The basic human emotion is a feeling of either positive or negative, though there is an older animalistic feeling, aggression and fear.
We can categorize these as two dimensions, one for positive and aggression and the other for negative and fear, while the aggression and fear are actually located in the cerebellum, the more primitive part of the brain. On the other hand, the positive and negative emotions are likely created in the cerebral cortex which is the area more human than animal. Although, the dopamine and serotonin might affect to compose those feelings, which suggests their feelings are results of more complex brain activity including the hypothalamus.
The reason why I cannot conclude the brain area where the positive and negative come from is that I still cannot contain a generation of these feelings. However, their influence can be controlled by the strong-mindedness; i.e. you cannot believe the perception under the positive feeling influence and you can ignore when negative.
The aggression and fear are harder to be controlled by whatever mind. The strong-mindedness is a function of the frontal lobe to separate the reason from the emotion. The positive and negative is more linked to the reason or the rational decision making, while these feelings are kind of instinct, quite supportive but ignorable.
On the other hand, the aggression and fear are the alternative to the reason, it is kind of purely emotional instinct, which can occasionally overwhelm the rationality. They are basically suppressed by the reason and the frontal lobe, hence their explosion almost should not appear as the dangerous behavior in the ordinary state.
The very-low frequency electromagnetic wave can control the aggression and fear as well to become more explosive. When their explosions overwhelm the reason control, they are transformed to the actual behavior. If that is the case for the aggression, it is transformed to the brutal aggressiveness to the surroundings including the murder. The key is a balance between the emotion and the reason.
It also implies the explosive behavior can be created by lowering the reason control. If the frontal lobe is malfunctioned, you cannot stop the brutal action with a slight ignition of the aggression which is usually prevented internally.
This phenomenon holds true to the fear which emerges in the cerebellum, and then, controlled by the frontal lobe. The fear is usually suppressed but if the operator ignites your fear more than you can control, you will act irregularly under its control to leave the reason away.
This aggression and fear are the same as emotions of the fight or flight. In the primitive world, the human ancestor should take a fight or flight reacted to a change of the situation. The aggression was exploded to its change for the fight and the fear was for the flight. If the brain control is shifted from the frontal lobe to the cerebellum with the aggression, it removes the restriction on the muscle to move effectively. The fear also makes the flight easier, though its excessiveness makes the human frozen.
These functions are fundamentally different from the positive and negative. Some animals should hold these positive and negative emotion, but not all of them. When the brain function is limited, these are not facilitated in their brains. On the other hand, the aggression and fear are shared by more living creatures as one of the basic brain functions.
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