It probably comes as no surprise to you that individual personality traits influence your emotional bonds with people, as well as your reactions to people in your social environment. Psychologists like to call this adult attachment. These traits can have pretty big influences on your sensitivity to social signals of things like support or conflict. So if you have one type of personality, you may be more sensitive to people who are showing support, while other kinds of personality may ignore the supporting people and be more sensitive to those who are offering conflict (which I like to call being bitter). But the question remained as to HOW these social signals were processed in the brain, and what made the social signals different in people with different personalities. Does someone who looks for support have different neural wiring than someone who looks for conflict?
The authors of this experiment used fMRI (functional Magnetic Resonance Imaging) to study differences in personality and their reactions to certain kinds of social stimuli. First, they settled on three classic kinds of attachment style; secure, avoidant, and anxious. People with secure attachment style report positive and trustful interactions with others. Those with avoidant attachment styles prefer to be distance and detached, don’t really feel a need for close relationships, and tend to distrust social overtures from others. Finally, people with anxious attachment style perceive others as unresponsive or untrustworthy and worry more about social rejection. Obviously not all people fall neatly into these three categories, most people are somewhere in between. But these three main types clearly have differences in the way they react to social overtures, would their brains react the same way?
The researchers used two different social cues, a smiling face and an angry face, as well as a feedback message about how the subject was doing in a perceptual task. The smiling or angry faces were paired with “won” or “lost” paradigms. So in each test, the task would end up something like this:
1a) Participant does the task (estimating the number of dots), then they get a screen that says “you won!” with a smiling face. This implies that the person who is smiling is happy that you won and is cooperating with you.
1b) Participant does the task, then they get a screen saying “you won!” with an angry face. This implies that the person who is angry is working against or competing with you, and is not happy that you’re winning.
Of course this works the opposite way with losing scenarios, when an angry face would be one that is cooperating with you (what they call a congruent condition), and a smiling one that is happy you lost and competing with you (what they call an incongruent condition). So you get four total feedback states. The scientists then measured brain responses to each feedback type.
(As a side note: All these tests with faces and trials were conducted inside the MRI, with personality testing before and after to determine which of the groups the participant belonged to. I’ve been in an MRI multiple times in my career as a guinea pig, and if you’re interested and you qualify, you should try it and help neuroscience! It’s not harmful, and you often get paid for your time, though I warn you the inside of an MRI is both boring and loud. And if you’re very lucky, they let you see pics of your own brain!!)
They found that certain areas of the brain lit up in each scenario, but the DEGREE that they lit up was correlated with different personality types. For instance, a positive feedback (a smiling face for a win) activated areas of the brain associated with reward processing, the striatum and the ventral tegmental area. So getting positive social feedback from someone makes you feel good. But people with avoidant personality types didn’t light up as much as those with other personality types, indicating that avoidant personalities are not as sensitive to social reward.
Conversely, when participants got a negative response (an angry face associated with a win), their amygdala lit up, an area associated with fear processing. This means that participants reacted with fear (or probably just vigilance or wariness) to negative social feedback. And this response was increased in people with anxious personalities, meaning that they had increased sensitivity to the possibility of social punishment. People with secure attachment lit up in the VTA with positive feedback, but didn’t light up as much to the possibility of social punishment, meaning they were more sensitive to reward and less sensitive to punishment than their anxious or avoidant counterparts.
The results of this study have several interesting implications. First, it is the first study to show that brain responses to facial expressions in humans are influenced by the social meaning of the facial expression. A smile is not always a good thing, and our brains can tell the difference between a smile of support and a smile that is happy we lost. Also, though your amygdala does react in general to negative facial expressions, the degree of the response will depend a lot on whether or not that anger is directed at you, or on your behalf.
But what the authors thought of as the really important finding was that differences in adult attachment style, and thus differences in personality, have a big impact on how your brain reacts to social situations, and they not only found that we HAVE a reaction, they found out WHERE some of these reactions were coming from, and that reactions in several places are different depending on your personality.
Their data are given additional strength because the brain area changes they found correlated well with the types of personality difference. People of avoidant personality types did not have as much of a positive reaction (activation in the striatum and ventral tegmental area) as those with anxious or secure personalities, meaning that they don’t rely so much on expressions of social support from others. People of secure personality had high reactions of positive feedback, and relatively low reactions to negative feedback, implying that they have stronger positive reactions to social support than they do negative reactions to punishment. Finally, people with anxious attachment styles have an increased reaction to punishment (an increased reaction in the amygdala), implying that they place more importance on social punishment than people with avoidant or secure personalities.
This has some pretty wide implications. This could mean that distinct neural connections and neurochemical patterns could underlie attachments in different personality types. It is also one of the first studies to tke a brain region-specific response and link it to something as specific as social meaning in facial expression. The scientists also point out that this is the first direct evidence that there are two independant affective dimensions (reward and fear), and responses to these two dimensions are characteristic of individual personality traits. But what I like best about this paper is that it takes a behavior (in this case the reaction to positive or negative feedback) and finds a basis for it in the brain.
I know to some people the results of this study sound like psycho-philosophy, people sitting around wondering why personalities are different from each other, but actually this could help us discover differences that can contribute to things like autism (which can result in avoidant personality), phobias and high anxiety personalities, and what it is that makes for a secure attachment. Also, now that we have different areas of the brain localized and know that they respond individually to different stimulations, we could study those areas to try and find treatments for those who may have problems related to them (such as anxiety, PTSD, and phobias).
VrtiÄka, P., Andersson, F., Grandjean, D., Sander, D., Vuilleumier, P., Zak, P. (2008). Individual Attachment Style Modulates Human Amygdala and Striatum Activation during Social Appraisal. PLoS ONE, 3(8), e2868. DOI: 10.1371/journal.pone.0002868
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