Contrast effect

The oldest reference to simultaneous contrast in the scientific literature is by the hand of the 11th century physicist Ibn al-Haytham who describes spots of paint on a white background appearing almost black and conversely paler than their true colour on black:[1] He also describes that a leaf green paint may appear clearer and younger on dark blue and darker and older on yellow:[1] Johann Wolfgang von Goethe writes in 1810 that a grey image on a black background appears much brighter than the same on white.

[8][9][10] There has been some debate over the degree to which simultaneous contrast is a physiological process caused by the connections of neurons in the visual cortex, or whether it is a psychological effect.

The most likely evolutionary rationale for this effect is that it enhances edges in the visual field, thus facilitating the recognition of shapes and objects.

In the early 20th century, Wilhelm Wundt identified contrast as a fundamental principle of perception, and since then the effect has been confirmed in many different areas.

For example,[18] African countries have increasingly looked to China and India as opposed to the US, the EU and the World Bank because these Asian states have highlighted their lack of "interference" and "conditionality" in exchange for foreign aid and FDI.