The human brain reacts to the current state of the human body by secreting some molecules. In this regard, the human brain utilizes the input from organs, as a computer does with sensors, in order to detect and reveal issues about the body-budget, which shall be explained below. This process managing the needs of the human body to survive(body-budget), getting feedback from the human brain, is known as interoception – of course, is not a unique ability for only humans among the other living beings.
“Interoception is your brain’s representation of all sensations from your internal organs and tissues, the hormones in your blood, and your immune system. Think about what’s happening within your body right this second. Your insides are in motion. Your heart sends blood rushing through your veins and arteries. Your lungs fill and empty. Your stomach digest food. This interoceptive activity produces the spectrum of basic feeling from pleasant to unpleasant, from calm to jittery, and even completely neutral.(1)” As you can see, interoception makes you feel calm and pleasant while you are eating carbohydrates although you have not been feeling hungry. In other words, it is a different approach to explain the feeling of delicacy when eating a chocolate bar after dinner. And, which is why valence and arousal occur because of the poignant effects of interoception to our bodies.
For further comprehension, I will give the definitions of valence and arousal as follows. “Affect is the general sense of feeling that you experience throughout each day. It is not emotion but a much simpler feeling with two features. The first is how pleasant and unpleasant you feel, which scientists call valence. The pleasantness of the sun on your skin, the deliciousness of your favorite food, and the discomfort of a stomachache or a pinch are all examples of affective valence. The second feature of affect is how calm or agitated you feel, which is called arousal. The energized feeling of anticipating good news, the jittery feeling after drinking too much coffee, the fatigue after a long run, and the weariness from lack of sleep are examples of high and low arousal. Anytime you have an intuition that an investment is risky or profitable, or a gut feeling that someone is trustworthy or an a**hole, that’s also affect. Even a completely neutral feeling is affect.(2)”
(1) Barrett, Lisa Feldman. "The Origin of Feeling." How Emotions Are Made: The Secret Life of The Brain. London: Macmillian, 2017. 56. Print.
(2) Barrett, Lisa Feldman. "The Origin of Feeling." How Emotions Are Made: The Secret Life of The Brain. London: Macmillian, 2017. 72. Print.
Figure - 66.1 https://www.researchgate.net/figure/Two-dimensional-valence-arousal-space_fig1_304124018