S1 Humans

Topic

Humans are, first and foremost, a primarily visual species: nearly a third of the cerebral cortex processes visual information—the same type of information defined by another model in this set. Consequently, human foveal resolution reaches the diffraction limit established by that other model, constrained by both physical limits and the spacing of the photoreceptor mosaic within the fovea itself. Although the total capacity of the human retina is comparable to that of the optic nerve described in the other model, it undergoes massive compression to a much lower information rate within the realm of conscious perception. The fact that the retina’s capacity is so high means that the necessary final compression—viewed in the context of conscious perception—is even more severe.

The human auditory system covers the same audible range as the other model in this set, with a frequency resolution equivalent to thousands of independent frequency channels within the cochlea. Furthermore, this system achieves a considerable dynamic range through the active amplification provided by outer hair cells—a process similar in spirit to the frequency selectivity of a finely tuned Pacinian corpuscle (as described in the other model)—combined with additional mechanical compression of the basilar membrane. Because the human auditory system divides this frequency range into a greater number of independent channels within the cochlea, it is able to discriminate more precisely between two sound frequencies that are very close to one another. The sense of touch in humans involves four types of mechanoreceptors—as established by another model in this set regarding glabrous (hairless) skin: Meissner's corpuscles, sensitive to relatively low-frequency vibration; Pacinian corpuscles, sensitive to much higher frequencies; Merkel discs, sensitive to fine texture; and Ruffini endings, sensitive to skin stretching. Consequently, the density of these four mechanoreceptor types is highest at the fingertips and lowest on the back, following the same relationship between sensor density and resolution established by another model in this set. Thus, a higher density of mechanoreceptors in a specific skin region results in greater tactile resolution for that region.

Although inferior to that of most other mammals, the human sense of smell involves hundreds of functional olfactory receptor types, enabling the discrimination of a vast array of distinct odorant mixtures through the same receptor-ligand binding kinetics described by another model in this set regarding chemoreception. In contrast, the sense of taste is organized around just five basic tastes, mediated by numerous taste buds distributed across the tongue. The presence of a greater number of functional olfactory receptor types allows humans—based on those same receptor-ligand binding kinetics—to discriminate between an even wider variety of distinct odorant mixtures. Consequently, this model—characterized by its compressed visual capacity and the four sensory channels through which it initially engages—causes the human being's information processing speed to drop sharply as data moves from the sensory periphery to final conscious awareness; each successive processing level compresses and selects from the information available at the preceding stage, adhering to the same information-gain parameters established by another model in this set regarding active environmental exploration. Ultimately, this compression hierarchy reflects a principle of efficient coding inherent to the human being: only information truly relevant to action ultimately reaches that individual's final conscious awareness. The fact that a specific processing level compresses the available information more intensely ensures that the data finally reaching the human's consciousness is even more selective and relevant to their actions.

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