Performance in a tool-using task by common chimpanzees (Pan troglodytes), bonobos (Pan paniscus), an orangutan (Pongo pygmaeus), and capuchin monkeys (Cebus apella).

Performance by individual animals of three species of great apes (Pan troglodytes, Pan paniscus, and Pongo pygmaeus) and capuchin monkeys (Cebus apella) was assessed by presenting a food treat inside a clear tube. The subjects readily used a straight stick to obtain the food. When sticks were bundled together, the apes immediately unwrapped the bundle to obtain an individual stick, whereas capuchins attempted to insert the bundled sticks. When a misshapen stick was provided, apes, but not capuchins, showed an improvement in terms of modifying the misshapen stick before insertion. Our results indicate that all these species can solve these tasks. However, only the performance of apes is consistent with emerging comprehension of the causal relations required for the avoidance of errors in the more complex tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posture and reaching in chimpanzees (Pan troglodytes) and orangutans (Pongo pygmaeus).

Hand preference in reaching was assessed under 2 postural adjustment conditions in 40 chimpanzees (Pan troglodytes) and 6 orangutans (Pongo pygmaeus). The postural conditions were quadrupedal and upright, during which reaching for food was scored on a minimum of 50 trials. Results indicated no population preference during quadrupedal reaching, but a right-hand population preference was found during upright reaching. There were no significant effects of age or sex on either the direction or strength of hand preference. Early rearing history affected the strength of hand preference but not direction. The results suggest that posture is an important factor in the assessment of hand preference in great apes and may have important evolutionary consequences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative assessment of handedness for a coordinated bimanual task in chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla) and orangutans (Pongo pygmaeus).

Hand preferences for a coordinated bimanual task were assessed in a sample of 31 captive gorillas (Gorilla gorilla) and 19 captive orangutans (Pongo pygmaeus) and were compared with chimpanzee (Pan Troglodytes) hand preferences in subjects that were matched on the basis of age, sex, and rearing history. The task required that the apes remove food from the inside edges of a symmetrical polyvinyl chloride pipe presented to them in their home cages. The results indicate significant species differences with chimpanzees showing population-level right-handedness and orangutans showing population-level left-handedness. The gorillas showed a nonsignificant trend toward right-handedness. The results are discussed in terms of possible ecological or biomechanical factors that may influence hand preferences in different ape species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object permanence in orangutans (Pongo pygmaeus), chimpanzees (Pan troglodytes), and children (Homo sapiens).

Juvenile and adult orangutans (n?=?5; Pongo pygmaeus), chimpanzees (n?=?7; Pan troglodytes), and 19- and 26-month-old children (n?=?24; Homo sapiens) received visible and invisible displacements. Three containers were presented forming a straight line, and a small box was used to displace a reward under them. Subjects received 3 types of displacement: single (the box visited 1 container), double adjacent (the box visited 2 contiguous containers), and double nonadjacent (the box visited 2 noncontiguous containers). All species performed at comparable levels, solving all problems except the invisible nonadjacent displacements. Visible displacements were easier than invisible, and single were easier than double displacements. In a 2nd experiment, subjects saw the baiting of either 2 adjacent or 2 nonadjacent containers with no displacements. All species selected the empty container more often when the baited containers were nonadjacent than when they were adjacent. It is hypothesized that a response bias and inhibition problem were responsible for the poor performance in nonadjacent displacements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An obedient orangutan (Pongo abelii) performs perfectly in peripheral object-choice tasks but fails the standard centrally presented versions.

Mulcahy and Call (2009) found that bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) but not orangutans (Pongo pygmaeus) perform significantly better in a peripheral version of the object-choice task compared to the original central version. Orangutans may have failed because they avoided direct eye contact with the experimenter when the cue was given. We investigated this possibility by conducting peripheral and central object choice tasks with an obedient orangutan (Pongo abelii) whom the experimenter could elicit eye contact with in each trial. In contrast to Mulcahy and Call's findings, the subject only failed the object choice task when tested with the central and not the peripheral version. We investigated whether success was because of the greater distance the subject was required to move in order to make a choice in peripheral trials. Results show that this was an unlikely factor in the subject's success. We discuss our findings in relation to previous and future object-choice research. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Nonenculturated Orangutans' (Pongo pygmaeus) Use of Experimenter-Given Manual and Facial Cues in an Object-Choice Task.

Several experiments have been performed, to examine whether nonhuman primates are able to make use of experimenter-given manual and facial (visual) cues to direct their attention to a baited object. Contrary to the performance of prosimians and monkeys, great apes repeatedly have shown task efficiency in experiments such as these. However, many great ape subjects used have been "enculturated" individuals. In the present study, 3 nonenculturated orangutans (Pongo pygmaeus) were tested for their ability to use experimenter-given pointing, gazing, and glancing cues in an object-choice task. All subjects readily made use of the pointing gesture. However, when subjects were left with only gazing or glancing cues, their performance deteriorated markedly, and they were not able to complete the task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use of experimenter-given cues during object-choice tasks by chimpanzees (Pan troglodytes), an orangutan (Pongo pygmaeus), and human infants (Homo sapiens).

In a series of experiments, chimpanzees (Pan troglodytes), an orangutan (Pongo pygmaeus), and human infants (Homo sapiens) were investigated as to whether they used experimenter-given cues when responding to object-choice tasks. Five conditions were used in different phases: the experimenter tapping on the correct object, gazing plus pointing, gazing closely, gazing alone, and glancing without head orientation. The 3 subject species were able to use all of the experimenter-given cues, in contrast to previous reports of limited use of such cues by monkeys. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strategies used to combine seriated cups by chimpanzees (Pan troglodytes), bonobos (Pan paniscus), and capuchins (Cebus apella).

The authors investigated strategies used to combine seriated cups by apes (Pan troglodytes and P. paniscus) and monkeys (Cebus apella) using a protocol reported in P. M. Greenfield, K. Nelson, and E. Saltzman's (1972) study with children. It was hypothesized that apes would exhibit more hierarchical combinations of cups than monkeys, given apes' language capacity, and that apes would seriate the cups more efficiently than monkeys. As predicted, apes made many structures with the cups using a variety of strategies, and monkeys rarely combined the cups. After a training phase to orient monkeys to the task, the 2 genera did not differ in the strategies used to combine the cups or in efficiency in seriating the cups. Success in this task suggests that sensorimotor versions of hierarchically organized combinatorial activity are well within apes' and monkeys' abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Referential Understanding of Videos in Chimpanzees (Pan troglodytes), Orangutans (Pongo pygmaeus), and Children (Homo sapiens).

Performance on identical search tasks based on cues directly perceived or indirectly perceived through video were compared among a group of 4 adult chimpanzees (Pan troglodytes), a group of 2 adult orangutans (Pongo pygmaeus), and a group of 36 children (between 2 and 3 years of age). Children comprehended directly perceived cues but had difficulty with video cues. In contrast, chimpanzees and 1 orangutan were successful in using video to guide their search for a hidden object. Two follow-up studies with 3-year-old children demonstrated the importance of more distinct perceptual and verbal cues in aiding children's understanding of video as referring to real-world events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of response contingencies on scale model task performance by chimpanzees (Pan troglodytes).

The effects of modified procedures on chimpanzees' (Pan troglodytes) performance in a scale model comprehension task were examined. Seven chimpanzees that previously participated in a task in which they searched an enclosure for a hidden item after watching an experimenter hide a miniature item in the analogous location in a scale model were retested under procedures incorporating response costs. In Experiment 1, chimpanzees were trained under procedures that rewarded only item retrievals occurring on the 1st search attempt. During test trials, 6 chimpanzees performed above chance, including 4 that were previously unsuccessful under the original procedures (V. A. Kuhlmeier, S. T. Boysen, & K. L. Mukobi, 1999). Experiment 2 compared performance under the new and original procedures. Results indicated that for some chimpanzees, performance depended on procedures that decreased the use of competing search strategies and encouraged strategies based on information from the scale model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use of experimenter-given cues in visual co-orienting and in an object-choice task by a New World monkey species, Cotton Top Tamarins ( Saguinus oedipus ).

Two methods assessed the use of experimenter-given directional cues by a New World monkey species, cotton top tamarins (Saguinus oedipus). Experiment 1 used cues to elicit visual co-orienting toward distal objects. Experiment 2 used cues to generate responses in an object-choice task. Although there were strong positive correlations between monkey pairs to co-orient, visual co-orienting with a human experimenter occurred at a low frequency to distal objects. Human hand pointing cues generated more visual co-orienting than did eye gaze to distal objects. Significant accurate choices of baited cups occurred with human point and tap cues and human look cues. Results highlight the importance of head and body orientation to induce shared attention in cotton top tamarins, both in a task that involved food getting and a task that did not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How orangutans (Pongo pygmaeus) innovate for water.

We report an observational field study that aimed to identify innovative processes in rehabilitant orangutans’ (Pongo pygmaeus) water innovations on Kaja Island, Central Kalimantan, Indonesia. We tested for the basic model of innovating (make small changes to old behavior), 4 contributors (apply old behavior to new ends, accidents, independent working out, social cross-fertilization), development, and social rank. Focal observations of Kaja rehabilitants’ behavior over 20 months yielded 18 probable innovations from among 44 water variants. We identified variants by function and behavioral grain, innovations by prevalence, and innovative processes by relations between innovations, other behaviors, and social encounters. Findings indicate innovating by small changes and some involvement of all 4 contributors; midrank orangutans were the most innovative; and rehabilitants’ adolescent age profile, orphaning, and intense sociality probably enhanced innovativeness. Important complexities include: orangutan innovating may favor certain behavioral levels and narrowly defined similarities, and it may constitute a phase-like process involving a succession of changes and contributors. Discussion focuses on links with great ape cognition and parallels with innovating in humans and other nonhuman species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spontaneous classification in action by a human-enculturated and language-reared bonoboo (Pan paniscus) and common chimpanzees (Pan troglodytes).

The authors investigated the formal features of spontaneous manipulations used by 1 bonobo (Pan paniscus) and 2 common chimpanzees (Pan troglodytes) to classify objects in action. Chimpanzees' manipulations were evenly split between serial, one-at-a-time acts on 1 object and parallel, two-at-a-time acts on 2 or 3 objects. Chimpanzees systematically combined their manipulations into routines to generate class-consistent categories of objects. Their routines featured much reproduction of the same manipulations, planful acts that anticipated follow-up manipulations, and manipulations that were reciprocal to each other to accomplish an end. In all these respects, chimpanzees' manipulations were similar to those of 2-year-old human infants. In others they differed. Chimpanzees' routines were mainly based on a linear integration of manipulations. Classifying in action was only infrequently produced by hierarchically integrated routines. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Group differences in the mutual gaze of chimpanzees (Pan troglodytes).

A comparative developmental framework was used to determine whether mutual gaze is unique to humans and, if not, whether common mechanisms support the development of mutual gaze in chimpanzees and humans. Mother-infant chimpanzees engaged in approximately 17 instances of mutual gaze per hour. Mutual gaze occurred in positive, nonagonistic contexts. Mother-infant chimpanzees at a Japanese center exhibited significantly more mutual gaze than those at a center in the United States. Cradling and motor stimulation varied across groups. Time spent cradling infants was inversely related to mutual gaze. It is suggested that in primates, mutual engagement is supported via an interchangeability of tactile and visual modalities. The importance of mutual gaze is best understood within a perspective that embraces both cross-species and cross-cultural data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Language-naive chimpanzees (Pan troglodytes) judge relations between relations in a conceptual matching-to-sample task.

Three chimpanzees with a history of conditional and numeric token training spontaneously matched relations between relations under conditions of nondifferential reinforcement. Heretofore, this conceptual ability was demonstrated only in language-trained chimpanzees. The performance levels of the language-naive animals in this study, however, were equivalent to those of a 4th animal—Sarah—whose history included language training and analogical problem solving. There was no evidence that associative factors mediated successful performance in any of the animals. Prior claims of a profound disparity between language-trained and language-naive chimpanzees apparently can be attributed to prior experience with arbitrary tokens consistently associated with abstract relations and not language per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manual laterality in chimpanzees (Pan troglodytes) in complex tasks.

To determine the manual laterality of a sample of 24 chimpanzees, 4 problem apparatuses were used, the solution for which (obtaining a food item) required the use of 1 or both hands in sequential, simultaneous, or both sequential and simultaneous actions. The majority of the subjects showed significant and consistent hand preferences, especially in the actions that required a precision grip. The results obtained suggest the existence of factors linked to the specific characteristics of the task to be performed and to the ontogenetic maturation of the subject, which would influence the directionality and degree of the hand preference displayed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How cross-fostered chimpanzees ( Pan troglodytes ) initiate and maintain conversations.

This study systematically sampled typical attention-getting sounds and sign language conversations between each of 4 originally cross-fostered chimpanzees (Pan troglodytes), still living freely, but now in a laboratory setting, and a familiar human interlocutor. Videotape records showed that when they encountered a human interlocutor sitting alone at his desk with his back turned to them, the crossfosterlings either left the scene or made attention-getting sounds. The only signs they made to the interlocutor's back were noisy signs. When the human turned and faced them, the chimpanzees promptly signed to him (98% of the time) and rarely made any sounds during the ensuing signed conversations. Under systematic experimental conditions, the signed responses of the chimpanzees were appropriate to the conversational styles of the human interlocutor, confirming daily field observations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object permanence in orangutans (Pongo pygmaeus) and squirrel monkeys (Saimiri sciureus).

The authors tested orangutans (Pongo pygmaeus) and squirrel monkeys (Saimiri sciureus) on object permanence tasks. In Experiment 1, orangutans solved all visible displacements and most invisible displacements except those involving movements into 2 boxes successively. In Experiment 2, performance of orangutans on double invisible displacements and control displacements (assessing simple strategies) was compared. Orangutans did not use the simple strategy of selecting the box visited last by the experimenter. Instead, poorer performance on double invisible displacements may have been related to increased memory requirements. In Experiment 3, squirrel monkeys were tested using the procedure of Experiment 1. Squirrel monkeys solved visible but did not comprehend invisible displacements. Results suggest that orangutans but not squirrel monkeys possess Stage 6 object permanence capabilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Numerical judgments by chimpanzees (Pan troglodytes) in a token economy.

We presented four chimpanzees with a series of tasks that involved comparing two token sets or comparing a token set to a quantity of food. Selected tokens could be exchanged for food items on a one-to-one basis. Chimpanzees successfully selected the larger numerical set for comparisons of 1 to 5 items when both sets were visible and when sets were presented through one-by-one addition of tokens into two opaque containers. Two of four chimpanzees used the number of tokens and food items to guide responding in all conditions, rather than relying on token color, size, total amount, or duration of set presentation. These results demonstrate that judgments of simultaneous and sequential sets of stimuli are made by some chimpanzees on the basis of the numerousness of sets rather than other non-numerical dimensions. The tokens were treated as equivalent to food items on the basis of their numerousness, and the chimpanzees maximized reward by choosing the larger number of items in all situations. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Hand preferences for a coordinated bimanual task in 110 chimpanzees (Pan troglodytes): Cross-sectional analysis.

Hand preference for a coordinated bimanual task was assessed in a sample of 110 chimpanzees (Pan troglodytes). Subjects were presented with opaque tubes, the inside of which was coated with peanut butter. The hand and finger used to extract the peanut butter was recorded in 2 test sessions. A population right-hand bias was found. Juvenile and adolescent subjects were less lateralized than adults. All subjects primarily used their index finger to extract peanut butter. Use of the index finger was higher in adults and adolescents compared with juveniles. The results suggest that coordinated bimanual tasks (a) elicit strong hand preferences at the individual level and (b) elicit population level right-handedness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)