When you look at the colour red — do you see the same thing as your neighbour? Logic suggests yes: we have the same eyes. But science says: not necessarily. Different variants of opsin genes in the retina, different neural signal-processing circuits, different experience — all of this means that 'red' in your brain may be somewhat different from 'red' in your neighbour's. We will never know for certain. But we are beginning to understand the mechanisms behind these differences.
Perception is not a passive recording of reality. It is an active construction by the brain from sensory data, memory, expectations, and genetically defined parameters of sensory system function. Your sense organs are individually calibrated filters.
Most people are trichromats: their retinas contain three types of cone cells sensitive to red, green, and blue light. Colour-blind men are dichromats: only two types function. And a small number of women — estimated at 2–12% — may have four types of cone cells. They are called tetrachromats.
Tetrachromacy arises from a mutation in one of the opsin genes on the X chromosome, creating a fourth receptor type. Since women have two X chromosomes, they can carry one 'standard' and one 'mutant' variant — and both can be functional. In men with one X chromosome, this is impossible: there is only one variant or the other.
What this means in practice: Artist Concetta Antico is a confirmed tetrachromat. When she looks at tree leaves, she does not simply see 'green' — she perceives dozens of shades: golden, purple, bluish veins invisible to most people. Her paintings are an attempt to convey on canvas what others are literally unable to perceive. A tetrachromat does not 'see more' in a quantitative sense — they distinguish more differences within the visible spectrum.
Absolute (or perfect) pitch is the ability to identify the pitch of a sound without an external reference. Only about 1 in 10,000 people in Western populations possesses it. Among professional musicians — roughly 1 in 1,500. And in approximately 1 in 5 speakers of tonal languages (Mandarin, Vietnamese).
This points to an interaction between genetics and early linguistic experience: a genetic predisposition most likely exists, but it is realised only under the right conditions during a sensitive developmental period.
The concept of the 'Highly Sensitive Person' (HSP) was introduced by psychologist Elaine Aron in the 1990s. According to her research, approximately 15–20% of people process sensory information more deeply: they respond more acutely to noise, light, tactile stimuli, and emotional intensity.
The neurobiological basis of HSP is heightened activity in the insular cortex and amygdala during sensory stimulus processing, documented in several fMRI studies. The genetic basis is associated with variants of the SERT gene (serotonin transporter, SLC6A4) and the cannabinoid receptor gene CNR1.
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