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Lisa A Parr

Publications and source records attributed to Lisa A Parr.

9 recordsLinked to original sources
PubMed2006

Three studies on configural face processing by chimpanzees.

Previous studies have demonstrated the sensitivity of chimpanzees to facial configurations. Three studies further these findings by showing this sensitivity to be specific to second-order relational properties. In humans, this type of configural processing requires prolonged experience and enables subordinate-level discriminations of many individuals. Chimpanzees showed evidence of a composite-like effect for conspecific but not human faces despite extensive experience with humans. Chimpanzee face recognition was impaired only when manipulations targeted second-order properties. Finally, face processing was impaired when individual features were blurred through pixelation. Results confirm that chimpanzee face discrimination, like humans, depends on the integrity of second-order relational properties.

Analysis of Variance↗
PubMed2006

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.

Action Potentials↗
PubMed2006

Muscles of facial expression in the chimpanzee (Pan troglodytes): descriptive, comparative and phylogenetic contexts.

Facial expressions are a critical mode of non-vocal communication for many mammals, particularly non-human primates. Although chimpanzees (Pan troglodytes) have an elaborate repertoire of facial signals, little is known about the facial expression (i.e. mimetic) musculature underlying these movements, especially when compared with some other catarrhines. Here we present a detailed description of the facial muscles of the chimpanzee, framed in comparative and phylogenetic contexts, through the dissection of preserved faces using a novel approach. The arrangement and appearance of muscles were noted and compared with previous studies of chimpanzees and with prosimians, cercopithecoids and humans. The results showed 23 mimetic muscles in P. troglodytes, including a thin sphincter colli muscle, reported previously only in adult prosimians, a bi-layered zygomaticus major muscle and a distinct risorius muscle. The presence of these muscles in such definition supports previous studies that describe an elaborate and highly graded facial communication system in this species that remains qualitatively different from that reported for other non-human primate species. In addition, there are minimal anatomical differences between chimpanzees and humans, contrary to conclusions from previous studies. These results amplify the importance of understanding facial musculature in primate taxa, which may hold great taxonomic value.

Animal Communication↗
PubMed2005

Emotional communication in primates: implications for neurobiology.

The social brain hypothesis proposes that large neocortex size in Homonoids evolved to cope with the increasing demands of complex group living and greater numbers of interindividual relationships. Group living requires that individuals communicate effectively about environmental and internal events. Recent data have highlighted the complexity of chimpanzee communication, including graded facial expressions and referential vocalizations. Among Hominoids, elaborate facial communication is accompanied by specializations in brain areas controlling facial movement. Finally, the evolution of empathy, or emotional awareness, might have a neural basis in specialized cells in the neocortex, that is, spindle cells that have been associated with self-conscious emotions, and mirror neurons that have recently been shown to activate in response to communicative facial gestures.

Animals↗
PubMed2004

Perceptual biases for multimodal cues in chimpanzee (Pan troglodytes) affect recognition.

The ability of organisms to discriminate social signals, such as affective displays, using different sensory modalities is important for social communication. However, a major problem for understanding the evolution and integration of multimodal signals is determining how humans and animals attend to different sensory modalities, and these different modalities contribute to the perception and categorization of social signals. Using a matching-to-sample procedure, chimpanzees discriminated videos of conspecifics' facial expressions that contained only auditory or only visual cues by selecting one of two facial expression photographs that matched the expression category represented by the sample. Other videos were edited to contain incongruent sensory cues, i.e., visual features of one expression but auditory features of another. In these cases, subjects were free to select the expression that matched either the auditory or visual modality, whichever was more salient for that expression type. Results showed that chimpanzees were able to discriminate facial expressions using only auditory or visual cues, and when these modalities were mixed. However, in these latter trials, depending on the expression category, clear preferences for either the visual or auditory modality emerged. Pant-hoots and play faces were discriminated preferentially using the auditory modality, while screams were discriminated preferentially using the visual modality. Therefore, depending on the type of expressive display, the auditory and visual modalities were differentially salient in ways that appear consistent with the ethological importance of that display's social function.

Acoustic Stimulation↗
PubMed2004

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.

Animals↗
PubMed2003

The discrimination of faces and their emotional content by chimpanzees (Pan troglodytes).

The ability to recognize and discriminate conspecific faces and facial expressions has played a critical role in the evolution of social communication. Darwin was one of the first to speculate that human and nonhuman primate facial expressions share similar mechanisms for production and functions in expressing emotion. Since his seminal publication, numerous studies have attempted to unravel the meaning of animal signals, with the most success coming from the field of vocal communication, where researchers have identified the referential and emotional nature of specific vocalizations. Studies specifically addressing nonverbal facial displays, however, have faced numerous methodological challenges, including how to objectively describe facial movements and how to study the perception and production of these signals within a social context. In this paper, I will review my studies on chimpanzee face recognition, their ability to categorize facial expressions, and the extent to which chimpanzee facial expressions may convey information about emotion. Finally, recent studies from my lab have begun to address the role of auditory and visual cues in facial expression categorization. Chimpanzees were given the task of matching expressions according to which sensory modality was more salient, the visual or auditory component. For some expressions the visual modality was preferred, while for others the auditory modality was preferred. These data suggest that different social and ecological pressures may shift attention towards one sensory modality over another, such as during long-distance communication or emotional conflict.

Affect↗
PubMed2002

Acoustic startle, prepulse inhibition, and fear-potentiated startle measured in rhesus monkeys.

BACKGROUND: Modulation of the acoustic startle response is a simple and objective indicator of emotionality and attention in rodents and humans. This finding has proven extremely valuable for analysis of neural systems associated with fear and anxiety. Until recently, there have been few efforts to develop acoustic startle measurement in nonhuman primates. We report here development of a whole-body acoustic startle protocol in rhesus monkeys. METHODS: Eight juvenile rhesus monkeys were tested in a new whole-body (somatic) acoustic startle protocol. Startle responses were assessed in three paradigms: 1) stimulus intensity-response amplitude, 2) prepulse inhibition (PPI), and 3) fear-potentiated startle. RESULTS: Initial studies revealed that the amplitude of whole-body startle in monkeys, as in rodents and humans, is directly proportional to acoustic stimulus intensity and gradually habituates with repeated exposures. Presentation of a weak acoustic stimulus 45-2020 msec before a startle stimulus reduces startle amplitude by 40%-50%, depending on interstimulus interval length (PPI). We have also measured significant potentiated startle amplitude in the presence of a visual stimulus after pairing it with an inescapable pulse of pressurized air (fear-potentiated startle). CONCLUSIONS: Our data demonstrate that acoustic startle in nonhuman primates successfully bridges rodent and human research in two broad areas: stimulus-response relationships and behavioral plasticity represented by habituation, PPI, and fear potentiation. The opportunity now emerges to link concepts developed in rodents to the more complex neuroanatomical and cognitive processes common to monkeys and humans.

Acoustic Stimulation↗