Attachment

The intense chemical reaction of passionate love cannot last forever; eventually the honeymoon ends and other chemical reactions begin to take place that result in feelings of calmness and comfort (De Boer et al, 2012). Part of this chemical reaction includes the normalizing of the hormones that once blinded people to their lover’s faults, people are now able to see their romantic partner more rationally. In reality their partner probably hasn’t changed at all, but love is no longer blind (Sukel, 2013).

Attachment is stabilized by the production of two dominant hormones, oxytocin and vasopressin (Starka, 2007; Zeki, 2007).

Oxytocin	‘the trust   hormone’ Deepens feelings of attachment and trust, both in adult   relationships as well as during mother/child bonding. Reduced anxiety,   feelings of contentment,  calmness and   security.
Vasopressin	‘the monogamy molecule’Plays an   important part in commitment and the formation of long term relationships.

The most compelling evidence that supports the importance of the role that oxytocin and vasopressin play in the attachment stage of love has been found through research into the mating habits of  the monogamous, pair-bonding rodents, the prairie voles (Carter & Getz, 1993). Prairie voles were found to have high levels of oxytocin and vasopressin present in the forebrain. Interestingly their naturally promiscuous relative, the medow vole, does not possess these high levels of vasopressin and when this single chemical was introduced into the ventral forebrain of the medow vole these rodents demonstrated a preference for monogamous behaviour (Lim, Wang, Olazabal, Ren, Terwilliger, & Young, 2004). By altering their endocrine system their natural behavioural instincts were dramatically altered.

See details of the prairie voles experiment  https://www.youtube.com/watch?v=pA4w–HP7tc

It is important to be aware that drawing conclusions of human pair-bonding behaviour based on rodent studies is tentative at best. Rodents possess different brain systems to humans, and humans are subject to a higher order of thinking than rodents for whom psychological mechanisms do not play an important role (DeBoer et al., 2012). A study conducted in 2011 into long term love and attachment was the first to demonstrate any signs of support for a correlation between the prairie-voles and human systems (Acevedo, Aron, Fisher & Browne, 2011). Regions hypothesised to be responsible for pair bonding in prairie voles showed some similarities to those in pair-bonded humans (Acevedo et al.).

Using fMRI to examine the neural correlates of long term intense romantic love researchers showed participants photographs of the loved person, an acquaintance and a neutral person. Two points of interest were notable in this study. Firstly, correlations between the questionnaires used to assess applicants for suitability and the brain areas that were activated in different individuals were examined with results demonstrating positive correlations in the following areas:

• VTA and caudate nucleus (CN) correlated with romantic love scores
• Globus pallidus (GP) correlated with friendship based love scores
• Hippocampus correlated with sexual frequency
• CN, cingulate cortex (posterior) and hippocampus (posterior) correlated with obsession.

Secondly, Acevedo et al., found correlations between the attraction and attachment stages of love in the brain (2011):

Brain areas activated during the three stages of romantic love

Lust	Attraction	Attachment	Function
	VTA	VTA	Important   in reward processing, associated with behaviours necessary for survival,Motivation,   reinforcement learning and decision making.
		Ventral   striatum	Considered   the reward centreReward   and motivation
	Dorsal   striatum – putamen and  CN	Dorsal   striatum – putamen and  CN	Important   for goal directed behaviour to attain rewards, involved with learningMotor   and cognitive controlPutamen   rich in dopamine neurotransmitters
		GP,   receives input from the striatum and putamen, and sends it to the thalamus	Mediates   both liking and wanting of rewards and motivation.Helps   to regulate smoothness of movement at a subconscious levelHigh   density of oxytocin and vasopressin receptors
Hypothalamus-   directs pituitary gland to release testosterone and oestrogen		thalamus	Maintains   homeostasis within the body,high   correlation with sexual frequencyHigh   density of oxytocin and vasopressin receptors
		substantia   nigra (SN)	Important   in reward, addiction and movementHigh   density of oxytocin and vasopressin receptors
	cingulate   cortex	cingulate   cortex	Involved with emotion   formation and processing, learning, and memory. Influential in linking   behavioural outcomes to motivationLiking   or pleasure
	Medial   insula	Medial   insula	Responsible   for emotions, sexual arousal and drug cravings
		Dorsal   raphe – receives inputs from the VTA/SN	Involved   in body’s response to pain and stress
	hippocampus	hippocampus	Commonly   known as the emotional brain
Pituitary   gland			Responsible   for the release of testosterone and oestrogen

Potentially, what this demonstrates is that although systems hypothesised to be involved with attachment were seen, correlations between the reward areas involved in the attraction stage of love remain present. It seems likely to be more of a sliding scale than a different stage altogether. Validity studies into the PLS also add some support to this theory as it was found that passionate love did appear to be affected by time with  both stage and length demonstrating significant effects (Hatfield & Sprecher, 1986). This theory also supports the idea behind the disparity in findings between Bartel and Zeki (2000) and Fishers et al’s (2004) fMRI results during the attachment phase of love.  If the amount of time spent in a relationship slowly alters the neural correlates, then the difference between Bartel’s results; taken at an average of 2.3 years into the relationship; and Fishers results; taken at an average of seven months into the relationship; would demonstrate a sliding scale from attraction to attachment, and this does in fact appear to be the case.

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