Recent application of theories of embodied or grounded cognition to the recognition and interpretation of facial expression of emotion has led to an explosion of research in psychology and the neurosciences. However, despite the accelerating number of reported findings, it remains unclear how the many component processes of emotion and their neural mechanisms actually support embodied simulation. Equally unclear is what triggers the use of embodied simulation versus perceptual or conceptual strategies in determining meaning. The present article integrates behavioral research from social psychology with recent research in neurosciences in order to provide coherence to the extant and future research on this topic. The roles of several of the brain's reward systems, and the amygdala, somatosensory cortices, and motor centers are examined. These are then linked to behavioral and brain research on facial mimicry and eye gaze. Articulation of the mediators and moderators of facial mimicry and gaze are particularly useful in guiding interpretation of relevant findings from neurosciences. Finally, a model of the processing of the smile, the most complex of the facial expressions, is presented as a means to illustrate how to advance the application of theories of embodied cognition in the study of facial expression of emotion.

According to the SIMS model, mimicry and simulation contribute to perceivers' understanding of smiles. We argue that similar mechanisms are involved in comprehending the hand gestures that people produce when speaking. Viewing gestures may elicit overt mimicry, or may evoke corresponding simulations in the minds of addressees. These real or simulated actions contribute to addressees' comprehension of speakers' gestures.

Niedenthal et al. present a model for embodied emotion simulation and expression understanding that spans multiple brain systems. This commentary addresses the potential role of time in this model, and its implications for understanding social dysfunction.

The SIMS model offers an embodied perspective to cognition and behaviour that can be applied to organizational studies. This model enriches behavioural and brain research conducted by social scientists on emotional work (also known as emotional labour) by including the key role played by body-related aspects in interpersonal exchanges. Nevertheless, one could also study a more vocal aspect to smiling as illustrated by the development of “smile down the phone” strategies in organizations. We propose to gather face-to-face and voice-to-voice interactions in an embodied perspective taking into account Lakoff and Johnson's (1980) theory of conceptual metaphors.

The assumption that a complex and fuzzy notion like smile can be the basis of a scientific, rather than semantic, inquiry can only lead to confused and inconclusive results. It would be more productive to start with the well-defined and measurable patterns of the clearly visible contrasts that are produced on the human face by various muscular contractions around the white patches formed by the sclera and the teeth. These features are universal, whereas a common word, in whatever language, is necessarily ambiguous, culture-dependent, and historically rather than biologically determined.

The embodied simulation of smiles involves motor activity that often changes the perceivers' own emotional experience (e.g., smiling can make us feel happy). Although Niedenthal et al. mention this possibility, the psychological processes by which embodiment changes emotions and their consequences for processing other emotions are not discussed in the target article's review. We argue that understanding the processes initiated by embodiment is important for a complete understanding of the effects of embodiment on emotion perception.

Understanding the very nature of the smile with an integrative approach and a novel model is a fertile ground for a new theoretical vision and insights. However, from this perspective, I challenge the authors to integrate culture and race in their model, because both factors would impact upon the embodying and decoding of facial expressions.

Smiling can be interpreted as a costly signal of future benefits from cooperation between the individual smiling and the individual to whom the smile is directed. The target article by Niedenthal et al. gives little attention to the possible mechanisms by which smiling may have evolved. In our view, there are strong reasons to think that smiling has the key characteristics of a costly signal.

This commentary raises general questions about the parsimony and generalizability of the SIMS model, before interrogating the specific roles that the amygdala and eye contact play in it. Additionally, this situates the SIMS model alongside another model of facial expression processing, with a view to incorporating individual differences in emotion perception.

We argue that the meaning of smiles is interpreted from physical/contextual cues, and simulation may simply reinforce the information derived from these cues. We suggest that, contrary to the claim of the SIMS model, positive and negative smiles may invoke similar simulation processes. Finally, we provide alternative explanations for the role of eye contact in the processing of smiles.

Niedenthal et al. discuss the importance of eye gaze in embodied simulation and, more globally, in the processing of emotional visual stimulation (such as facial expression). In this commentary, we illustrate the relationship between oriented eye movements, consciousness, and emotion by using the case of severely brain-injured patients recovering from coma (i.e., vegetative and minimally conscious patients).

Niedenthal et al. postulate that eye contact with the expresser of an emotion automatically initiates embodied simulation. Our commentary explores the generality of such an eye contact effect for emotions other than happiness. Based on the appraisal theory of emotion, we propose that embodied simulation may be reinforced by mutual or averted gaze as a function of emotional context.

Niedenthal et al. recognize that cultural differences are important when interpreting facial expressions. Nonetheless, many of their core observations derive more from individualistic cultures than from collectivist cultures. We discuss two examples from the latter: (1) lower rates of mutual eye contact, and (2) the ubiquity of specific “functional smiles.” These examples suggest constraints on the assumptions and applicability of the SIMS model.

We outline three possible shortcomings of the SIMS model and specify these by applying the model to autism. First, the SIMS model assigns a causal role to brain processes, thereby excluding individual and situational factors. Second, there is no room for subjective and high-level conceptual processes in the model. Third, disentangling the different stages in the model is very difficult.

We question two conceptual assumptions made by Niedenthal et al.: the dichotomy between true and false smiles and the close tie between recognition and experience of emotion. An excessive dependence on everyday language suggests overly parsimonious accounts of a complex set of relations between smile, experience, and context.

We focus on the role that motor mimicry plays in the SIMS model when interpreting whether a facial emotional expression is appropriate to an eliciting context. Based on our research, we find general support for the SIMS model in these situations, but with some qualifications on how disruption of motor mimicry as a process relates to speed and accuracy in judgments.

A complete model of smile interpretation needs to incorporate its social context. We argue that embodied simulation is an unlikely route for understanding dominance smiles, which typically occur in the context of power. We support this argument by discussing the lack of eye contact with dominant faces and the facial and postural complementarity, rather than mimicry, that pervades hierarchical relationships.

The SIMS model claims that it is by means of an embodied simulation that we determine the meaning of an observed smile. This suggests that crucial interpretative work is done in the mapping that takes us from a perceived smile to the activation of one's own facial musculature. How is this mapping achieved? Might it depend upon a prior interpretation arrived at on the basis of perceptual and contextual information?

We propose the SIMS model can be strengthened by detailing the dynamic interaction between sensorimotor activation and contextual conceptual information. Rapidly activated evaluations and contextual knowledge can guide and constrain embodied simulations. In addition, we stress the potential importance of extending the SIMS model to dynamic social interactions that go beyond the passive observer.

Previous studies with Westerners have found that both the mouth and eyes are crucial in identifying and interpreting smiles. We proposed that Easterners (e.g., Chinese and Japanese) evaluate the role of the mouth and eyes in smiles differently from Westerners. Individuals in collectivistic Eastern society heavily rely on information from the eyes to identify and interpret the meaning of smiles.