Likewise, if in the moment of generation of her (psycho-emotional) direct reward the woman is not tied-up because of a failed compatibility test, the relational exchange will generate indirect reward for the man, who will consequently go for a complementary direct (that is, sexual) reward, which will, however, not be granted by the non-compatible F-RA of the woman, who could refuse the inappropriate moves of the man. In this case, the flow of rewards will break down whenever the cycle reaches the woman’s F-RA, staying confined within the psycho-emotional sphere. The re-iteration of this situation will also lead in this case to the cycle’s dissolution, because of the systematic frustration of the man’s sexual expectations, inducing the latter to quit the relationship, or because of the growing unease of the woman toward a relationship that, not being fed by her switched-off F-RA, entails a progressive deterioration of her direct rewards, as they are accompanied by an unpleasant, more or less explicit request for sexual attentions.
The process that leads to the building of the TUs through the interlocking of male and female direct and indirect rewards with their different nature can also be regarded as an incentivization of within-couple male–female super-cooperation-that is, an unconditional reciprocal commitment to reward the other both in sexual and in psycho-emotional terms as part of the couple bond . This form of super-cooperation, by shifting the partners’ focus from self-centered to other-centered goals and benefits, has multiple adaptive implications: Securing a favorable environment for joint effective parenting ; eliciting mutual trust and self-sacrifice for the sake of the other ; improving the couple’s resilience ; favoring cultural transmission of pro-social traits ; and even promoting the human development of both partners .
The specific structure of the active and receptive areas in men and women, and in particular their dimorphism and positioning within the TU-C, therefore offer an adaptive solution to the problem of female–male cooperation related to the formation of the monogamic heterosexual couple
However, as for all forms of cooperation, however sophisticated, the structure of the TU-C allows opportunistic subjects who are able to manipulate it to obtain short-term benefits, which also include the woman’s impregnation outside the stable monogamous couple. The selective capacity of the TU-C is linked to its iteration: Long-term stable couples will be able to iteratively travel along the TU-C for a long time, whereas short-term ones will only go through it for a limited number of iterations, or will even (dynamically) confine themselves to a portion of the cycle without completing a full iteration. In this way, the TU-C favors the emergence of stable monogamic couples without jeopardizing the possibility of impregnation in non-stable couples or outside a proper couple. The dynamics of a well-functioning TU-C may also be temporarily supported by a single partner due to its own inertia, which leads a partner to reward the other even in the temporary absence of reciprocity, and may in the limit keep on operating even in the case of a critical situation that is common to both partners, such as the loss of a child.
In stable monogamic couples, the TU-C also allows another important form of resilience: That against all those situations that compromise for relatively long periods a partner’s capacity to reward the other, such as incidents or invalidating illnesses or psychological suffering
The TU-C may then be evolutionarily characterized as an incentive compatible dynamic relational mechanism for tied-up potential partners, that is, it will be traveled along and iterated in a sustainable way only by those partners who receive a constant flow of mutually reinforcing direct and indirect rewards. A non-tied-up subject may simulate the TU and persist in the TU-C to reap personal benefits (for instance, if the other partner is rich, powerful, or socially desirable), but will have to manage an escalating conflict with her/his own non-excited RA, which fails to provide any indirect reward, thus calling for an effort, which in the long term is not sustainable, to constantly simulate a gratification that is instead real for actually tied-up partners. Other non-tied-up subjects who do not get special personal benefits from the persistence in the TU-C will limit themselves to openly manifest their opportunistic attitudes, trying to exploit the tied-up partner on the relevant level for their own AA, or they will simply quit the cycle. It is, however, important to underline how, unlike the simplest asymmetric information models, the incentive compatibility of the TU-C does not consist here in the discrimination of given behavioral types (for instance, subjects oriented toward short-term vs. long-term mating). In other words, a subject who might not be interested in persisting in the TU-C with a certain partner (to whom for instance s/he is not tied-up) might instead find her/himself persisting in another TU-C with a different partner to whom s/he gets tied-up. Subjects cannot be categorically classified as short-term vs. long-term oriented, even when their AA expresses itself in these terms, but will always contextually define their orientation with respect to a specific potential partner facing them.