Despite a staggering body of research demonstrating sex differences in expressed emotion, very few theoretical models (evolutionary or non-evolutionary) offer a critical examination of the adaptive nature of such differences. From the perspective of a socio-relational framework, emotive behaviors evolved to promote the attraction and aversion of different types of relationships by advertising the two most parsimonious properties of reciprocity potential, or perceived attractiveness as a prospective social partner. These are the individual's (a) perceived capacity or ability to provide expedient resources, or to inflict immediate harm onto others, and their (b) perceived trustworthiness or probability of actually reciprocating altruism (Vigil 2007). Depending on the unique social demands and relational constraints that each sex evolved, individuals should be sensitive to advertise “capacity” and “trustworthiness” cues through selective displays of dominant versus submissive and masculine versus feminine emotive behaviors, respectively. In this article, I introduce the basic theoretical assumptions and hypotheses of the framework, and show how the models provide a solid scaffold with which to begin to interpret common sex differences in the emotional development literature. I conclude by describing how the framework can be used to predict condition-based and situation-based variation in affect and other forms of expressive behaviors.

We suggest that the framework proposed by Vigil is useful in laboratory contexts but might come up short for in vivo social interactions. Emotions result from cost-benefits trade-offs but are not solely generated at the individual level to establish emotional social spheres. In organizational contexts, emotion expression can be a constitutive part of a professional activity, and observed sex differences might vanish.

Emotion expression serves functions in exploitative resource-acquisition strategies that may not include relationship reciprocity. These include rendering victims more exploitable and signaling one's status as non-exploitable. A comprehensive theory of emotion expressions must explain their role in adaptations for exploitation, as well as evolved defenses against those pursuing a strategy of exploitation.

Biofeedback mechanisms (a) between individuals, (b) between the individual and the society structures which shape individual cognitions, and (c) within the individual genetic biochemical circulation, may explain the diversity of trustworthiness potential and the option of mutual trust for every individual in any given society.

Vigil's socio-relational framework of sex differences in emotional expressiveness emphasizes general sex differences in emotional responding, but largely ignores the social context in which emotions are expressed. There is much empirical evidence showing that sex differences in emotion displays are flexible and a function of specific social roles and demands, rather than a reflection of evolutionary-based social adjustments.

In this commentary, we review evidence that production-based (perceiver-independent) measures reveal few consistent sex differences in emotion. Further, sex differences in perceiver-based measures can be attributed to retrospective or dispositional biases. We end by discussing an alternative view that women might appear to be more emotional because they are more facile with emotion language.

Vigil's socio-relational framework of sex differences in emotion-expressive behavior has a number of interesting aspects, especially the principal concepts of reciprocity potential and perceived attractiveness and trustworthiness. These are attractive and potentially heuristic ideas. However, some of his arguments and claims are not well grounded in research on early development. Three- to five-year-old children did not show the sex differences in emotion-expressive behavior discussed in the target article. Our data suggest that Vigil may have underestimated the roles of epigenetic and cultural factors in shaping emotion-expressive behavior.

Humor and social dilemmas are two disparate areas that have been linked to emotions. However, they tend to have been studied apart from considerations of emotion and emotional expression. We provide an overview of how such areas might be illuminated by Vigil's socio-relational framework, and how capacity and trustworthiness are communicated in humor and social dilemmas.

One facet of Vigil's socio-relational framework of expressive behaviors (SRFB) suggests that females are more sensitive to facial expressions than are males, and should detect facial expressions more quickly. A re-examination of recent research with children demonstrates that girls do detect various facial expressions more quickly than do boys. Although this provides support for SRFB, further examination of SRFB in children would lend important support this evolutionary-based theory.

Vigil summarizes sex-related differences in emotivity, and presents a psychological model based on the restrictive assumption that responses to stimuli are dichotomous. The model uses for support the concept of intrasexual selection, but ignores intersexual selection. An alternative hypothesis might be that emotivity signals age: maturity in men and youth in women. Integration requires considering all evolutionary biology, not just agreeable concepts.

In this commentary, the idea of reciprocity potential indicators is tied in with ultimate accounts on sex differences in social sensitivity. It is proposed that, rather than crying, smiling is a more likely cooperative signal. The possibility of coevolution and polymorphism in perceptual and signalling systems are also discussed briefly, with a reference to Theory of Mind and Machiavellianism.

A sex difference in the tendency to outbreed (female exogamy) is a premise for the target article's proposed framework, which receives some support by being shared with chimpanzees but not with more distantly related primates. Further empirical support is provided, and it is suggested that recognition of sex differences might improve effective fairness, taking sexual assault as a case in point.

Laughing, humor, and tickling, but not tearing and crying, involve the give-and-take that provides value and a basis for exchange in the psychosexual marketplace.

Parent-infant emotional expressions vary according to parent and infant gender. Such parent-infant interactions critically affect infant development. Neuroimaging research is exploring emotion-related brain function that varies according to gender, and regulates parenting thoughts and behaviors in the early postpartum. Through specific brain functions, parenting serves to program the infant brain for the next generation of sex-specific emotional expression.

The two-dimensional model of social relations outlined in the target article has striking convergence with empirically derived dimensional models of interpersonal perception, inter-group perception, and face evaluation. All these models posit two-dimensional structures related to perceptions of valence/affiliation and power/status. Although these models are parsimonious, they may be insufficient to account for behaviors in specific contexts.

We present evidence that smiling is positively associated with positive affect in women and negatively associated with negative affect in men. In line with Vigil's model, we propose that, in women, smiling signals warmth (trustworthiness cues), which attracts fewer and more intimate relationships, whereas in men, smiling signals confidence and lack of self-doubt (capacity cues), which attracts numerous, less-intimate relationships.

Vigil suggests that expressed emotions are inherently learned and triggered in social contexts. A strict reading of this account is not consistent with the findings that individuals, even those who are congenitally blind, do express emotions in the absence of an audience. Rather, grounded cognition suggests that facial expressions might also be an embodied support used to represent emotional information.

In addition to the socio-relational framework of expressive behaviors (SRFB), we recommend integrating theoretical and empirical findings based on attachment theory. We advocate a dynamic interpretation of early caregiver–child interaction. The consequences of models from developmental psychology for the occurrence of psychopathology are demonstrated from a clinical perspective.

According to socio-relational theory, men and women encountered different ecologies in their evolutionary past, and, as a result of different ancestral selection pressures, they developed different patterns of emotional expressivity that have persisted across cultures and large human evolutionary time scales. We question these assumptions, and propose that social-cognitive models of individual differences more parsimoniously account for sex differences in emotional expressivity.

This response shows how the socio-relational framework of expressive behaviors may be used to understand and predict social psychological processes, beyond sex differences in the expression of emotion. I use this opportunity to elaborate on several key concepts on the epigenesis of evolved social behaviors that were not fully addressed in the target article. These are: evidence of a natural history of masculine and feminine specialization (sect. R1); phenotypic plasticity and range of reactivity of social behaviors (sect. R2); exploitive and protective functions of social behaviors (sect. R3); and the role of cognition in some affective responses (sect. R4). I conclude by highlighting (in sect. R5) future directions for psychological research from a socio-relational basis.