Motivation and emotion/Book/2013/Oxytocin and emotion

Oxytocin and emotion:
What is the role of oxytocin in emotion?

Multimedia presentation (5 min)

Overview

A mother bonding with her baby

Oxytocin is a nonapeptide hormone which is secreted from the posterior pituitary gland and acts primarily on the hypothalamus and areas of the nervous system involved in the experience of emotion. It is primarily concerned with sexual reproduction, particularly during and after childbirth, and it is the primary hormone involved in lactation and mother-child bonding. Oxytocin is also important to the formation and maintenance of human bonds and relationships, as well as in the experience of many emotions, including empathy, trust, sexual arousal, feelings of well-being, and the reduction of stress (Carter et al., 2007). Because of oxytocin's integral role in the formation of human bonds, it is often referred to as the love or bonding hormone.

Evolution

Just as the fight or flight response is an evolutionary mechanism to cope with a stressor, so is the tend and befriend response. Where the fight or flight response is governed primarily by adrenaline, the tend and befriend response is produced by the secretion of oxytocin. Instead of a surge of adrenaline flooding an individual's body, priming the body either to fight the threat or flee from it, the tend and befriend response produces a significant amount of oxytocin, encouraging the individual to, as the name suggests, tend to and befriend others in order to alleviate the threat. Taylor et al. (2000) state that females are more likely to engage in this potentially less harmful response, as opposed to choosing to fight the threat. Evolutionarily speaking, given that females have been the primary caregivers to offspring, Taylor et al. suggest that this response was a way of protecting both the offspring and the female caregiver from harm, thereby promoting the continuation of the species.

Additionally, there are important evolutionary advantages to oxytocin as a bonding hormone (Cloke, 2009). Given that many early civilisations faced the constant threat of wild animals and attacks by other groups, bonding between individuals in a group was extremely important as it provided them with the safety of numbers, as well as the advantage of being able to hunt in a group, giving them a better chance of securing a meal (Taylor et al., 2000).

Oxytocin's role in emotion

Trust

Zak, Kurzband, and Matznere (2005) conducted a study into the effects of oxytocin on trust using monetary transfers between two volunteers. The study involved the volunteers being divided into pairs. One participant in each pair was then asked to transfer some or all of $10 they had received as incentive to participate to the other member of their pair via computer. They were told that the amount they chose to transfer would be tripled and put into the other participant's account. The second participant was then asked to transfer an amount (they could choose to send nothing if they chose) back to the first participant in their pair. Blood was drawn from each participant after each decision and oxytocin levels were measured. The results showed that participants who had received a greater portion of money from their partner had higher levels of oxytocin. It may be that oxytocin levels are elevated by trustworthy behaviour, or, as this study would suggest, trustworthy behaviour increases as oxytocin levels increase. Although it is not clear the direction of this relationship, the results indicate a strong relationship between oxytocin and trust, as well as reciprocity.

Another study in 2005 by Kosfeld, Heinrichs, Zak, Fischbacher, and Fehr used a similar method. One participant in each pair was assigned to the role of investor, while the other was assigned the role of trustee. Both the investors and trustees were then administered a dose of oxytocin via a nasal spray. The investor was then asked to transfer an amount of money via computer to the trustee and, while initially only the trustee would benefit from the transaction, the amount available to be distributed would increase through the transaction and the trustee could then choose to transfer some or none of the money back to the investor.

Empathy

Oxytocin has been shown to increase feelings of empathy towards others. Zak, Stanton, and Ahmadi conducted another study involving monetary transfers in 2007 where they increased oxytocin levels in a group of volunteers through the administration of a nasal spray containing oxytocin. After receiving treatment, the volunteers were asked to split a sum of money with a stranger they could not see and had never met. They found that those who received the oxytocin treatment were 80% more generous and displayed a greater level of empathy than those who only received the placebo. One obvious explanation for this finding is that oxytocin, as a hormone involved in bonding, makes individuals feel happier and closer to another person, even one they may not have previously met. This would make them more likely to be more generous. Zak, Stanton, and Ahmadi (2007) also suggest another explanation, which is that oxytocin reduces stress and anxiety, which results in the

Affection for another person can be expressed by kissing

individual feeling less anxious about giving up resources like money. The study also tested the effects of oxytocin on altruism. Although an increase in altruistic behaviour in general was not directly associated with an increase in oxytocin levels, generosity, which was defined as a subset of altruism, seemed to be influenced significantly by the increase in oxytocin.

Love and romance

It has been hypothesised that oxytocin as a bonding hormone is important in relationship between two partners as a way to ensure the ideal environment for raising offspring (Gonzaga, Turner, Keltner, Campos, & Altemus, 2006). For example, a 1998 study conducted by Carter into pair bonding between two species of voles in North America. The study found that the prairie vole, which pair bonds for life and is monogamous and sociable, had higher levels of oxytocin (and more oxytocin receptors), while the closely related montane vole, which are solitary and not monogamous, had lower levels of oxytocin and fewer oxytocin receptors.

Similarly, high levels of oxytocin have been found to be present in people who report greater satisfaction with and quality of their relationships (Gouina et al., 2010). Research has found that these individuals often report a greater level of support from their partner and a higher rate of physical intimacy (e.g. hugs, kisses, massages) with their partner (Gouina et al, 2010). Gouina et al. (2010) found in their study into marital behaviours and oxytocin levels that those individuals who had higher levels of oxytocin displayed more positive communication behaviours during a social support task with their spouse than those with lower oxytocin levels. The results showed no differences in oxytocin levels between males and females, which is consistent with other studies in this area (e.g. Ditzen et al., 2009). Complementary to these findings, Gonzaga et al. (2006) found in a study that nonverbal displays of love caused an increase in oxytocin levels in both partners.

Stress management and fear

Oxytocin appears to have an attenuating effect on stress and fear. It has been found in several studies that oxytocin seems to have several anxiety relieving effects among rats administered oxytocin, including sedation, reducing fear, and decreasing activity in the sympathetic nervous system (Uvnas-Moberg, 1997, as cited in Taylor et al., 2000). These results would seem to suggest it has an inhibitory effect on hormones such as adrenaline that are involved in stress reactions like the fight-or-flight response. Again, this response appears to be stronger in females than males, for a number of reasons (Taylor et al., 2000). First, females release more oxytocin in response to stress than do males (Jezova, Jurankova, Mosnarova, Kriska, & Skultetyova, 1996). Second, oxytocin release is inhibited by androgens, which are more common in males (Jezova et al., 1996). Finally, oxytocin and its effects are strongly influenced by the presence of estrogen (McCarthy, 1995, as cited in Taylor et al., 2000).

Another study by Windle, Shanks, Lightman, and Ingram (1997) found that rats treated with oxytocin showed dose dependent reduction of cortisol production in response to stress. The same study also found that rather than a sedative effect, the oxytocin administered to the rats had a specifically anxiolytic effect as the activity of the rats did not decrease after receiving the dose of oxytocin.

Aggression

Oxytocin appears to have an inhibitory effect on aggression (Witt et al., 1990). Witt et al. (1990) conducted a study, again on prairie voles, which found that after administration of oxytocin, female aggression declined significantly. There was no such decline seen in males administered oxytocin. One possible explanation for this is that testosterone levels are much higher in males than in females, which results in higher levels of aggression in males. Females seem to have both a higher level of oxytocin and a lower level of testosterone to begin with, which would explain this disparity between the two sexes.

Involvement in psychiatric disorders

An autistic boy obsessively stacking cans

Oxytocin, or the lack thereof, has been implicated as being one of the primary factors behind psychiatric disorders, such as autism and Asperger's syndrome, schizophrenia, anxiety, and borderline personality disorder (Meyer-Lindenberg, Domes, Kirsch, & Heinrichs, 2011).

Autism

Autism is one psychiatric disorder in which patients display lower than normal levels of oxytocin (Meyer-Lindenberg et al., 2011). One of the most recognisable symptoms of autism is the impairment of normal social interaction. Autistic children particularly are known to display social behaviours that are against the norm, such as unwillingness to share or take turns, and a deficiency in their ability to form attachments to others, maintain eye contact, and recognise facial expressions and emotions. Individuals with autism will also typically display compulsive and ritualistic behaviours, such as lining up or stacking items in a certain order. It has been suggested that autistic people may have a deficiency or abnormality in their oxytocin levels. This suggestion was supported by a study by Modahl et al. (1998) in which it was found that autistic children with significant levels of social impairment had much lower oxytocin levels than those children who showed no social impairment.

Schizophrenia

Oxytocin deficiency has also been identified as a possible cause of schizophrenia (Meyer-Lindenberg et al., 2011). People with schizophrenia, as in autistic individuals, are often unable to discern facial emotions, an ability which is partially controlled by oxytocin. A study by Goldman, Marlow O’Connor, Torres, and Carter (2008) found that people diagnosed with schizophrenia had lower levels of oxytocin than the healthy controls and, when administered a dose of oxytocin, were better able to identify facial emotions.

Relationship with vasopressin

Vasopressin appears to be something of an antithesis of oxytocin. Vasopressin is concerned primarily with social behaviours that are generally seen as typically male, such as aggression (Heinrichs, von Dawans, & Domes, 2009) and territorial behaviour (Carter, 1998). Interestingly, vasopressin is very similar in structure to oxytocin. It too is a nonapeptide, differing from oxytocin by just two amino acids (Jin, Macbeth, Pagani, & Young, 2009). In a number of the studies already mentioned (Windle et al., 1997; Goldman et al., 2008), as oxytocin levels rise, vasopressin levels seem to drop, and vice versa, suggesting that the two are directly involved in the fine balance of social behaviours like stress, fear, aggression, and trust.

Applications

Treatment of psychiatric disorders

As already discussed, oxytocin has the potential to revolutionise the treatment of psychiatric disorders like autism and schizophrenia. For example, Guastella et al. (2010) conducted a study to determine the effects of a nasal spray containing oxytocin on the symptoms of autism. Before and after administration of the oxytocin, the participants were given a task that involved attempting to 'read the mind' of a person in a photograph and name the emotion they were expressing. The results showed that after receiving the oxytocin, the participants could more easily recognise and name the emotions presented. This suggests that oxytocin may be an effective treatment for autism spectrum disorders that involve social impairment.

Additionally, given that it has a positive effect on feelings of trust and the ability to recognise facial emotions, oxytocin has also been proposed as a potential treatment for paranoid schizophrenia (Feifel et al., 2010). Feifel et al. (2010) conducted a study into the use of oxytocin as a treatment for the disorder. They found that after three weeks of daily doses of oxytocin via a nasal spray, the participants had significantly reduced symptoms. This suggests oxytocin possesses antipsychotic properties that could be well utilised as a treatment for schizophrenia.

Conflict

One potentially invaluable application of the knowledge about oxytocin and its effects on emotion is in conflict. Shamay-Tsoory et al. (2013) state that conflict is largely driven by a lack of empathy towards an out-group (the enemy). Shamay-Tsoory et al. investigated the role of hormones like oxytocin in feelings of empathy between two conflicting social groups, the Israelis and Palestinians. They found that Israelis who received doses of oxytocin displayed a significant increase in empathy towards Palestinians. These results suggest that if oxytocin, when introduced into a situation as hostile as the Israel-Palestine conflict, is capable of stimulating such a major change in empathy towards a group an individual has likely grown up being taught to hate, it is hard to think of a conflict situation in which it would not be beneficial.

Other applications

Oxytocin could also be used as a way to reduce aggression in people more prone to outbursts of aggression, specifically young men. It could also be used as a medication to relieve stress.

Conclusion

Oxytocin has been shown to be an important part of the chemistry of emotion. Aside from its historical delegation as a female only hormone, concerned with labour and lactation, it plays an integral role in in both sexes in the production and maintenance of emotions such as empathy, trust, and love, and also in the reduction of stress, fear, and aggression. Research has demonstrated it also plays an important part in psychiatric disorders involving social impairment, such as autism and schizophrenia, and it is this fact that could potentially be used to create an effective treatment for these conditions. Further research should focus on the implications of such an application, as well as other potential applications like reducing aggression in young men and acting as a stress alleviator.

Quiz time!

References

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External links

Paul Zak: Trust, Morality and Oxytocin (TED Talk)