Mother-infant and adult female choice behavior in rhesus monkeys after various rearing experiences

Social stimuli and social rewards in primate learning and cognition

Many studies have suggested that non-human primates have good individual recognition abilities, that social stimuli can serve as discriminative stimuli in learning tests and that visual access to social objects or events can be a reinforcer for operant behaviour. Intensified research efforts comparing the effectiveness of social and non-social stimuli and rewards across a range of learning and other cognitive tasks would help clarify the extent to which monkeys and apes might be specially predisposed to process information in the social domain. In addition to identity, social interactions and relationships constitute raw material to be mentally represented and processed. Some studies have addressed the individual and evolutionary origins of mechanisms underlying the ability to attribute mental states and intentions to others, for example by looking at the understanding of another's gaze, imitation and the development of tactical deception. The results of some of this research suggest that only some species might be capable of higher-order attribution. Further progress in the study of primate social cognition will require continuing refinement of methods and the development of new techniques to compare primates as behaviourists and mentalists.

Development of infant common marmosets' (Callithrix jacchus) preference for their parents over adults from another group

Parent-offspring attachment is important for animals which have offspring that require parental care for their development. Infant attachment to the mother has been examined in macaques, but it remains poorly understood in common marmosets. Here, we examined the abilities of 14 common marmoset infants to show preference for their parents over adults from another group at the ages of 4, 10, and 15 weeks. Each infant was exposed to its parent and an adult from another group in an I-shaped maze. Although 4-week-old infants did not show a significant difference between approach behaviors toward their parents and other adults, 10- and 15-week-old infants approached and stayed longer near their parents than adults from another group. These results suggest selective approach behavior develops in marmosets by the age of 10 weeks.

Toward a general theory of infantile attachment: a comparative review of aspects of the social bond

This critical appraisal of contemporary interpretations in the area of infantile attachment begins with an outline of the principal features of the Bowlby-Ainsworth ethological theory, the instrumental/operant learning theory of Gewirtz, and Hoffman's classical conditioning model. Some attention is also given to Cairns's contiguity learning analysis and the Hoffman-Solomon opponentprocess model Discussion of these theories is followed by a review of representative data from infants at four phyletic levels (precocial birds, dogs, monkeys, and human beings), with an emphasis on three aspects of social bonding: (a) the formation and persistence of social ties in the infant under conditions of maltreatment, (b) the role of the attachment object in the adjustment of the infant to the broader environment (the so-called secure base effect), and (c) the infant's reaction to involuntary separation from the attachment object.

An attempt is made to judge how well each of the interpretations accounts for all or part of the data, with the conclusion that current theories do not accord completely with documented attachment phenomena. The following criticisms are highlighted: Ethological theory emphasizes that infants' behavior systems have been shaped by the ordinarily expectable environment and depend on that environment for their functioning, yet infants of many species form bonds to objects not typical in any species' environment, or even to sources of maltreatment. Learning theory is faulted for making predictions contradicted by the maltreatment data and for a lack of formal mechanisms to account for the secure base and separation effects. The contiguity analysis is criticized for its inability to account for the emergence of certain response patterns during separation, and the opponent-process model is called into question because of its failure to fit important affective dynamics of social separation (a central focus of this theory). Recommendations for future theories of attachment are offered.

An experimental examination of female responses to infant face coloration in rhesus macaques

In many primates, infants possess distinctive coloration that changes as a function of age. This colour is thought to serve the purpose of eliciting caretaking behaviour from the mother as well as other conspecifics. The present study investigated the responses of adult female rhesus macaques (Macaca mulatta) to pictures of infant faces in relation to infant age and facial coloration. Study animals were shown digitized images of neonates and 5-6-month-old infants displaying either unaltered facial colour, pink neonatal colour, or novel (green) facial colour. While infant and neonate faces of all colours elicited the attention of adult females, pink neonatal facial coloration did not appear to be especially attractive to subjects in contrast with the findings from an earlier study [Higley, J.D., Hopkins, W.D., Hirsch, R.M. Marra, L.M. Suomi S.J., 1987. Preferences of female rhesus monkeys (Macaca mulatta) for infantile coloration. Dev. Psychobiol. 20, 7-18]. The results suggest that infant facial colour is not particularly important in mediating infant attractiveness to rhesus macaque females as previously suggested or that other infantile facial characteristics might be more important than colour in eliciting caretaking behaviours amongst females.

Behavioural and physiological aspects of stress and aggression in nonhuman primates

There is considerable interest in the study of stress and aggression in primates as a model for their interpretation in humans. Despite methodological and interpretational problems associated with behavioural and physiological measurement and definition, a considerable body of literature exists on these phenomena in primates. In the course of reviewing this literature we examine examples of many of the sources of variation in stress and aggression, including species identity, sex, age, breeding and social status, individual temperament, background, learning and resource distribution. This is followed by an examination of the interaction between stress and aggression before reviewing the most important areas in which changes in both stress and aggression are measured. In particular we examine those studies covering social aspects of an animal's life, specifically relating to social isolation, crowding as well as group formation, composition and instability. This review reveals the complex and often contradictory nature of relationships, not just between an animal's physiology and its behaviour, but between its stress status and display or receipt of aggression.

The development of mother-infant interactions after neonatal amygdala lesions in rhesus monkeys

As part of ongoing studies on the neurobiology of socioemotional behavior in the nonhuman primate, we examined the development of mother-infant interactions in 24 macaque monkeys who received either bilateral amygdala or hippocampus ibotenic acid lesions, or a sham surgical procedure at 2 weeks of age. After surgery, the infants were returned to their mothers and reared with daily access to small social groups. Behavioral observations of the infants in dyads (mother-infant pairs alone), tetrads (two mother-infant pairs), and social groups (six mother-infant pairs and one adult male) revealed species-typical mother-infant interactions for all lesion conditions, with the exception of increased physical contact time between the amygdala-lesioned infants and their mothers. Immediately after permanent separation from their mothers at 6 months of age, the infants were tested in a mother preference test that allowed the infants to choose between their mother and another familiar adult female. Unlike control and hippocampus-lesioned infants, the amygdala-lesioned infants did not preferentially seek proximity to their mother, nor did they produce distress vocalizations. Given the normal development of mother-infant interactions observed before weaning, we attribute the behavior of the amygdala-lesioned infants during the preference test to an impaired ability to perceive potential danger (i.e., separation from their mother in a novel environment), rather than to a disruption of the mother-infant relationship. These results are consistent with the view that the amygdala is not essential for fundamental aspects of social behavior but is necessary to evaluate potentially dangerous situations and to coordinate appropriate behavioral responses.

Recognition of line-drawing representations by a chimpanzee (Pan troglodytes)

The ability of a chimpanzee to recognize individuals portrayed in line drawings was evaluated. A 12-year-old female chimpanzee with extensive prior experience in the use of visual symbols matched the line drawings of chimpanzees, humans, and an orangutan with a specific letter of the alphabet. When a line drawing of a familiar individual was presented on the computer screen, the chimpanzee responded by punching a key with the letter of the alphabet that corresponded to the individual's name. Results indicate that the chimpanzee is able to categorize individuals from novel line-drawing representations.

Preferences of female rhesus monkeys (Macaca mulatta) for infantile coloration

While developmental researchers have long noted that infants of many mammalian species, including primates, have characteristic physical features, such as a distinctive coat or skin color, and some authors have further suggested that these features serve to elicit caretaking and solicitous behavior, few systematic investigations of the actual salience of such features for adult conspecifics have been carried out to date. The present series of 3 studies sought to determine whether natal coat and/or facial skin coloration might provide desirable visual stimulation for rhesus monkey adult females. In these studies the faces and/or fur of 6-month-old rhesus monkeys were dyed to simulate the normal coloration of rhesus monkey neonates. Adult females varying in parity and rearing history were then tested for their relative preference between these infantile-colored 6-month-olds and both normally colored 6-month-olds and other differentially colored control stimulus monkeys. Results indicated that regardless of parity or rearing history the adult female subjects exhibited consistent preferences for the stimulus animals with neonatal-like reddish-pink facial skin coloration.

Species discrimination in infant pigtail macaques with pictorial stimuli

Two experiments used a visual fixation habituation-dishabituation paradigm to study the ability of young, socially restricted pigtail macaques to discriminate among adults of 3 macaque species (pigtail, cynomolgus, and stumptail) with pictures as stimuli. The results of the 1st study demonstrated that 3-month-old pigtail infants could discriminate among faces of adult females of all 3 species. The 2nd study was methodologically similar to the 1st, which the exception that the face stimuli were presented upside-down. The results of Experiment II demonstrated no species discrimination, suggesting that the socially relevant discrimination demonstrated in Experiment I was a function of cues unique to the upright face and not a function of abstract cues available in both upright and upside-down facial stimuli.

Effect of surrogate-administered punishment on surrogate contact in infant squirrel monkeys

Three experiments were conducted in which surrogate-reared infant squirrel monkeys were exposed to punishment in the form of pressurized air emitted from the bodies of the surrogates. Punishment was administered irregularly during the day between the ages of 6 and 34 weeks, under different schedules of random presentation and at different parameters of the airblast stimulus. Physical contact with the surrogate was recorded separately for day and night activity. The results of all experiments were consistent in showing that punished infants spent less time than did nonpunished controls in contacting their surrogates during the daytime throughout the entire period of study. Nighttime scores were less consistent, but showed the same trend in 2 of the experiments. The results also suggested that different subtypes of squirrel monkeys are inherently different in their degree of surrogate contact, with monkeys of the Bolivian type spending more time in contact than those of either Peruvian or Colombian descent.