Karl Ewald Konstantin Hering (5 August 1834 – 26 January 1918) was a German physiologist who did much research in color vision, binocular perception, eye movements, and hyperacuity.

Hering seems to have applied for studying under his direction but was rejected,[citation needed] which might have contributed to his animosity towards Hermann von Helmholtz, Müller's protégé.

Although there is no evidence that Hering ever studied under their direction, in his later years he proudly acknowledged himself a "student of Fechner".

There he became involved in fierce arguments between nationalistic Czechs who wanted the university taught in the language of the land, and a minority of German professors.

In his late years, Hering returned to Germany, where he became professor at the university of Leipzig in 1895, aged 61.

Despite identical results, Hering's derivation was far more modern and elegant, using recently developed projective geometry.

In his famous 1899 treatise "On the Limits of Visual Acuity"[6] he summarized empirical data published 1863 by Alfred Wilhelm Volkmann[10][11] and Ernst Anton Wülfing 1892[12] who found that there are visual tasks in which spatial resolution goes well below the size of receptor cells in the central retina.

[13] In an explanatory model, Hering superimposed a Vernier acuity stimulus – a disalignment among two line segments – onto an idealized receptor array.

He developed the Hering's law of equal innervation to describe the conjugacy of eye movements in animals.

Hering disagreed with the leading theory developed primarily by Thomas Young, James Clerk Maxwell and Hermann von Helmholtz.

This was interpreted by Helmholtz as proof that humans perceive colors through three types of receptors, while white and black would reflect the amount of light.

The conundrum was resolved by the discovery of color-opponent ganglion cells in the retina and lateral geniculate nucleus.

Hering first suggested the idea of organic memory in an 1870 lecture for the Imperial Academy of Science in Vienna.

Hering took influence from the idea of inheritance of acquired characteristics and suggested that memories could be passed on through generations by germ cells.

Helmholtz also came from a higher social class and was always considered a prodigy, whereas Hering had to go through a harder time in his early career.