It was known long before chronobiology that the human brain can be divided functionally into three layers, laid down one on top of the other over the course of evolution. The oldest is the archeocortex, sometimes called the reptile brain: it runs breathing, heartbeat, self-defence, the instincts and the unconditional reflexes. Above it sits the paleocortex, the old cortex, where emotion meets the endocrine system and where our adaptive and cooperative reactions are formed. The youngest layer, the neocortex, stores everything we learn in a lifetime and governs conscious thought and acquired behaviour.
The founder of the method, Professor Artur V. Zhaskov, noticed that these three layers correspond to the three biological rhythms already described in biorhythm research: a physical wave of 23 days, an emotional wave of 28, and an intellectual wave of 33. His hypothesis was that the three rhythms and the three layers of the brain change together, and that a person's date of birth fixes the starting point of all three. The combination of the three waves repeats only every 21,252 days, roughly 58 years, which is why two people rarely share a profile.
The three layers also form a hierarchy. In the method's own words: the intellect governs the emotions, and the emotions govern the temperament. Or, put differently, information directs energy, and energy directs the body. This is why a profile is read from the bottom up, temperament first, and why real change has to happen at the level where a pattern actually lives.
Each layer is read through two properties, one for each hemisphere, which gives the six indicators that make up a profile. Those six are the subject of the next piece.