Here are a couple of extracts and an image from chapter 7 (on vision/perception) of my new book 'Embracing the Wide Sky: A Tour Across the Horizons of the Mind':
"Color is a good way to illustrate the remarkable variety and subjectivity of our perceptions. The range of colors that we see when we look around us, though impressive, is in fact far from exhaustive. Humans are normally able to perceive colors with wavelengths of 400 nanometers (violet) through to 700 nanometers (red), with purples, blues, greens, yellows and oranges in between. Birds, however, can see what we cannot – ultraviolet range colors with shorter wavelengths (between 340 and 400nm). For every color that we see, our feathered friends see many more. "
(From a later section of the chapter:)
"Ambiguous images have long been a staple of optical illusions – images that are designed to demonstrate the vagaries of our perceptions. The ‘open book’ illusion, for example, invented by the German psychologist Ernst Mach, can be seen as either open towards or away from the viewer. Once both perspectives are seen, the viewer’s eye will oscillate between the two representations as our brains try to make sense of what it is seeing..."