Human and chimpanzee face recognition in chimpanzees (Pan troglodytes): Role of exposure and impact on categorical perception.

The respective influences of exposure and inborn neural networks on conspecific and nonconspecific face processing remain unclear. Although the importance of exposure in the development of object and face recognition in general is well documented, studies explicitly comparing face recognition across species showed a species-specific effect. For instance, laboratory monkeys exposed daily to human faces were better at discriminating monkeys than humans, suggesting that the role of exposure may not be the only factor affecting cross-species recognition. In the present study, the authors investigated conspecific and nonconspecific face recognition in chimpanzees (Pan troglodytes) from 2 primate centers that provided different exposure to chimpanzee and human faces. The authors showed that the chimpanzees from the center providing more exposure to human faces than to chimpanzee faces were better at discriminating human faces than they were at discriminating chimpanzee faces. The chimpanzees from the other center did not show the same effect. A computational simulation was developed to evaluate the average similarities among human pictures and among chimpanzee pictures. Both categories were comparable. Chimpanzees' scores were significantly correlated with the similarity coefficients. Overall, the results show that exposure is a critical determinant in conspecific and nonconspecific face recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhesus monkeys (Macaca mulatta) lack expertise in face processing.

Faces are salient stimuli for primates that rely predominantly on visual cues for recognizing conspecifics and maintaining social relationships. While previous studies have shown similar face discrimination processes in chimpanzees and humans, data from monkeys are unclear. Therefore, three studies examined face processing in rhesus monkeys using the face inversion effect, a fractured face task, and an individual recognition task. Unlike chimpanzees and humans, the monkeys showed a general face inversion effect reflected by significantly better performance on upright compared to inverted faces (conspecifics, human and chimpanzees faces) regardless of the subjects' expertise with those categories. Fracturing faces alters first- and second-order configural manipulations whereas previous studies in chimpanzees showed selective deficits for second-order configural manipulations. Finally, when required to individuate conspecific's faces, i.e., matching two different photographs of the same conspecific, monkeys showed poor discrimination and repeated training. These results support evolutionary differences between rhesus monkeys and Hominoids in the importance of configural cues and their ability to individuate conspecifics' faces, suggesting a lack of face expertise in rhesus monkeys. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use of multiple-alternative matching-to-sample in the study of visual search in a chimpanzee (Pan troglodytes).

Visual search in a chimpanzee and in humans were compared under the multiple-alternative matching-to-sample (MTS) procedure, in which a sample stimulus was followed by 1 positive (target) and several negative comparison stimuli (distractors). Reaction times (RTs) in the chimpanzee were affected by the number of distractors, the target–distractor similarity, and the uniformity of search display. Similar results were also obtained from humans and suggest that the performance by the chimpanzee may involve the same visual information-processing capabilities as those required in the human visual search performance. The multiple-alternative MTS is useful for studying various visual perceptual–cognitive abilities of animals including chimpanzees. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recognizing facial cues: Individual discrimination by chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta).

Faces are one of the most salient classes of stimuli involved in social communication. Three experiments compared face-recognition abilities in chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). In the face-matching task, the chimpanzees matched identical photographs of conspecifics' faces on Trial 1, and the rhesus monkeys did the same after 4 generalization trials. In the individual-recognition task, the chimpanzees matched 2 different photographs of the same individual after 2 trials, and the rhesus monkeys generalized in fewer than 6 trials. The feature-masking task showed that the eyes were the most important cue for individual recognition. Thus, chimpanzees and rhesus monkeys are able to use facial cues to discriminate unfamiliar conspecifics. Although the rhesus monkeys required many trials to learn the tasks, this is not evidence that faces are not as important social stimuli for them as for the chimpanzees. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early sensorimotor development in chimpanzees (Pan troglodytes).

Examined the cognitive and locomotor development of 4 chimpanzees (Pan troglodytes) during their 1st yr of life with Piagetian theory and method as paradigm. The infant chimpanzees progressed through the same 4 stages of development as babies do. However, the chimpanzees seemed less developed than babies in object exploration and in object–object combination. When chimpanzee early cognition is compared with that of other nonhuman primates, chimpanzees appear more advanced than gorillas, capuchins, and macaques in these same areas of cognition and similar to orangutans. A unitary explanation of the relative advances and delays in chimpanzee early cognition, which refers to the relation between rates of locomotor and cognitive development, is proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reduction of Th1 cell activity in the peripheral circulation of patients with rheumatoid arthritis after treatment with a non-depleting humanized monoclonal antibody to CD4

Differences in early events during entry and integration of HIV-1 into peripheral blood mononuclear cells (PBMC) might contribute to the absence of AIDS-like disease in chimpanzees as compared to humans. To address this question, we first tested the in vitro susceptibility of human and chimpanzee PBMC for infection with the two HIV-1 isolates III B and RF. The results of these studies revealed that chimpanzee PBMC had a slightly lower capability to support the growth of HIV-1 as compared to human PBMC. This was accompanied by a delayed accumulation of proviral HIV-1 DNA in cultures of HIV-1-infected chimpanzee PBMC. However, no differences between cells of the two species were observed when very early events of HIV-1 infection were studied. Shortly (20 h) after infection chimpanzee and human cells harbored similar amounts of proviral HIV-1 DNA and PBMC of both species behaved comparably with respect to pre-integration latency (i.e. the ability to activate extrachromosomal HIV-1 intermediates in HIV-1 infected quiescent cells at various times after infection). These results strongly suggest that the absence of AIDS-like disease in chimpanzees cannot be correlated with defects in early events of the HIV-1 replicative cycle.     

Recognition bias for safe faces in panic disorder with agoraphobia

Panic patients with agoraphobia were compared with normal controls on tasks of face recognition. The subjects were presented with 20 photos, and were required to make a judgement of the persons on the photos; shortly afterwards they were unexpectedly presented with a recognition task. In the first study, one task was to judge whether the persons on the photos were critical or accepting: unlike social phobics (Lundh and Ost, 1996b, Behaviour Research and Therapy, 34, 787-794), panic patients showed no bias for critical vs accepting faces on the recognition task. In a secondary study, the task was to judge whether the persons on the photos were 'safe' or 'unsafe', i.e. whether they could be relied on if the subject would need help in some situation. The results showed a recognition bias for safe vs neutral faces in panic patients. The index of recognition bias for safe faces correlated with avoidance of feared situations when accompanied by others, as measured by the Mobility Inventory. The possibility that memory bias in emotional disorders is a function of basic concern, or functional importance, rather than positive/negative valence is discussed. The results are also discussed in terms of degree of elaboration, exposure duration of the stimuli, and the generality of the findings.     

Experimental infection of chimpanzees with hepatitis C virus of genotype 5a: genetic analysis of the virus and generation of a standardized challenge pool

Six major genotypes (genotypes 1-6) of hepatitis C virus (HCV) have been identified. These genetic variants are being transmitted to chimpanzees, the only recognized animal model for the study of HCV. Genotype 5a (strain SA13), a variant found primarily in South Africa, has been transmitted to chimpanzees for the first time. Experimental infection of 2 chimpanzees was characterized by early appearance of viremia and peak virus titers of 10(5)-10(6) genome equivalents/mL. The HCV infection was resolved by week 15 after inoculation in 1 chimpanzee and persisted in the other. Both chimpanzees became anti-HCV-positive by week 14 after inoculation. Both chimpanzees developed viral hepatitis. The infectivity titer of a genotype 5a challenge pool prepared from the first passage of HCV in a chimpanzee was approximately 10(4) infectious doses/mL. Finally, sequence analysis of strain SA13 confirmed that genotype 5a is genetically distinct from other genotypes of HCV.     

Visual kin recognition in nonhuman primates: (Pan troglodytes and Macaca mulatta): Inbreeding avoidance or male distinctiveness?

Faces provide important information about identity, age, and even kinship. A previous study in chimpanzees reported greater similarity between the faces of mothers and sons compared with mothers and daughters, or unrelated individuals. This was interpreted as an inbreeding avoidance mechanism where females, the dispersing gender, should avoid mating with any male that resembles their mother. Alternatively, male faces may be more distinctive than female faces, biasing attention toward males. To test these hypotheses, chimpanzees and rhesus monkeys matched conspecifics' faces of unfamiliar mothers and fathers with their sons and daughters. Results showed no evidence of male distinctiveness, rather a cross-gender effect was found: chimpanzees were better matching moms with sons and fathers with daughters. Rhesus monkeys, however, showed an overwhelming bias toward male-distinctiveness. They were faster to learn male faces, performed better on father–offspring and parent–son trials, and were best matching fathers with sons. This suggests that for the rhesus monkey, inbreeding avoidance involves something other than facial phenotypic matching but that among chimpanzees, the visual recognition of facial similarities may play an important role. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of AIDS in a chimpanzee infected with human immunodeficiency virus type 1

The condition of a chimpanzee (C499) infected with three different isolates of human immunodeficiency virus type 1 (HIV-1) for over 10 years progressed to AIDS. Disease development in this animal was characterized by (i) a decline in CD4+ cells over the last 3 years; (ii) an increase in viral loads in plasma; (iii) the presence of a virus, termed HIV-1JC, which is cytopathic for chimpanzee peripheral blood mononuclear cells; and (iv) the presence of an opportunistic infection and blood dyscrasias. Genetic analysis of the V1-V2 region of the envelope gene of HIV-1JC showed that the virus present in C499 was significantly divergent from all inoculating viruses (> or = 16% divergent at the amino acid level) and was suggestive of a large quasispecies. Blood from C499 transfused into an uninfected chimpanzee (C455) induced a rapid and sustained CD4+-cell decline in the latter animal, concomitant with high plasma viral loads. These results show that HIV-1 can induce AIDS in chimpanzees and suggest that long-term passage of HIV-1 in chimpanzees can result in the development of a more pathogenic virus.     

Classifying chimpanzee facial expressions using muscle action.

The Chimpanzee Facial Action Coding System (ChimpFACS) is an objective, standardized observational tool for measuring facial movement in chimpanzees based on the well-known human Facial Action Coding System (FACS; P. Ekman & W. V. Friesen, 1978). This tool enables direct structural comparisons of facial expressions between humans and chimpanzees in terms of their common underlying musculature. Here the authors provide data on the first application of the ChimpFACS to validate existing categories of chimpanzee facial expressions using discriminant functions analyses. The ChimpFACS validated most existing expression categories (6 of 9) and, where the predicted group memberships were poor, the authors discuss potential problems with ChimpFACS and/or existing categorizations. The authors also report the prototypical movement configurations associated with these 6 expression categories. For all expressions, unique combinations of muscle movements were identified, and these are illustrated as peak intensity prototypical expression configurations. Finally, the authors suggest a potential homology between these prototypical chimpanzee expressions and human expressions based on structural similarities. These results contribute to our understanding of the evolution of emotional communication by suggesting several structural homologies between the facial expressions of chimpanzees and humans and facilitating future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recent use of signs by chimpanzees (Pan troglodytes) in interactions with humans.

In light of the controversy about the linguistic properties of chimpanzee signing behavior, the recent sign use of 5 chimpanzees (Pan troglodytes) with long histories of sign use was analyzed while they interacted with longtime human companions. Four corpora from 1992 to 1999 consisting of 3,448 sign utterances were examined. The chimpanzees predominantly used object and action signs. There was no evidence for semantic or syntactic structure in combinations of signs. Longer combinations showed repetition and stringing of object and action signs. The chimpanzees mostly signed with an acquisitive motivation. Requests for objects and actions were the predominant communicative intentions of the sign utterances, though naming and answering also occurred. This recent sign use shows multiple differences with (early) human language. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chimpanzees (Pan troglodytes) remember the location of a hidden food item after altering their orientation to a spatial array.

Two chimpanzees (Pan troglodytes) had a direct view of an experimenter placing a food item beneath one of several cups within a horizontal spatial array. The chimpanzees then were required to move around the spatial array, shifting their orientation to the array by 180°. Both chimpanzees remembered the location of the food item. In the next experiment, a visual barrier was placed between the chimpanzees and the spatial array after the food item had been hidden to prevent visual tracking of the location of the object during the chimpanzees' movement. One chimpanzee remembered the location of the hidden item in this variation. These results demonstrate another capacity for spatial memory in this species that complements data indicating chimpanzee spatial memory for invisible displacements, array rotations, and array transpositions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chimpanzees (Pan troglodytes) conceal visual and auditory information from others.

Chimpanzees (Pan troglodytes) competed with a human for food. The human sat inside a booth, with 1 piece of food to her left and 1 to her right, which she could retract from her chimpanzee competitor's reach as needed. In Experiment 1, chimpanzees could approach either side of the booth unseen but then had to reach through 1 of 2 tunnels (1 clear, 1 opaque) for the food. In Experiment 2, both tunnels were clear and the human was looking away, but 1 of the tunnels made a loud noise when it was opened. Chimpanzees preferentially reached through the opaque tunnel in the first study and the silent tunnel in the second, successfully concealing their taking of the food from the human competitor in both cases. These results suggest that chimpanzees can, in some circumstances, actively manipulate the visual and auditory perception of others by concealing information from them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Matching faces to photographs: Poor performance in eyewitness memory (without the memory).

Eyewitness memory is known to be fallible. We describe 3 experiments that aim to establish baseline performance for recognition of unfamiliar faces. In Experiment 1, viewers were shown live actors or photos (targets), and then immediately presented with arrays of 10 faces (test items). Asked whether the target was present among the test items, and if so to identify the person, participants showed poor performance levels (roughly 70% accurate). Furthermore, there was no difference between immediate memory for a live person and photograph. In Experiment 2, the same targets and test items were presented simultaneously, and participants were asked to perform a matching task. Again, performance was poor (roughly 68% accurate), with no difference between matching photos and live people. In the final experiment, viewers were asked to match a live person to a single photograph. Even under these conditions, performance was poor (c. 85%), with no advantage over matching 2 photographs. We suggest that problems of eyewitness identification may involve difficulties in initial encoding of unfamiliar faces, in addition to problems of memory for an event. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic polymorphism of apolipoprotein A-IV in the chimpanzee: common deletion of a conserved 12-nucleotide tandem repeat

Apolipoprotein A-IV (apoA-IV protein; APOA4 gene) is structurally polymorphic in various mammalian species, including human, baboon, dog, horse, and mouse. To analyze the extent of genetic variation in the chimpanzee APOA4 gene, we screened 115 common chimpanzees (Pan troglodytes) (86 unrelated wild captured parents and 29 captive-born offspring) using isoelectric focusing followed by immunoblotting for protein polymorphism and using polymerase chain reaction (PCR) assay for DNA polymorphism. At the protein level the unrelated sample of chimpanzees is highly variable, having four alleles, APOA4*1, APOA4*2, APOA4*3, and APOA4*4, with frequencies of 0.192, 0.430, 0.331, and 0.047, respectively. The chimpanzee APOA4 locus, with four common alleles and a gene diversity of 67%, is more variable than previously reported variations in baboons (five alleles with 52% gene diversity) and humans (two alleles with 15% gene diversity). PCR amplification of chimpanzee DNAs, using a pair of human oligonucleotide primers covering a region of 300 nucleotides in the third exon, revealed a common 12-nucleotide deletion (allele frequency = 0.192) that correlates exactly with the APOA4*1 allele detected by isoelectric focusing and immunoblotting. DNA sequencing of the 300-nucleotide PCR amplified product revealed the deletion of 12 nucleotides near the carboxyl terminal region of the mature apoA-IV protein. This in-frame deletion, which codes for and eliminates four amino acids [glutamic acid (GAG), glutamine (CAG), glutamine (CAG), and glutamine (CAG)], occurs in a region that is evolutionarily conserved among rats, mice, chimpanzees, and humans. The partial DNA sequencing of the 3' end of the chimpanzee APOA4 gene revealed 99% identity with the human APOA4 gene.     

Perceived differences between chimpanzee (Pan troglodytes) and human (Homo sapiens) facial expressions are related to emotional interpretation.

Human face perception is a finely tuned, specialized process. When comparing faces between species, therefore, it is essential to consider how people make these observational judgments. Comparing facial expressions may be particularly problematic, given that people tend to consider them categorically as emotional signals, which may affect how accurately specific details are processed. The bared-teeth display (BT), observed in most primates, has been proposed as a homologue of the human smile (J. A. R. A. M. van Hooff, 1972). In this study, judgments of similarity between BT displays of chimpanzees (Pan troglodytes) and human smiles varied in relation to perceived emotional valence. When a chimpanzee BT was interpreted as fearful, observers tended to underestimate the magnitude of the relationship between certain features (the extent of lip corner raise) and human smiles. These judgments may reflect the combined effects of categorical emotional perception, configural face processing, and perceptual organization in mental imagery and may demonstrate the advantages of using standardized observational methods in comparative facial expression research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Field trial to evaluate the immunogenicity of pseudorabies virus vaccines with deletions for glycoproteins G and E

This study is a geographically systematic genetic survey of the easternmost subspecies of chimpanzee, Pan troglodytes schweinfurthii. DNA was noninvasively collected in the form of shed hair from chimpanzees of known origin in Uganda, Rwanda, Tanzania, and Za?re. Two hundred sixty-two DNA sequences from hypervariable region 1 of which of the mitochondrial control region were generated. Eastern chimpanzees display levels of mitochondrial genetic variation which are low and which are similar to levels observed in humans (Homo sapiens). Also like humans, between 80% and 90% of the genetic variability within the eastern chimpanzees is apportioned within populations. Spatial autocorrelation analysis shows that genetic similarity between eastern chimpanzees decreases clinically with distance, in a pattern remarkably similar to one seen for humans separated by equivalent geographic distances. Eastern chimpanzee mismatch distributions (frequency distributions of pairwise genetic differences between individuals) are similar in shape to those for humans, implying similar population histories of recent demographic expansion. The overall pattern of genetic variability in eastern chimpanzees is consistent with the hypothesis that the subject has responded demographically to paleoclimatically driven changes in the distribution of eastern African forests during the recent Pleistocene.     

Differential use of vocal and gestural communication by chimpanzees (Pan troglodytes) in response to the attentional status of a human (Homo sapiens).

This study examined the communicative behavior of 49 captive chimpanzees (Pan troglodytes), particularly their use of vocalizations, manual gestures, and other auditory- or tactile-based behaviors as a means of gaining an inattentive audience's attention. A human (Homo sapiens) experimenter held a banana while oriented either toward or away from the chimpanzee. The chimpanzees' behavior was recorded for 60 s. Chimpanzees emitted vocalizations faster and were more likely to produce vocalizations as their 1st communicative behavior when a human was oriented away from them. Chimpanzees used manual gestures more frequently and faster when the human was oriented toward them. These results replicate the findings of earlier studies on chimpanzee gestural communication and provide new information about the intentional and functional use of their vocalizations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)