Object manipulation in a captive troop of Japanese monkeys (Macaca fuscata): A developmental analysis

A captive troop of Japanese monkeys (Macaca fuscata) was presented with a nylon rope, a wooden cube, and an iron tube, and their subsequent manipulations were observed in detail. In total, 202 manipulation patterns were distinguished on the basis of three components: the actions performed, body-parts used, and relations to other objects. The developmental changes in these modes of manipulation were analyzed cross-sectionally, revealing four characteristics: (1) the most manipulative members of the troop were those aged 2–3 and 4–6 years old; (2) most of the manipulatory repertoire appeared by 4–6 years old; (3) actions such as Roll, Rub, and Slide and the use of bodyparts continued to increase in variety until 4–6 years old, while the variety of other actions showed plateaus after 2–3 years old or an earlier age; and (4) secondary manipulations appeared at 1 year old and continued to increase in variety even after 4–6 years old.     

A comparative study of the variety and complexity of object manipulation in captive chimpanzees (Pan troglodytes) and bonobos (Pan paniscus)

Four types of specific objects: wooden spoons, metal bowls, plastic boxes, and cotton towels were introduced in a similar setting to two captive groups of different species in the genusPan, the bonobo and the chimpanzee. In total, 582 unique manipulation forms were distinguished by a set of variables: types of objects, motor patterns, body-parts used, the number of objects manipulated, and types of orienting manipulation. In sum, chimpanzees and bonobos were not so different in the variety and the complexity of object manipulation forms. However, comparison of the two species revealed significant differences as follows: (1) chimpanzees preferred to use only one hand during manipulation of both single- and multiple-objects, whereas in the case of multiple-objects bonobos used both hands significantly more often; (2) chimpanzees performed more orienting manipulations in single-object manipulations than did bonobos, whereas the reverse was the case in multiple-object manipulations; and (3) chimpanzees' object manipulations were overall more substrate-oriented than were bonobos'. The factors producing these differences are discussed in relation to positional behaviors and habitual tool use in the two species.     

Old,socially housed rhesus monkeys manipulate objects

Recent research has indicated that old, individually housed monkeys show little interest in novel objects. Yet unanswered is whether this effect is caused primarily by age or housing condition. The purpose of this study was to assess the role of social living in promoting responsiveness to objects. We measured the rates of object manipulation in older animals, assessed responsiveness over time to particular objects as a measure of habituation, and examined social influences on object use. Several social groups of rhesus monkeys that contained older adults were studied. These groups were housed in indoor pens or in an outdoor enclosure, and all monkeys had continuous access to a variety of objects in their home environment. In contrast to previous studies of individually housed monkeys, our group-housed monkeys showed sustained interest in objects. Old monkeys manipulated objects extensively, and this response was all the more significant, given that the objects were not novel. Monkeys housed in an outdoor enclosure showed object manipulation patterns that were not different from monkeys housed in indoor pens. However, females exhibited much higher object-related responses than males. Social facilitation played a role in the reactions of some monkeys to objects. Patterns of social facilitation as well as avoidance were present in two of the three indoor groups that were observed. Failure to manipulate objects in rhesus macaques appears to be more a function of individual housing than of old age. Factors such as environmental complexity, social needs, and early experience should be considered in order to understand why individually housed rhesus monkeys are unresponsive to objects. © 1993 Wiley-Liss, Inc.     

Quantitative analysis of small group interaction in rhesus monkeys

The effect of role relations on social interaction in small groups of rhesus monkeys was examined quantitatively, through use of an interval scale of social behavior. Concurrent pair interactions were tabulated for all possible combinations in 24 triad groups: Six groups containing three males; six groups containing three females; six groups of one male, two females; and six groups of two males and one female. A specific behavior which involves participation of all three animals at once, the incitement interaction, was found to quantitatively alter each monkey's reaction to other social behaviors displayed at the same time. The interaction demonstrates the monkeys' attention to and manipulation of role relations. In all triad types one could quantitatively document the fact that the most subordinate monkey established a role with the most dominant monkey which allowed it some freedom to behave less submissively when interacting with the middle ranking monkey. This general phenomenon in role relations may contribute to group cohesiveness.     

Sensorimotor cognition in young feral orangutans (Pongo pygmaeus)

The goal of this study was to describe object manipulation in wild orangutan infants and juveniles. Object manipulation is an important subsistence activity that also reflects cognitive functioning. Orangutans were studied in the field, at the Tanjung Puting Reserve, Kalimantan Tengah, Indonesia. Fourteen orangutans, grouped by age (infants 2.5 to 4.6 years; juveniles 5 to 8.5 years), were observed over a total of 555 hr and for an average of three full dawn-to-dusk “follows” each. Young orangutan’s manipulations were categorized along a hierarchy of complexity. The least complex manipulations were single sensorimotor actions such as grasping, mouthing, and waving. The most complex manipulations were combinations and coordinations of actions, such as experimentation with objects, tool use, and planning. Manipulative behavior occurred mainly when foraging, i.e. when obtaining and processing food items. Interestingly, complex behavior occurred most often when locomoting. The most complex object manipulations, however, occurred rarely. Infants and juveniles exhibited equivalent levels of complexity. Several aspects of this study point to the importance of social assistance provided by competent mothers for the development of young orangutans’ ability to locomote and to locate, obtain, and process food items. This study also highlights the cognitive abilities of young wild orangutans regarding tool use.     

Further report on object manipulation in non-human primates: A comparison within 13 species of the genusMacaca

Thirteen captive species of the genusMacaca were presented with certain non-edible objects and the subsequent manipulation was observed. The following results were obtained: (1) Thefascicularis group species displayed a great variety in rolling the manipulandum, which has been reported to be one of the actions characterizing cercopithecine species; (2) manipulating the object with one finger was typical of thesilenus-sylvanus andsinica groups, whereas use of the fingers moving opposably was common to all species ofMacaca; (3) secondary manipulations in relation to the wire-mesh were observed only inM. silenus, M. sinica, andM. nemestrina, whereas those in relation to water were common to allMacaca species; and (4) within-subgroup differences were great in thesilenus-sylvanus andsinica groups as compared to thefascicularis group.     

When and how well can human‐socialized capuchins match actions demonstrated by a familiar human?

Capuchin monkeys have provided uneven evidence of matching actions they observe others perform. In accord with theories emphasizing the attentional salience of object movement and spatial relationships, we predicted that human-reared monkeys would better match events in which a human demonstrator moved an object into a new relation with another object or surface than other kinds of actions. Three human-reared capuchins were invited repeatedly by a familiar human to perform a fixed set of actions upon objects or upon their bodies, using the "Do as I do" procedure. Actions directed at the body were matched less reliably than actions involving objects, and actions were matched best when the monkey looked at the demonstration for at least 2 sec and performed its action within a few seconds after the demonstration. The most commonly matched actions were those that one monkey performed relatively often when the experiment began. One monkey partially reproduced three novel actions (out of 48 demonstrations), all three involving moving or placing objects, and two of which it also performed following other demonstrations. These findings contribute convergent evidence that capuchin monkeys display social facilitation of activity, enhanced interest in particular objects and emulation of spatial outcomes. This pattern can support the development of shared manipulative skills, as evident in traditions of foraging and tool use in natural settings. The findings do not suggest that human rearing substantively altered capuchins' ability or interest in matching the actions of a familiar human, although visual attention to the human demonstrator may have been greater in these monkeys than in normally reared monkeys.     

Spatial selectivity to manipulate portable objects in wedge-capped capuchins (Cebus olivaceus)

We studied the manipulative activity of five wedge-capped capuchins (Cebus olivaceus) confronted with different types of unfamiliar and portable objects: wooden blocks, plastic rings, spoons, and coconuts. Combinatorial manipulations involving two portable objects of the same type were quite frequent. The lately introduced objects, whatever their kind, appeared as the most attractive. Nevertheless, some objects remained very attractive throughout the overall experiment, especially the wooden blocks which elicited more combinatorial and striking behaviors than the other objects. Concerning space, we observed that the individuals choose specific locations to perform their manipulative acts. The spatial distributions of these acts were more concentrated, and less concordant between individuals, in the present study than in two others conducted with the same group but involving the manipulation of familiar objects. This suggests that individual differences were more marked when the subjects manipulated unfamiliar objects than when they manipulated familiar ones. This finding may have applications when the members of a group have to benefit from an enrichment of their environment.     

The antecedents of man the manipulator

Four individuals of each of ten Primates species were presented with a length of nylon rope and their manipulative responses recorded in detail. The 172 specific types of actions observed were consolidated into 69 generic categories and then further taxonomized into Primary actions, in which the rope was directly acted upon, of two types depending on whether the rope was grasped or not, and Secondary actions, in which the rope was manipulated with respect to objects, with two types depending upon whether the second object was a part of the body or part of the environment.The ten species tended to fall into two groups: (1) the lemurs, highly arboreal monkeys, and gibbons, and (2) a less arboreal monkey and the great apes. The latter group generally engaged in more different types of actions, more secondary actions, more intentional contacts, more action away from the body, more proximal body contact, and more species-unique actions.It was inferred from these and other data that the antecedents of Man were more object-interested and manipulative than the precursors of nonhuman Primates at comparable levels of brain size development.     

Forelimb dimensions and goniometry of the wrist and fingers in tufted capuchin monkeys (Cebus apella): Developmental and comparative aspects

Adult capuchin monkeys use precision grips during manipulation of small objects, although their thumbs have been classified as pseudo-opposable. We investigated the physical properties of the hands to increase our understanding of manual function in capuchins. Forelimb dimensions and joint mobility (goniometric) measurements were obtained from adult, juvenile, and infant tufted capuchins (Cebus apella). Compared to adult squirrel monkeys, adult capuchins exhibited less flexibility of the wrist and digits. Capuchins of all ages had proportionally longer hands than squirrel monkeys, and capuchins more than 7 weeks old had proportionally longer thumbs than squirrel monkeys. Growth of the arms and hands was asynchronous. The duration of growth of the thumb was particularly prolonged, extending into early adulthood. Age-related changes in flexibility were apparent in most indices, and were greatest at the metacarpophalangeal joints. It is unknown to what extent the characteristics of growth, forelimb dimensions, and goniometry presented by capuchins are shared with other species, or if they contribute to the capuchin's unusual prehensive capacities. However, the marked differences between adult capuchins and squirrel monkeys in these metrics, and between capuchins and rhesus in the growth patterns of the digits, suggest that variation across taxa in these characteristics can be considerable.     

Effects of manipulatable objects on the activity of captive capuchin monkeys (Cebus apella)

The aim of this study was to evaluate simple behavioral enrichment procedures for a captive group of tufted capuchin monkeys (Cebus apella). We examined the effects of providing a manipulatable substrate (straw) and a variety of portable objects in the monkeys' home cage. The animals were observed across three conditions in two replications: 1) No portable objects were present; 2) a set of six identical portable objects was present; and 3) a set of six varied portable objects was present. The cage floor was bare in the first replication; straw was uniformly spread on the cage floor in the second replication. An 18-month period of qualitative note taking followed completion of the initial data collection phase. The presence of straw and portable objects affected patterns of affiliation by decreasing quiet contact and close proximity. Providing additional manipulative opportunities affected both the form and frequency of object-directed activities. Object contacts were directed toward a greater variety of targets, and some objects were spontaneously used as tools. Manipulation of provided objects and use of objects as tools have become routine activities in this group of monkeys. We conclude that providing straw and portable objects in an already well equipped cage is an effective means of long-term behavioral enrichment for captive capuchin monkeys. Enabling captive capuchins to express species-typical manipulative tendencies is apparently conducive to the monkeys' optimal physical and psychological well-being as well as interesting to the human observer.     

Generalization of Dexterous Manipulation Is Sensitive to the Frame of Reference in Which It Is Learned

Studies have shown that internal representations of manipulations of objects with asymmetric mass distributions that are generated within a specific orientation are not generalizable to novel orientations, i.e., subjects fail to prevent object roll on their first grasp-lift attempt of the object following 180° object rotation. This suggests that representations of these manipulations are specific to the reference frame in which they are formed. However, it is unknown whether that reference frame is specific to the hand, the body, or both, because rotating the object 180° modifies the relation between object and body as well as object and hand. An alternative, untested explanation for the above failure to generalize learned manipulations is that any rotation will disrupt grasp performance, regardless if the reference frame in which the manipulation was learned is maintained or modified. We examined the effect of rotations that (1) maintain and (2) modify relations between object and body, and object and hand, on the generalizability of learned two-digit manipulation of an object with an asymmetric mass distribution. Following rotations that maintained the relation between object and body and object and hand (e.g., rotating the object and subject 180°), subjects continued to use appropriate digit placement and load force distributions, thus generating sufficient compensatory moments to minimize object roll. In contrast, following rotations that modified the relation between (1) object and hand (e.g. rotating the hand around to the opposite object side), (2) object and body (e.g. rotating subject and hand 180°), or (3) both (e.g. rotating the subject 180°), subjects used the same, yet inappropriate digit placement and load force distribution, as those used prior to the rotation. Consequently, the compensatory moments were insufficient to prevent large object rolls. These findings suggest that representations of learned manipulation of objects with asymmetric mass distributions are specific to the body- and hand-reference frames in which they were learned.     

A test of the generalizability of the interval scale developed for social behavior of rhesus monkeys

An interval scale of behavior would be useful in the study of social relations because it would allow the whole behavioral repertory to be used simultaneously and would allow greater flexibility in statistical manipulation. Maxim has developed such a scale using isolated dyads of unfamiliar monkeys. The typical social environment of monkeys, however, consists of familiar monkeys in mixed age and sex groups. This study replicates Maxim's procedure and tests the applicability of a scale developed with isolated dyads to groups of familiar monkeys. The scale developed here differed substantially from Maxim's. Behavior of monkeys in these groups was much more variable than behavior of monkeys in Maxim's isolated dyads. Behaviors at the extremes of the scale were similarly arranged in both scales, but behaviors in the central region were more labile and disordered. Distances between behaviors at the extreme of this scale were significantly larger than those in the central region whereas there were no differences in Maxim's scale. While some of these differences may be accounted for by group size and familiarity, several difficulties remain. Some behaviors may change meaning across different contexts and social relationships. The generalizability of these scales, therefore, may be limited to the behavior of groups of similar composition and familiarity.     

Assessing the home environment during mid- and late-adolescence

The late adolescence version of the HOME Inventory (LA-HOME) documents actions, objects, events, and conditions connected with the home environment of children ages 16 and older still living at home. The study entailed a multi-stage process of measurement construction and validation that involved over 400 families from four states. The families were diverse by family composition, race/ethnicity, and socioeconomic status. Findings indicated expected relations between scores on six constituent domains of LA-HOME and measures of both family context and adolescent development. Relations varied across race/ethnic groups but were similar to those observed for the other four age-based versions of the HOME Inventory.     

Macaques (Macaca nemestrina) recognize when they are being imitated

This study investigated whether monkeys recognize when a human experimenter imitates their actions towards an object. Two experimenters faced 10 pigtailed macaques, who were given access to an interesting object. One experimenter imitated the monkeys' object-directed actions, the other performed temporally contingent but structurally different object-directed actions. Results show a significant visual preference for the imitator during manual object manipulations, but not mouthing actions. We argue that the ability to match actions could be based on both visual-visual and kinaesthetic-visual matching skills, and that mirror neurons, which have both visual and motor properties, could serve as a neural basis for recognizing imitation. However, imitation recognition as assessed by visual preference does not necessarily imply the capacity to attribute imitative intentionality to the imitator. The monkeys might implicitly recognize when they are being imitated without deeper insight into the mental processes of others.     

The study of tool use as the way for general estimation of cognitive abilities in animals

Investigation of tool use is an effective way to determine cognitive abilities of animals. This approach raises hypotheses, which delineate limits of animal's competence in understanding of objects properties and interrelations and the influence of individual and social experience on their behaviour. On the basis of brief review of different models of manipulation with objects and tools manufacturing (detaching, subtracting and reshaping) by various animals (from elephants to ants) in natural conditions the experimental data concerning tool usage was considered. Tool behaviour of anumals could be observed rarely and its distribution among different taxons is rather odd. Recent studies have revealed that some species (for instance, bonobos and tamarins) which didn't manipulate tools in wild life appears to be an advanced tool users and even manufacturers in laboratory. Experimental studies of animals tool use include investigation of their ability to use objects physical properties, to categorize objects involved in tool activity by its functional properties, to take forces affecting objects into account, as well as their capacity of planning their actions. The crucial question is whether animals can abstract general principles of relations between objects regardless of the exact circumstances, or they develop specific associations between concerete things and situations. Effectiveness of laboratory methods is estimated in the review basing on comparative studies of tool behaviour, such as "support problem", "stick problem", "tube- and tube-trap problem", and "reserve tube problem". Levels of social learning, the role of imprinting, and species-specific predisposition to formation of specific domains are discussed. Experimental investigation of tool use allows estimation of the individuals' intelligence in populations. A hypothesis suggesting that strong predisposition to formation of specific associations can serve as a driving force and at the same time as obstacle to animals' activity is discussed. In several "technically gifted" species (such as woodpecker finches, New Caledonian crows, and chimpanzees) tool use seems to be guided by a rapid process of trial and error learning. Individuals that are predisposed to learn specific connections do this too quickly and thus become enslaved by stereotypic solutions of raising problems.     

Individual and sex differences in learning abilities of ravens

Behavioral and physiological characteristics of individuals within the same species have been found to be stable across time and contexts. In this study, we investigated individual differences in learning abilities and object and social manipulation to test for consistency within individuals across different tasks. Individual ravens (Corvus corax) were tested in simple color and position discrimination tasks to establish their learning abilities. We found that males were significantly better in the acquisition of the first discrimination task and the object manipulation task, but not in any of the other tasks. Furthermore, faster learners engaged less often in manipulations of conspecifics and exploration of objects to get access to food. No relationship between object and social manipulation and reversal training were found. Our results suggest that individual differences in regard to the acquisition of new tasks may be related to personalities or at least object manipulation in ravens.     

Relationships in six groups of rhesus monkeys II. Dyads

Dyadic relationships are described for rhesus monkeys living in six groups. The kinds, frequencies, directionality, and overall patterning of interactions are examined over a twelve-month period for adult males, adult females, and young monkeys. Kinship, sex, age, reproductive conditions, time, events, and other social relations all affected dyadic relationship. Certain patterns of interactions characterized different relationships, such as those termed “special,” “tense,” “affiliative,” “conflicting.” A component approach is recommended for the understanding of relationships based on an appraisal of attraction, familiarity, and deference between individuals. The importance of assessing relationships in the group context is stressed.     

How bearded capuchin monkeys (Sapajus libidinosus) prepare to use a stone to crack nuts

Bearded capuchin monkeys crack nuts with naturally varying stone hammers, suggesting they may tune their grips and muscular forces to each stone. If so, they might use discrete actions on a stone before lifting and striking, and they would likely use these actions more frequently when the stone is larger and/or less familiar and/or when first initiating striking. We examined the behavior of (a) four monkeys (all proficient at cracking nuts) with two larger (1 kg) and two smaller (0.5 kg) stones, (b) 12 monkeys with one 1 kg stone, and (c) one monkey during its first 100 strikes with an initially unfamiliar 1 kg stone. Bearded capuchin monkeys used three discrete actions on the stone before striking, all more often with the larger stones than the smaller stones. We infer that the first discrete action (Spin) aided the monkey in determining where to grip the stone, the second (Flip) allowed it to position the stone on the anvil ergonomically before lifting it, and the third (Preparatory Lift) readied the monkey for the strenuous lifting action. The monkey that provided 100 strikes with one initially unfamiliar stone performed fewer Spins in later strikes but performed Flip and Preparatory Lift at consistent rates. The monkeys gripped the stone with both hands along the sides to lift it, but usually moved one or both hands to the top of the stone at the zenith of the lift for the downward strike. The findings highlight two new aspects of the capuchins’ nut‐cracking: (a) Anticipatory actions with the stone before striking, especially when the stone is larger or unfamiliar, and when initiating striking and (b) shifting grips on the stone during a strike. We invite researchers to investigate if other taxa use anticipatory actions and shift their grips during percussive activity.