Of course, a human can have a need to look admirably at cherry blossoms when this need is formed, but it is difficult to study. On the other side, the needs of eating, reproducing, and security are a lot easier to study. You can model these needs on animals, and of course, these needs are more studied. We can see that biological needs are genetically integrated in the brain. The needs are initial programs that are “installed” in our brain computer, and without their realization, we can’t function fully. It works so that when a human can meet a need, he or she experiences positive emotions, and when he or she can't meet his or her needs, he or she experiences negative emotions. Humans as well as animals build their lives in the way that makes it possible to experience positive emotions more often and negative emotions less often.

The need is like a lighthouse that leads us through our life, and the emotions that we experience in the dependence of meeting or not meeting the needs are fundamental for learning.When you make something right or you get what you want, you experience positive emotions. In the background of these emotions, the brain remembers, “Aha, in order to eat, I need to do this and that.” When you don't meet your needs, you experience negative emotions, and the brain remembers, “So, you shouldn't do it.” There is a chain: need → emotion → learning. This chain always functions in our nervous system, and it is a main component of mental activity.

Physiologists and psychologists have had to do with needs for a very long time. What neurobiologists call "needs" now correlates pretty exactly with what Ivan Pavlov called unconditional reflex. The term of Freud, “the unconscious,” is also pretty similar to a need.

The really serious and accurate scientific knowledge about the needs has appeared only in the second half of the XX century. The process of studying the needs has been going on. In the XXI century, new technologies have been developed that allow us to see how nerve cells work and how certain chemicals influence different needs.