Writing about findings on the brain and Introversion/Extraversion was a walk in the park, relative to the other temperament findings. E/I behaviors are fairly visible and both temperament science and public opinion seem to agree on most of the qualities that are involved. From formal research studies to the ever popular Myers-Briggs Type Indicator, the names and descriptions are markedly similar.
This is much less true for other temperament areas. The MBTI and the Keirsey model yield four sets of preferences out of eight possible choices, making this a four factor model. On the other hand, the most widely used and accepted model among psychologists is the Five Factor Model or Big Five. This includes Extraversion, Agreeableness, Conscientiousness, Openness and Neuroticism, with the opposite pole being implied in each case (for example, the opposite of Neuroticism would be Emotional Stability). All except Neuroticism have considerable overlap with the MBTI, but are not identical. For example, here, Openness includes aethetic or artistic sensibility and is also thought to measure intelligence to some degree. The nearest MBTI scale would be Intuition, in the Sensing/Intuition pair. There is no implication that art sensitivity plays a role in Intuition, and if there is a relationship with intelligence it is less obvious.
Looking at a few other scales, there is a longstanding model developed by the British psychologist Hans Eysenck that is a three factor model with Extraversion, Neuroticism, and Psychoticism, and their polar opposites. Psychoticism in its original form seems to have been mainly a measure of Anti-social personality, but the term suggested that it would include other psychotic disorders such as schizophrenia. Criticism of this scale has let to changes and to the development of other two and three factor scales, which are mostly used in research. Last but not least, there is one very interesting model that suggests that a single factor stands above all the other factors. This is Effortful Control–the brainchild of developmental psychologist Mary Rothbart.
These models and their interesting theoretical relationships to the brain bring very positive new ideas to the field of temperament research, but also make it hard to pull together a simple picture of brain and temperament. Psychoticism as Anti-social personality is a very productive field in brain research with important findings that go right down to single genes. But–I had to find limits here, and that area is probably not what we think of as common or normal temperament. So, I am going to limit recent findings to those for the MBTI and the Big Five.
While multiple researchers have reported on EEG brain activity differences in Extraversion/Introversion, I know of only one study that has looked at all four of the MBTI factors. If there is anything newer on this I would love to hear from any of you about this. Anyhow, this 2005 study confirmed the usual findings for Extraversion/Introversion and went on to look at the other factors–Intuition vs. Sensing, Feeling vs Thinking, and Perceiving vs. Judging. Intuition is simply creativity and imagination. Sensing is an orientation to the here and now, practical problem solving, and an orientation toward performance, whether sports, art or other activities. Perceiving and Judging are, very briefly, flexibility and openness to what happens, versus organization, planning and structure. Feeling and Thinking refer to the use of these styles in making decisions–whether values and emotions are foremost or logical analysis.
They found EEG differences in Intuition/Sensing that were certainly interesting. Sensors showed significantly greater amounts of Theta waves (common in deep relaxation and sleep), while Intutives showed greater amounts of Beta1 a wave reflecting moderate amounts of activity. The simplest explanation for this is that in this setting (a quiet, non-stimulating environment) the Sensors found little to attend to, while Intuitives probably did more internal processing of their own thoughts. The main Thinking/Feeling differences came from more EEG activity in Feelers throughout Theta, Alpha and Beta than was true for Thinkers. I suppose one possibility might be that the Feelers were more emotionally engaged in the whole experimental process, but no explanation was given.
Finally, with respect to Perceivers versus Judgers, Judgers produced more EEG activity over all, in all of the waves measured, as compared to Perceivers. If this finding holds up you might imagine that Judgers were busy thinking of their To-do and Already-Done lists and Perceivers, like Sensors, were less mentally active in a restricted environment. These ideas are fun, but given a single study they need much confirmation.
A 2010 study, looked at the Big Five factors (these are sometimes called OCEAN for Openness, Conscientiousness, Agreeableness, Extraversion and Neuroticism), and brain structure–specifically changes in the volume of different areas of the brain. The working assumption is that greater volume equals a larger or more important role for a given area.. They used an MRI technique to measure volume, and hypothesized in advance the greater volume that they would expect to correlate with each of the Big Five factors based on theoretical models and other brain research. No meaningful volume relationship was found for Openness. For the rest, with the single exception of one odd finding for Agreeableness, actual area volume and predicted volume were in good agreement. This is not proof positive, but again it is supportive of brain and temperament coordination.
Other studies have looked at one temperament factor at a time, and most often at only a portion of that factor. For example, a study of “individual differences in negative affect” defined this affect as “irritability, anxiety and anger”. This would relate well to the Big Five’s neuroticism, but is probably not identical with it. This study used PET techniques to measure regional blood flow, and found that a central area of the prefrontal cortex (very roughly behind the bridge of your nose) is significantly more active in persons who report more negative affect. We might assume the same for those who score high on neuroticism, but can’t be sure of it from this.
Yet another study that looks at one aspect of the Big Five Agreeableness factor and the MBTI Feeling factor, is focused on empathy and the role of the hormone, Oxytocin. Oxytocin became famous some years ago as a “bonding” hormone in the prairie vole. Voles are small, mouse-like creatures. The prarie vole was found to be unusually monagamous, with the male not only remaining faithful, but often participating in raising the offspring (of which there are a lot, with 5-10 litters per year). Meanwhile, a cousin, the meadow vole, is highly promiscuous. A critical difference between them is in levels of oxytocin–high in the prairie vole and low in the meadow vole. From this oxytocin has come to be seen as a bonding hormone in humans also, particularly in the mother-infant bond. Research has shown that other chemicals are also involved, but oxytocin remains of great interest. This current study looked at empathy by asking each participant to look at a series of videos of persons who were discussing emotional events, and then rate the persons on how positive or negative they thought the person was feeling at a given point. Meanwhile each participant had taken a paper and pencil test of their normal empathy level. Half of the participants received oxytocin intranasally, and half received a placebo. They returned a few weeks later and did the task again, with the oxytocin/placebo doses reversed. Their accuracy in predicting the target person’s feelings was the major measure. Those with poor natural empathy scores improved considerably in the oxytocin condition, and scored poorly without it. Those already high in natural empathy did not change much in the oxytocin condition. The bottom line was that the poor natural empathizers and good natural empathizers performed equally well when both had oxytocin. Insofar as empathy is a part of Agreeableness and Feeling, this is yet more support of a brain and temperament link.
There are many hundreds of studies of brain structure and chemistry like these, that relate in some way to innate temperament. For the present most are looking at specific fragments of brain function and fragments of individual temperament factors. It may be a long while before it all comes together, but keep watching. It is on its way!
Gram, P. C., Dunn, B. R. & Ellis, D. (2005). Relationship between EEG and Psychological Type. Journal of Psychological Type, 5, 33-45.
DeYoung, C.G. Hirsh, J. B. ….Gray, J. (2010). Testing predictions from personality Neurosciences: Brain structure and the Big Five. Psychological Science 8, 820-828.
Kemp, A. H. (2011). The role of oxytoxin in human affect: A novel hypothesis. Current Directions in Psychological Science, 20(4), 222-231.
Zald, D. H., Mattson, D. L. & Pardo, J. V. (2002). Brain activity in ventromedial prefrontal cortex correlates with individual differences in negative affect. Proceedings of the National Academy of Sciences, 99(4) 2450-2454.