Tuesday, December 2, 2008

Facial mobility aids group cohesion

My article entitled "Socioecological correlates of facial mobility in nonhuman anthropoids" has been accepted for publication in the American Journal of Physical Anthropology. Here's the abstract:

Facial mobility, or the variety of facial movements a species can produce, is likely influenced by selection for facial expression in diurnal anthropoids. The purpose of this study is to examine socioecological correlates of facial mobility independent of body size, focusing on social group size and arboreality as possible evolutionary agents. Group size was chosen because facial expressions are important for group cohesion, while arboreality may limit the utility of facial expressions. Data for 12 nonhuman anthropoid species were taken from previous studies and analyzed using a phylogenetic generalized least-squares approach. Regression results indicate that group size is a good predictor of facial mobility independent of body size. No statistical support was found for the hypothesis that arboreality constrains the evolution of facial mobility. The correlation between facial mobility and group size may be a consequence of selection for more effective facial expression to help manage conflicts and facilitate bonding in larger groups. These findings support the hypothesis that the ultimate function of facial expression is related to group cohesion.

*UPDATE (2/24/09): The publisher's version of this article is now online
here (subscription required). Contact me if you want a PDF.

Tuesday, October 21, 2008

Discover Magazine Article

Renowned science journalist Carl Zimmer has recently published an article on facial expression in Discover Magazine. The article describes my own research on facial mobility, as well as research by Bridget Waller and Anne Burrows.

Tuesday, September 9, 2008

Valley News Story


My research was featured in the September 8, 2008 edition of the Valley News, a local newspaper covering the upper Connecticut river valley of Vermont/New Hampshire.

The accompanying photograph of me in the field (above) was taken by Aliza Le Roux.

Monday, August 25, 2008

IPS Edinburgh 2008

I presented a paper at the 2008 meeting of the International Primatological Society entitled "Facial expression and social organization in Macaca: a phylogenetic comparative analysis." My presentation was part of a symposium on facial expression entitled "Facial expression in primates: measurement, meaning and function." Here is a description of the symposium:

Primates send and receive an array of facial signals in order to navigate their social environments, and these communicative systems have undoubtedly been influential in the evolution of both primate mind and society. Yet facial expression is a relatively understudied mode of primate communication. Several recent developments have increased our understanding of facial signals, in terms of what they communicate, how they interact with other communicative modalites and how they have evolved. In this symposium, scientists studying facial expression in primates (including humans) from a variety of different perspectives will present their theoretical positions, methodological innovations and recent findings. The overarching goals are to present the form and function of facial expressions in different species, examine different approaches in the study of facial expression, and ultimately to identify the specific role facial expressions play in the lives of primates.

The symposium was organized by Bridget Waller, Sarah-Jane Vick, and Lisa Parr. The other participants included Jan van Hooff, Karen Schmidt, Amy Pollick, Elisabetta Palagi, and Matthew Campbell.

Tuesday, June 24, 2008

Allometry of facial mobility

My paper entitled "Allometry of facial mobility in anthropoid primates: implications for the evolution of facial expression" is now in press at the American Journal of Physical Anthropology. Here's the abstract:

Body size may be an important factor influencing the evolution of facial expression in anthropoid primates due to allometric constraints on the perception of facial movements. Given this hypothesis, I tested the prediction that observed facial mobility is positively correlated with body size in a comparative sample of nonhuman anthropoids. Facial mobility, or the variety of facial movements a species can produce, was estimated using a novel application of the Facial Action Coding System (FACS). I used FACS to estimate facial mobility in 12 nonhuman anthropoid species, based on video recordings of facial activity in zoo animals. Body mass data were taken from the literature. I used phylogenetic generalized least squares (PGLS) to perform a multiple regression analysis with facial mobility as the dependent variable and two independent variables: log body mass and dummy-coded infraorder. Together, body mass and infraorder explain 92% of the variance in facial mobility. However, the partial effect of body mass is much stronger than for infraorder. The results of my study suggest that allometry is an important constraint on the evolution of facial mobility, which may limit the complexity of facial expression in smaller species. More work is needed to clarify the perceptual bases of this allometric pattern.

UPDATE (8/25/08): The publisher's version of this paper is now available online here (subscription required). Contact me if you want a PDF.

Wednesday, June 4, 2008

Gelada Fieldwork





I spent six weeks in the Simien Mountains of Ethiopia this Spring studying the social behavior and communication of gelada baboons. This is the preliminary phase of a larger project investigating the motivational contexts and social functions of facial expression in male geladas. My collaborators are Drs. Jacinta Beehner and Thore Bergman of the University of Michigan Gelada Research Project.

UPDATE (7/21/08): Picture of me in the field courtesy of Dave Pappano.

AAPA 2008

At this year's annual meeting of the American Association of Physical Anthropologists, I presented on the allometry of facial mobility in a symposium focusing on the muscles of facial expression. The symposium was organized by Karen Schmidt and Anne Burrows. Here's the description:

The State of the Face: An Evolutionary Update on the Muscles of Facial Expression
The structure and function of the face have long been of interest to biological anthropologists because of its pivotal role in behavioral, cognitive, and sensory adaptations. The evolution of the muscles of facial expression specifically, however, has been relatively neglected in primate and human evolutionary studies despite the role of these muscles in nonverbal communication as well as in articulatory movements of speech, audition, olfaction, tactile exploration, and social interaction. The goal of this symposium is to draw together researchers currently studying the evolution of the muscles of facial expression from comparative, developmental, histological, anatomical, and behavioral perspectives to update the biological anthropological understanding of the face. A secondary goal is to identify novel evolutionary interpretations of the structure and function of the muscles of facial expression, in both human and nonhuman primates. The role of adaptational processes in the development of species-specific features of the facial musculature will be addressed. Recent work in nonhuman primates as well as in humans will be incorporated. We also aim to identify new avenues of understanding the face that incorporate both communicative and noncommunicative functions of the muscles of facial expression and closely associated structures.

Some of the other presenters included Lisa Parr and Bridget Waller of the ChimpFACS project.

Saturday, March 15, 2008

NEAA 2008

I presented a paper entitled "Allometry of facial mobility in anthropoid primates" at the 2008 meeting of the Northeastern Anthropological Association in Amherst, MA. Here's the abstract:

Body size is likely to be an important constraint on the evolution of facial expression in primates. This is because facial movements are more difficult to discern in smaller species. I tested the hypothesis that facial mobility is positively correlated with body size in a comparative sample of nonhuman anthropoids. Facial mobility, or the variety of facial movements a species can produce, was estimated using the human Facial Action Coding System (FACS). I used FACS to estimate facial mobility in 12 nonhuman anthropoid species, based on video recordings of facial activity in zoo animals. Body mass data were taken from the literature. I performed a multiple regression analysis with facial mobility as the dependent variable and two independent variables: log body mass and dummy-coded infraorder. Together, body mass and infraorder explain 92% of the variance in facial mobility. However, the partial effect of body mass is much stronger than for infraorder. The results of my study suggest that allometry is an important constraint on the evolution of facial mobility, which may explain why smaller taxa tend to exhibit fewer facial displays than larger taxa. More work is needed to clarify the structural bases of this allometric pattern.

Some of the other folks in my session were Richard Lawler and Stacey Matarazzo.