handling behavior. Previous researchers found a bias toward the use of male infants for this behavior, but its function is debated. Explanations include three hypotheses: paternal care, mating effort, and agonistic buffering. We studied a group of habituated, provisioned Tibetan macaques to test whether adult males' affiliative relationships with females predicted their use of an infant for bridging. We also examined biases for sex, age, and individual in males' choice of bridging infant. We collected data via all occurrences, focal animal, and scan methods, from August to September 2011 at the Valley of the Wild Monkeys, China. We found that male infants were significantly preferred over females for bridging, but of three male infants in the group, only one was used by all males, while one male infant was used less often than expected. Adult males had females they were significantly more likely to be proximate to and/or to groom, but these corresponded to the mother of the bridging infant for only one male. Our results are most consistent with the agonistic buffering hypothesis: lower-ranked males used the alpha male's preferred bridging infant in an attempt to regulate their interactions with the alpha.     

Allomaternal Investment and Relational Uncertainty among Ngandu Farmers of the Central African Republic

Several studies have suggested a matrilateral bias in allomaternal (non-maternal) infant and child caregiving. The bias has been associated with the allomother’s certainty of genetic relatedness, where allomothers with high certainty of genetic relatedness will invest more in children because of potential fitness benefits. Using quantitative behavioral observations collected on Ngandu 8- to 12-month-old infants from the Central African Republic, I examine who is caring for infants and test whether certainty of genetic relatedness may influence investment by allomothers. Results indicate a matrilateral bias in caregiving by extended kin members, but this does not affect the total level of care infants receive when fathers and siblings are included in the analysis. These results replicate a previous study done among an adjacent foraging population and emphasize the importance of examining children’s complete social environments when addressing caregiving and child development.     

Feature-based attention in the frontal eye field and area V4 during visual search

When we search for a target in a crowded visual scene, we often use the distinguishing features of the target, such as color or shape, to guide our attention and eye movements. To investigate the neural mechanisms of feature-based attention, we simultaneously recorded neural responses in the frontal eye field (FEF) and area V4 while monkeys performed a visual search task. The responses of cells in both areas were modulated by feature attention, independent of spatial attention, and the magnitude of response enhancement was inversely correlated with the number of saccades needed to find the target. However, an analysis of the latency of sensory and attentional influences on responses suggested that V4 provides bottom-up sensory information about stimulus features, whereas the FEF provides a top-down attentional bias toward target features that modulates sensory processing in V4 and that could be used to guide the eyes to a searched-for target.