A Functional Neuro-Anatomical Model of Human Attachment (NAMA)

1. General Considerations

Attachment theory proposes the existence of an attachment behavioral system that orchestrates proximity seeking behavior, particularly in times of distress and/or need. In 2012, Patrik Vuilleumier and I proposed a first social neuroscience account of the attachment behavioral system by summarizing the to date available experimental evidence and suggesting a “functional neuro-anatomical model of the influence of adult attachment style on social processing” (Frontiers in Human Neurosciencesee here)After providing an updated version of the above-mentioned first model as part of a book chapter on “The Social Neuroscience of Attachment“ in 2017, a new review paper has just been accepted for publication in the journal Cortex. It provides an extended and refined “Functional Neuro-Anatomical Model of Human Attachment (NAMA)” – Section 2 below -, and explains its biological and neural components / modules by a newly formulated set of prototypical attachment pathways – Section 3 below.

2. Description of NAMA

Functonal neuro-anatomical model of human attachment (NAMA) – Figure 2 in Long et al., 2020. For more information, see here.

NAMA aims at providing a model for the putative biological and neural underpinnings of the attachment behavioral system in humans. To do so, NAMA differentiates between an affective evaluation (left) and a cognitive control (right) system that are in a dynamic balance (“push-pull”). While the affective evaluation system is thought to process incoming information rather quickly and automatically (i.e. bottom-up), the cognitive control system likely represents more voluntary regulatory processes that can modulate affective evaluation mechanisms (i.e. top-down). NAMA further differentiates the affective evaluation system into an aversion (red) and an approach (green) module (that also are in a dynamic balance; “push-pull”), and the cognitive control system into an emotion regulation (blue) and a mental state representation (orange) module. Finally, NAMA suggests a (non-exhaustive) list of involved brain circuits for each module & system, and a (non-exhaustive) list of involved neurotransmitters / -peptides. For an explanation of abbreviations, please see here.

The so far available data (mainly from adults) suggest that the organized attachment orientations / classifications of insecure-avoidant and insecure-anxious (as compared to secure) differentially influence affective evaluation and cognitive control mechanisms. While both insecure attachment orientations appear to (at least partially) interfere with emotion (self-)regulation mechanisms as part of the cognitive control system (see also here), attachment avoidance and anxiety seem to have opposite effects on affective evaluation processes. Attachment avoidance may be mainly associated with a general blunting of affective evaluation processes, particularly in the case of positive social information (neurally represented in the approach module). In turn, attachment anxiety may be mainly linked to a general intensification of affective evaluation processes, especially in the case of negative social information (neurally represented in the aversion module). The above said, interesting additional and more complex interactions are starting to emerge. For a more comprehensive picture, please refer to Figure 3 in Long et al. (in press).

As NAMA is only concerned with the three organized attachment orientations of security, avoidance and anxiety, we just submitted a first attempt to extend NAMA to attachment disorganization and trauma (“A Functional Neuro-Anatomical Model of Disorganized Attachment – NAMDA“). More information on NAMDA will be made available here as soon as possible.

3. The Underlying Prototypical Attachment Pathways of NAMA

Prototypical attachment pathways – Figure 1 in Long et al., 2020. For more information, see here.

The two components / four modules of NAMA explained in section 2 are conceptually derived from an initial prototypical attachment pathway – see the light orange path (A) in the Figure above.

The attachment behavioral system is thought to become activated most prominently and strongly by an (external or internal) event (E) that is appraised as threatening (and thus deemed salient / relevant for the organism at a given moment in time). Consequently, the event (E) triggers an appropriate fear response that entails a deviation from (physiological and psychological) homeostasis. Threat detection and the fear response are likely biologically and neurally maintained by the aversion module of NAMA.

As a core element of attachment, the innate response to threat / fear is physical proximity seeking behavior to establish closeness to a significant other. Such social approach behavior is likely biologically and neurally maintained by the approach module of NAMA.

If proximity seeking is successful (and the source of threat / danger removed), the next step in the attachment behavioral system can occur: social co-regulation of emotion through allostasis. Although initially mainly externally driven, this step becomes increasingly autonomous (i.e. self-regulation) and is likely biologically and neurally maintained by the emotion (self-)regulation module of NAMA.

If co-regulation is successful, the organism can return to physiological homeostasis. Likely biologically and neurally encoded as a subjectively positive experience, this positive experience of the return to homeostasis is accompanied by a felt sense of security conveyed through the soothing and comforting social interaction as part of social co-regulation. Such socially rewarding experience is likely once more biologically and neurally encoded by the approach module of NAMA.

Finally, through repeated cycles of the above-described prototypical initial attachment pathway, predictions about the own capacity to elicit help and the availability and responsiveness of others in times of need start emerging. These are the fundamental building blocks of internal working models (IWMs) of attachment. IWMs are likely neurally maintained by the mental state representation module of NAMA.

As derivatives of the prototypical initial attachment pathway (A), NAMA comprises suggestions of alterations associated with attachment security (B), avoidance (C) and anxiety (D). These derivatives reflect the primary attachment strategy of (physical and psychological) proximity seeking in the case of security (B), the secondary attachment strategy of de-activation in the case of avoidance (C), and the secondary attachment strategy of hyper-activation in the case of anxiety (D). Please note that the IWMs of anxiety should read – Self -; Others +/-. This will be implemented / amended during proofing in the original article.

4. Additional Considerations

4.1 Different Neuro-Biological Accounts of Human Attachment

It should be mentioned here that there are other neurobiological accounts of human attachment available in the literature. A nice summary can be found in a book chapter by Gillath, Karantzas, & Fraley (2016): “What Can Neuroscience, Genetics, and Physiology Tell Us About Attachment?“.

In our view, one prominent account by Helen Fisher (see, for example, here) suggests that three principal human social behaviors can be dissociated by their underlying neurotransmitter / -peptide systems: (1) the sex drive / lust mediated by androgens, (2) attraction / mate choice / romantic love mediated by catecholamines, and (3) attachment (understood as a long-term non-sexual bond between individuals; child-parent, but also romantic partners, etc.) mediated by oxytocin.

A second prominent account by Ruth Feldman (for a recent review, see here) suggests a differentiation of human attachment behaviors by means of four principal mammalian bonds, namely: (1) parent-infant bonds, (2) pair-bonds, (3) peer bonds, and (4) bonds between conspecifics. Furthermore, Ruth Feldman proposes that the strenght of these bonds can be categorically distinguished by their degree of bio-behavioral synchrony expressed within the bond – with parent-infant bonds having the strongest degree of bio-behavioral synchrony.

In our above-described functional neuro-anatomical model of human attachment (NAMA) we propose, the models by Fisher and Feldman are also considered. These models, however, are extended by the notion put forward by attachment theory that the very same mammalian bond / attachment  – mediated by the very same neurotransmitter / -peptide systems – can be subjected to strong inter-individual differences depending on the quality of the bond and thus attachment. For example, parent-infant bonds may be generally characterized by high bio-behavioral synchrony and prominently mediated by oxytocin, but strong inter-individual differences in the bio-behavioral signature are to be expected depending on the quality of the bond – the latter being reflected in secure versus insecure, anxious and/or avoidant attachment orientations / classifications (not only on the individual but also the dyadic and family level). Inter-individual differences therefore are key in NAMA and we are particularly interested in describing their influence on the psychological, behavioral, biological, physiological, and neural basis of human attachment.