Ludimar Hermann first observed the Hermann Grid and characterized it with “spectral gray spots perceived at the intersections of a white grid on a black background,” (Spillmann & Levine, 1971). Baumgartner believed that the effect was due to inhibitory processes in retinal ganglion cells, the neurons that transmit signals from the eye to the brain (Baumgartner 1960). However, Hermann's grid alone provides only a biological explanation of visual processing and therefore, in attempting to fully explain visual processing, we must look for explanations that also include the environment as part of the explanation. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay At the center of an intersection, there is more light in its inhibitory environment than in the receptive field located elsewhere along the same line. More light in the inhibitory environment means there is more lateral inhibition at the intersection. Lateral inhibition disables the spread of action potentials from excited neurons to neighboring neurons in a lateral direction (Yantis & Steven, 2014). This creates a contrast in stimulation that allows for greater sensory perception. An important feature of the Hermann grid is that by staring directly at the intersection, no gray spots will appear but rather they will be seen in peripheral vision. This is explained by the fact that the receptive fields in the central fovea are much smaller than in the rest of the retina and are too small to cover the width of an intersection. In contrast, the Hermann grid provides only a limited explanation for visual processing. Schiller and Tehovnik (2015) cite three main flaws. First, although our receptive fields remain the same size, when the Hermann Grid changes size, the illusion changes as well. Second, the illusory effect can be greatly reduced or even removed completely by tilting or otherwise distorting the grid by as little as 45 degrees. Third, the actual arrangement of retinal ganglion cells and corresponding receptive fields is not as simple as Baumgartner supposed. Dwarf and parasol ganglion cells exist in different ratios throughout the retina, the latter having much larger center-surround receptive fields than the former. This complicated arrangement of excitatory centers and inhibitory surroundings, operating at various distances on the 2-D retinal image, means that localized Baumgartner retinal processes cannot explain the Hermann grid effect (Schiller and Carvey 2005). Therefore, it can be concluded that visual processing cannot be explained by lateral inhibition alone, and therefore there must be alternative explanations. Cognitive explanations suggest that we process visual information through cognitive processes such as attention and retention. The two main cognitive explanations for visual processing include the work of James Gibson and Richard Gregory's bottom-up theory. James Gibson suggests that perception involves innate mechanisms forged by evolution and that no learning is required. This suggests that perception is necessary for survival because without perception the environment would be very dangerous. Our ancestors would have needed perception to escape harmful predators and to know which fruit is poisonous and which is safe to consume, thus suggesting that perception is evolutionary. The starting point of Gibson's theory was that the pattern of light reaching the eye, known as the optical matrix, contains all the visual information necessary for perception. This optical array provides unambiguous information on the.