New Developments in Understanding Emotional Facial Signals in Chimpanzees

ABSTRACT— There has been little research over the past few decades focusing on similarities and differences in the form and function of emotional signals in nonhuman primates, or whether these communication systems are homologous with those of humans. This is, in part, due to the fact that detailed and objective measurement tools to answer such questions have not been systematically developed for nonhuman primate research. Despite this, emotion research in humans has benefited for over 30 years from an objective, anatomically based facial-measurement tool: the Facial Action Coding System (FACS). In collaboration with other researchers, we have now developed a similar system for chimpanzees (ChimpFACS) and, in the process, have made exciting new discoveries regarding chimpanzees' perception and categorization of emotional facial expressions and similarities in the facial anatomy of chimpanzees and humans, and we have identified homologous facial movements in the two species. Investigating similarities and differences in primate emotional communication systems is essential if we are to understand unique evolutionary specializations among different species.     

Cognitive and physiological markers of emotional awareness in chimpanzees (Pan troglodytes)

The ability to understand emotion in others is one of the most important factors involved in regulating social interactions in primates. Such emotional awareness functions to coordinate activity among group members, enable the formation of long-lasting individual relationships, and facilitate the pursuit of shared interests. Despite these important evolutionary implications, comparative studies of emotional processing in humans and great apes are practically nonexistent, constituting a major gap in our understanding of the extent to which emotional awareness has played an important role in shaping human behavior and societies. This paper presents the results of two experiments that examine chimpanzees' responses to emotional stimuli. First, changes in peripheral skin temperature were measured while subjects viewed three categories of emotionally negative video scenes; conspecifics being injected with needles (INJ), darts and needles alone (DART), and conspecific directing agonism towards the veterinarians (CHASE). Second, chimpanzees were required to use facial expressions to categorize emotional video scenes, i.e., favorite food and objects and veterinarian procedures, according to their positive and negative valence. With no prior training, subjects spontaneously matched the emotional videos to conspecific facial expressions according to their shared emotional meaning, indicating that chimpanzee facial expressions are processed emotionally, as are human expressions. Decreases in peripheral skin temperature, indicative of negative sympathetic arousal, were significantly lower when subjects viewed the INJ and DART videos, compared to the CHASE videos, indicating greater negative arousal when viewing conspecifics being injected with needles, and needles themselves, than when viewing conspecifics engaged in general agonism. Accepted after revision: 8 April 2001 ❚ Electronic Publication     

Counselor Competency in the Courtroom

This article outlines general courtroom procedures and offers systematic practical advice for the counselor testifying as an expert witness. Major topics include the counselor role in court, preparing for testimony, answering questions, and dealing with the cross-examination.     

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.     

Intramuscular electrical stimulation of facial muscles in humans and chimpanzees: Duchenne revisited and extended

The pioneering work of Duchenne (1862/1990) was replicated in humans using intramuscular electrical stimulation and extended to another species (Pan troglodytes: chimpanzees) to facilitate comparative facial expression research. Intramuscular electrical stimulation, in contrast to the original surface stimulation, offers the opportunity to activate individual muscles as opposed to groups of muscles. In humans, stimulation resulted in appearance changes in line with Facial Action Coding System (FACS) action units (AUs), and chimpanzee facial musculature displayed functional similarity to human facial musculature. The present results provide objective identification of the muscle substrate of human and chimpanzee facial expressions- data that will be useful in providing a common language to compare the units of human and chimpanzee facial expression.     

Visual kin recognition and family resemblance in chimpanzees (Pan troglodytes)

The male-offspring biased visual kin recognition in chimpanzees (Pan troglodytes) reported by L. A. Parr and F. B. M. de Waal (1999) was replicated with human (Homo sapiens) participants and a principal components analysis (PCA) of pixel maps of the chimpanzee face photos. With the same original materials and methods, both humans and the PCA produced the same asymmetry in kin recognition as found with the chimpanzees. The PCA suggested that the asymmetry was a function of differences in the distribution of global characteristics associated with the framing of the faces in the son and daughter test sets. Eliminating potential framing biases, either by cropping the photos tightly to the faces or by rebalancing the recognition foils, eliminated the asymmetry but not human participants' ability to recognize chimpanzee kin.     

Risk and protective factors for suicide among Guyanese youth: Youth and stakeholder perspectives

Guyana, a low-to-middle-income country (LMIC) in South America, leads the world in youth suicide. As an understanding of risk and protective factors is critical to the development of culturally informed suicide prevention efforts, research exploring these factors among youth in Guyana is needed. The current study expands on current research on adolescent suicide in Guyana and LMICs broadly by using qualitative focus groups and interviews to explore adult stakeholders' and youth's perspectives. Participants included 17 adult stakeholders and 40 adolescents in Guyana. Data were analysed using a grounded theory approach. Themes related to participants' perceptions of risk factors for suicide included demographic characteristics, pressure and expectations, adults' responses to youth, limited coping with stressful life events and exposure to suicide. Themes related to protective factors for suicide included positive social support and involvement in community activities. Findings have implications for the development and tailoring of suicide prevention efforts for Guyanese youth.     

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.     

Set-size and Frequency-of-occurrence Judgements in Young and Older Adults: The Role of the Availability Heuristic

Two experiments examined the cognitive processes underlying judgements of set size and judgements of frequency of occurrence in young (Experiments 1 and 2) and older (Experiment 2) adults. Previous research has implicated the availability heuristic in set-size judgements, whereas an automatic processing mechanism has been implicated in judgements of frequency of occurrence. In the current experiments, path analysis was employed to investigate the role of an availability bias in performance on the judgement tasks. In Experiments 1 and 2, both types of judgement were influenced by repetition frequency of words independent of the availability (recall) of specific exemplars. Experiment 2 extended the investigation to include age differences. Although older adults' recall performance was poorer overall, the availability bias was age invariant, and there were no age differences in either set-size or frequency-of-occurrence judgements. Our results indicate that both set-size and frequency-of-occurrence judgements are independent of the availability bias evident in recall, and they support the notion that an automatic processing mechanism underlies both types of judgement.     

The role of sincere amends and perceived partner responsiveness in forgiveness

In a sample of 188 people currently in a romantic relationship, the authors examined the extent to which perceiving a partner as responsive and sincere in making amends relates to participants' forgiveness of a partner after a real‐life hurtful event. Specifically, it was predicted that sincere amends would be associated with greater forgiveness because it conveys that one's partner has understood and validated one's experience of the hurtful event. Results supported this mediational model. Further, exploratory analyses suggested that this meditational model is moderated by event severity and relationship satisfaction. Discussion focuses on understanding how this work might help to inform the dynamic process of forgiveness in couples.