Research Overview:

I investigate fundamental questions about the emergence and utility of nonverbal behavior for the communication of emotion, personality, and social rank. I rely on a variety of methods, including structured group interactions, human-robot interactions, experiments, and longitudinal designs, while leveraging different measurement and analytical techniques including automated and manual nonverbal behavioral coding, peer-reports, machine learning, and psychophysiology. To examine the generalizability of my research findings, I explore these questions around the globe and across ages, including in non-western and small-scale traditional societies, and children as young as two.

Ongoing Research:

What do our smiles reveal?

In our modern world filled with screens and selfies, smiles are ubiquitously posed for photographs that are used for social networking (Facebook, Instagram), professional development (LinkedIn), and virtual dating (Bumble, Tinder). Yet not all smiles are the same: Subtle variations can be observed in the specific facial muscles people use to configure their posed smile, and the intensity of each facial muscle activation. My current research goes beyond the conventional understanding of smiles as mere expressions of spontaneously felt positive emotion, instead establishing them as a form of self-expression that, when posed, offers a valid window into well-being and personality, and enables accurate assessments of dispositions by machine-learning algorithms and lay observers. This can revolutionize the landscape of well-being and mental health assessment; posed smiles may serve as a viable and readily accessible tool for detecting those who may benefit from well-being or mental health resources.

Past Research:

distinct nonverbal displays of Dominance and Prestige

Evidence from psychology, organizational behavior, anthropology, and evolutionary biology has converged to suggest that humans use two distinct strategies to attain social rank and influence others: dominance, which involves the use of aggression and intimidation to elicit fear and forced deference, and prestige, which involves the demonstration of knowledge and expertise to elicit respect and freely conferred deference.  I uncovered the first evidence that dominance and prestige are associated with distinct sets of nonverbal behavior, which are spontaneously demonstrated by leaders, and enable them to effectively guide the judgments and decision making of team members (Witkower, Tracy, Cheng, & Henrich, 2020, Journal of Personality and Social Psychology). Building on this work, I recently uncovered evidence that nonverbal displays of dominance and prestige are widely generalizable and potentially universal features of human communication (Witkower, Hill, Koster, & Tracy, under review).

The Action Unit Imposter

I proposed the action unit imposter account (Witkower & Tracy, 2019, Psychological Science), which argues that certain head movements co-opt the psychology of facial-expression perception by creating the visual illusion of facial dynamics. Specifically, when the head is tilted down, the eyebrows appear to lower and take on a V-shape. These appearance cues are nearly identical to those that result from activating the corrugator facial muscle (i.e., Action Unit 4 in FACS, or AU4), which is a movement associated with the communication of dominance and threat across cultures and ages. Tilting one’s head downward therefore serves as an “action-unit imposter”, increasing perceptions of dominance by changing the appearance of the face with no facial muscle movement. The action unit imposter account is a widely-generalizable and possibly universal visual mechanism guiding human perception (Witkower, Hill, Koster, & Tracy, 2022, Scientific Reports). It is critical for emotion communication (Witkower & Tracy, 2020, Emotion).

Bodily expression of emotion

Research examining nonverbal communication often focuses on facial expressions. This is for good reason, as facial expressions are valuable tools for social communication (e.g., Witkower, Lange, & Tracy, in prep; Witkower, Rule, Tracy, 2022; Emotion; Witkower, Rule, Tracy, 2022; under review). However, nonverbal behaviors that go beyond the face, especially those involving body movements, also provide valuable social information. This is because bodily expressions enable interpersonal communication when when the face is obscured (e.g., medical masks) or turned away, and across large distances. In my work I demonstrate that the body can effectively communicate emotion (Witkower & Tracy, 2019, Emotion Review), and that bodily expressions of emotion generalize across diverse populations (Witkower, Hill, Koster, & Tracy, 2021, Affective Science) and ages (Witkower, Tracy, Pun, & Baron, 2021, Journal of Nonverbal Behavior).

Future Research:

Smiles are a window into our personality

People ubiquitously smile during brief interactions and first encounters, and when posing for photos that are used for virtual dating, social networking, and professional profiles. Yet not all smiles are the same: subtle individual differences can be observed in how people pose their smile. In this line of work, I am demonstrating that the specific configuration of facial muscles people use to form their smile, and the intensity of those facial muscle activations, leak information about their conscientiousness, aggression, arrogance, warmth, and trustworthiness. Furthermore, given that smiles contain information diagnostic of personality, observers viewing smiling faces are able to form (slightly) more accurate judgments about people when viewing their smiling faces, when compared to viewing their neutral faces. Smiles may therefore be a window that reveals our personality.

Building on this work, I am taking a machine learning approach to assess how accurately personality, mental health, and future behavior can be detected from a single photograph of a person’s smile.

Angularity is a foundation of human threat communication

For decades researchers have documented the precise nonverbal behaviors that humans use to communicate threat. Yet it remains largely unknown why any particular behavior or display leads to reliable perceptions of threat, and what the vast suite of threat-communicating behaviors have in common. One possibility is that humans evolved to associate geometric angularity with threat and danger (e.g., sharp and angular = dangerous), and that this cognitive association over time became co-opted for the nonverbal communication of threat, such that humans today leverage a variety of threat-signaling behaviors that function by increasing the visual angularity of facial and bodily and features. In recent work, I am demonstrating that individuals’ association between geometric angularity and danger indexes their perception of prototypical human threat expressions as dangerous, across all visual channels of nonverbal communication: facial expressions, head movements, and bodily expressions. Furthermore, these effects generalize to at least three different countries on three different continents – USA, India, and South Africa – providing evidence for the generalizability of our account and suggesting that angularity may lie at the foundation of humans’ nonverbal threat communication.

Building on this work, I am currently developing a tool that automates the measurement of angularity for specific facial regions, which will enable researchers to further pinpoint the impact of facial angularity on nonverbal expression and perception in their own work.