The Steroid/Peptide Theory of Social Bonds: Integrating testosterone and peptide responses for classifying social behavioral contexts

TLDR: The Steroid/Peptide Theory of Social Bonds (S/P Theory), which integrates T and peptides to provide a model, set of predictions, and classification system for social behavioral contexts related to social bonds, is presented.

About: This article is published in Psychoneuroendocrinology.The article was published on 2011-10-01 and is currently open access. It has received 251 citations till now. The article focuses on the topics: Aggression & Poison control.

Figures

Figure 3. The Steroid/Peptide Model of Social Bonds. This model demonstrates pathways from aggression and intimacy to T, AVP, and OT and how these hormones in turn affect social bonding. We partition aggression into antagonistic and protective aggression; both types increase testosterone (T), but only protective aggression increases vasopressin (AVP), while antagonistic aggression decreases or has no effect on AVP. We partition intimacy into sexual and nurturant intimacy; both types increase oxytocin (OT), but only sexual intimacy increases T, while nurturant intimacy decreases T. OT and AVP promote, while T inhibits, social bonding. Aggression involves direct conflict that is instigated to be (1) antagonistic: obtaining new territory, status, mates, dominance, etc.; (2) protective: protecting or safeguarding social bonds, e.g. infant defense, partner/mate guarding or defense, etc. Only AVP can be used to distinguish aggression types, since both increase T. Intimacy involves direct close physical contact that is (1) sexual: sexual contact between individuals that may be oriented around pleasure, reproduction, power, etc.; (2) nurturant: warm loving contact between individuals that enhances social bonds. Only T can be used to distinguish intimacy types, since both increase OT. AVP and OT are represented separately for visual purposes, but likely overlap with each other to a large extent (also possibly with PRL); estradiol may also work similarly to OT, and progesterone to AVP. “+” indicates a positive effect; “–“ indicates a negative effect.

Figure 5. The percent change in testosterone (T) in response to exercise, intercourse, and cuddling, with standard error bars. The dashed line indicates 0% change, or no change; points above this line indicate an increase in T from baseline, while points below this line indicate decreases in T from baseline. “*” indicates a significant difference at p < .05; “<” indicates a trend for a statistical difference at p < .10. Adapted with permission from van Anders et al. (2007).

Figure 4. Steroid/Peptide Framework of Social Bonds. This framework lays out a conceptual map of behavioral contexts relevant to social bonds linked to high and low T and OT. The lighter boxes are associated with social bond facilitation/promotion; the darker boxes are associated with the inhibition/dysregulation of social bonds. The framework is divided into a top section for T (social goals) and a bottom section for OT (bonding goals), with the left column for high levels and the right column for low levels of each hormone. The boxes immediately below the high/low T/OT represent the “kind” of behavioral context, or role, for that level of that hormone. Below, at the lowest level for each hormone, are smaller boxes representing a nonexhaustive list of examples of each kind/role.

Figure 1. Examples of pair bonds in multiple configurations: (a) “two-point,” as is typically conceptualized, where each individual is in only one pair bond; (b) “embedded twopoint” for L and N, where L and N are in only one pair bond each, but their partner is not exclusively bonded to them; “multi-point” for M, where M has two pair bonds, and each of these pair bond partners is pair bonded only with M; and (c) “embedded two-point” for L and N; “embedded multi-point” for M and P, where M and P have two pair bonds each, which include a mixture of partners exclusively bonded with them and bonded with others. Letters represent separate individuals, and arrows represent the direction of the bond. An example of (b) is polygyny or polyandry, and of (c) is polyamory for individuals M and P (and potentially L and N, depending on definitions).

Table 1. The steroid/peptide matrix of social bonds. Up and down arrows are relative to population norms but could relate to individual norms as well. “T” indicates testosterone.

Figure 2. Ultimate functions and proximate mechanisms of pair and parent-offspring bonds. Predictions based on this model would be (1) if pair and parent-offspring bonds elicit similar hormonal responses, then a shared evolutionary history is supported and (2) if sexual and nurturant intimacy within pair bonds elicit divergent hormonal responses,

Frequently asked questions

Q1. What are examples of nurturant behavioral contexts?

Actual examples of nurturant behavioral contexts could include grooming, feeding, pair bond existence, huddling, and other close warm contact. 

Q2. What is the role of hormones in the evolution of pair bonds?

Given that parent-offspring bonds are likely to be evolutionarily older, pair bonds may be predicated upon a neuroendocrine system that evolved to support parent-offspring bonds but in general promotes nurturance (Fisher, 1992; Carter, 1998; Fernandez-Duque et al., 2009). 

Q3. What did the authors test in the follow-up study?

The authors used the S/P Theory to develop a hypothesis about the tricky behavioral context of cuddling, a hypothesis which the authors tested in a follow-up study. 

Q4. What is the definition of pair bonds?

Like others, the authors define pair bonds as long-lasting affiliations involving intimacy, sexualcontact, preferential proximity, and emotional attachment with relative exclusivity (Hawkes, 2004). 

Q5. What is the role of OT in human social bonds?

Actual examples of social bonding could include sexual intimacy, nurturant intimacy, loneliness (i.e., the need for social bonding), social conflict resolution (e.g., arguments with loved ones that arise out a of need to strengthen a bond), etc. Consistent with the above, OT facilitates social cognitions and empathy in humans (Bos et al., 2011). 

Q6. What are the characteristics of pair bonds?

They are generally defined by social and sexual “monogamy,” and though extra-pair sexual contacts occur, pair bonds still limit sexual access to others. 

Q7. What is the importance of incorporating T into research on intimacies?

Their example with cuddling highlights the importance of incorporating T into research on intimacies, even though intimacy is typically studied only in conjunction with peptides, and T is only studied in conjunction with competition. 

Q8. What is the reasoning for a low T nurturant behavior?

This reasoning should apply only to partner cuddling, and the authors predict that parent-child cuddling should decrease T as a low T nurturant behavior (unless it is experienced as infant defense, which should accordingly increase T; a testable viable alternative hypothesis). 

Q9. What is the role of OT in social bonding?

Though findings link high OT with pair bonds and partner closeness, other research demonstrates a complementary role for OT, that is, as tied to the need or desire for social bonds. 

Q10. What is the relationship between low T and nurturance?

Low T is related to nurturance, i.e. social behavioral contexts that involve loving warm contact with others (e.g. partners/mates, offspring, friends, etc.) (and this may possibly transpire via conversation of T to estradiol, and estrogenic facilitation of peptides). 

Q11. What is the role of T in the evolution of pair bonds?

T is a favorable candidate for testing these distinct evolutionary functions, since it is positively linked to sexuality but negatively linked to nurturance (van Anders and Watson, 2006b; Ziegler et al., 2009), and because it is so strongly implicated in tradeoffs relevant to pair bonding (Wingfield et al., 1990; Ketterson et al., 2005; Bales et al., 2006; van Anders and Watson, 2006b).