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Table 2 Examples of receptors for a human observer

From: Spatial and temporal resolution of geographic information: an observation-based theory

Sense Receptors, Number & Size References
Hearing eardrum (or tympanic membrane) of the ear; there is one eardrum per ear; the surface area of an eardrum is about 85 mm2 [9395]
Sight photoreceptors of the retina; photoreceptors are about 125 million in each human eye; their diameter varies roughly between 2.5 µm and 10 µm [93, 9597]
Smell olfactory cilia of the olfactory neuron in the nose; there are about five million olfactory neurons in each nose, each neuron has 8-20 cilia; cilia have a length between 30 and 200 µm [95, 98, 99]
Taste taste buds of the tongue; a human has between 5,000 and 10,000 taste buds; taste stimuli interact with taste buds at a small 2-10 µm region called the taste pore [93, 95, 100, 101]
Touch touch receptors of the skin; there are about 17,000 touch receptors in the human hand; the mean spatial receptive field of touch receptors of type FAI is about 12.6 mm2 [70, 93, 95]
  1. The table illustrates that information about the type of receptors involved in an observation process, their number and their size is available from research on neuroscience and can be used to compute the spatial receptive field of the observer (and thereby estimate the spatial resolution of human observations, based on physical properties of the observers)