Perception depends on our sense organs that have a different range of "sensitivity" from other species. Our eyes are designed as the eyes of a land dwelling, omnivore, predator. We see differently from other many other species. Some people perceive color differently from most people. Those who are color blind are often said to have a color vision deficiency but those with red-green color blindness can have an advantage over those with normal color vision.

Example of an Ishihara color test plate. The numeral "74" should be clearly visible to viewers with normal color vision. Viewers with dichromacy or anomalous trichromacy may read it as "21", and viewers with achromatopsia may not see numbers.

Some studies conclude that color blind individuals are better at penetrating certain color camouflages; this may be an evolutionary explanation for the surprisingly high frequency of congenital red–green color blindness. So are we to say that the sea is blue (on some days) if this is the consensus but not a universal perception. In what other ways is our knowledge dependent on the range and nature of our sensory equipment (our eyes, ears, nose, tongue and the brain that "wires" it all together)?

What do we make of something like Synesthesia?


noun Physiology & Psychology
The production of a sense impression relating to one sense or part of the body by stimulation of another sense or part of the body.

Daniel Tammet has linguistic, numerical and visual synesthesia — meaning that his perception of words, numbers and colors are woven together into a new way of perceiving and understanding the world. The author of "Born on a Blue Day," Tammet shares his art and his passion for languages in this glimpse into his beautiful mind.- TED talks

Does Daniel Tammet's experience with synesthesia support or contradict the theory of "common sense realism" ?(TOK text p.87). Explain. 2-300 words

The two boys each have a different kind of synesthesia... the one on the floor is smelling records and saying what color they smell like (so he perceives smells as colors), and the one with the headphones is 'listening' to the different foods (he perceives taste as sound). The things coming out of the speakers shows how sound can be perceived as different colors, shapes or textures. What other types of synesthesia can you identify?

Dr. Sacks on Synesthesia

Dr. Oliver Sacks on synethesia

Are you a synesthete? Maybe a little? Find out here and here

For connections to the Arts and perhaps our evolutionary origins Read: A Natural History of the Senses