Extraversion and cortical arousal

1. Extraversion is Eysenck's dimension covering sociability, impulsiveness and sensation-seeking.
2. He explained it through cortical arousal, meaning how much activity is going on in the thinking layer of the brain.
3. An extravert's cortex sits below the level that feels comfortable, so the brain is chronically under-aroused.
4. Three structures do the work here: dopamine reward systems, the reticular activating system and the cerebral cortex.
5. Learn what each one does on its own as well as how the three work together.

What each structure does

1. Dopamine reward systems: the pathways that release dopamine when something rewarding happens.
   1. In an extravert these pathways respond strongly to novelty and risk, so a thrill produces a large release of dopamine.
   2. That release makes the experience feel pleasurable, so whatever produced it gets repeated.
2. Reticular activating system: the network of nerves in the brainstem that filters how much incoming stimulation is passed up to the cortex.
   1. In an extravert it filters more of that stimulation out, so less arrives and the cortex stays under-aroused.
   2. Gray (1970) found the reticular activating system is more active in introverts, whose cortex is therefore already well stimulated.
3. Cerebral cortex: the brain's wrinkled outer layer, handling thinking, perception, language and voluntary movement.
   1. Arousal is registered in this layer, so a low level here feels like boredom.
   2. Wright et al. (2006) found an inverse correlation between the thickness of the right inferior frontal cortex and extraversion scores.

How the three work together

1. Stimulation from the outside world reaches the brainstem first.
2. The reticular activating system decides how much of it is passed up, and in an extravert it passes up less.
3. So the cerebral cortex never reaches the level that extravert is comfortable at.
4. Low cortical arousal feels like boredom, restlessness and a flat mood.
5. To lift it, the extravert goes looking for loud, fast or risky stimulation.
6. When they find it, the dopamine reward system fires and the experience feels good as well as stimulating.
7. That reward reinforces the search, so sensation-seeking settles into a habit.

Extraversion and offending

1. Sensation-seeking pushes an extravert towards bold, risky acts, and a minority of those acts are crimes.
2. Shoplifting, joyriding and vandalism all raise arousal fast, which suits an under-aroused brain.
3. The dopamine reward that follows makes the risk feel worth taking a second time.
4. Low cortical arousal also makes an extravert harder to condition, because a telling-off produces too little arousal for the lesson to stick.
5. Extraversion explains only one part of the picture, and Eysenck's criminal personality needs high neuroticism and high psychoticism alongside it.

Turning this into marks

1. When all three structures are asked for, give each a different job: filtering for the reticular activating system, registering arousal for the cortex and reward for the dopamine pathways, rather than the same point about stimulation three times.
2. Name the structure and where it sits, such as the reticular activating system in the brainstem, because writing that the brain filters information does not secure the knowledge mark.
3. The mark most often lost is bringing in the overactive dopamine system here, when that claim belongs to psychoticism and extraversion uses the dopamine reward pathways instead.