Emotion expression surely must be central to regulating social relationships, as Vigil contends. For internal psychological functions such as ratcheting up attention to strategic interference (Buss Reference Buss1989) or recalibrating internal mechanisms (Tooby & Cosmides Reference Tooby, Cosmides, Lewis, Haviland-Jones and Barrett2008), overt expression of internal emotional states would be superfluous, although of course these ultimately often contribute to the solution of social adaptive problems. Vigil also makes a compelling case for the role of emotions in signaling reciprocity potential. I propose that emotion expressions serve other functions as well, and I highlight one suite that has been relatively neglected by emotion theorists – their role in adaptations for exploitation.
Buss and Duntley (Reference Buss and Duntley2008) argue that humans have evolved three fundamental strategies for acquiring reproductively relevant resources: (1) individual resource acquisition strategies (e.g., solo hunting or gathering), (2) cooperative resource-acquisition strategies (e.g., forming reciprocal and coalitional alliances), and (3) exploitative resource-acquisition strategies (e.g., expropriating the resources of others through deception, theft, coercion, terror, force, or murder). Although cooperative strategies have enjoyed a large volume of theoretical and research attention, exploitative strategies have been relatively ignored, with some notable exceptions (e.g., Buss & Duntley Reference Buss and Duntley2008; Jones Reference Jones2007; Zuk & Kolluru Reference Zuk and Kolluru1998).
Without diminishing the role of emotion expression in strategies of reciprocity, I suggest that emotion expressions play a key role in strategies of exploitation and anti-exploitation defenses. Ominous expressions of anger, for example, could signal a perceived violation of reciprocity in one context, but signal a threat to a victim to cede resources immediately and non-reciprocally as a strategy of exploitation. Women may express an emotion of sexual desire to deepen a committed relationship in one context, or to expropriate a man's resources non-reciprocally through a “bait-and-switch” strategy in another context (Buss Reference Buss2003).
Emotion expressions also function as anti-exploitability defenses. Displays of anger or masculine prowess may signal reciprocal resource capacity, but may also convey to would-be exploiters that one is a poor choice as a potential victim of exploitation. Expressions of jealousy, to take another example, may signal to romantic partners a lack of exploitability as a potential cuckold.
The intentional suppression of emotion expression, too, may figure centrally in anti-exploitability defenses. The suppression of subjectively experienced jealousy to one's intimate partner, for example, may function to conceal an exploitable mate-value discrepancy that otherwise might be perceived by a romantic partner (Buss Reference Buss2000). The suppression of fear in the presence of coalitional partners may function not merely to signal reciprocity capacity, but also to activate exploitability adaptations in coalition partners in order to better expropriate out-group resources. Even displays of kindness and sympathy, rather than signaling reciprocity capacity, may function in some circumstances to deactivate the evolved anti-exploitability defenses in others.
A comprehensive theory of emotion expressions must explain their role in the successful enactment of adaptations for exploitation, as well as their functions in signaling non-vulnerability to those pursuing exploitative resource acquisition strategies.
