Chapter 3: Sensation, Perception and Human Potential (10/30) -- Psychology

Chapter 3: Sensation, Perception and Human Potential Vision Every man takes the limits of his own field of vision for the limits of the world. Arthur Schopenhauer, Studies in Pessimism (1851). Whether adapting to the rainforest or a modern city, we rely heavily on vision to survive and enjoy our surroundings. From the time we wake up in the morning to the time we go to bed at night, we almost constantly process and respond to visual information. We move about our surroundings, locating needed substances and objects, constantly assessing achievement of our goals. We fashion and use tools tailored to the demands of our unique environmental niches. Examples include blowpipes in the rain forest and laptops in our schools. No matter where they reside, humans engage in creative arts. Examples include playing flutes and fashioning necklaces in the rainforest; and playing flutes and fashioning necklaces in cities. The more some things change, the more they stay the same! We gaze upon and pay close attention to the appearance of others as we interpret facial expressions and body language in our interpersonal interactions. As expressed by Schopenhauer, our interpretation of our world and life is based upon what we see. For most of our history on earth, humans experienced daily changes in the amount of light based upon the position of the sun. Only in the light do we experience the beauty of color. Seeing in the dark is a very different and more challenging experience. We will review how our eyes detect and process reflected light to enable color perception, and adapt to different levels of illumination. Transduction refers to the process through which physical stimulation is converted into neurological action potential and transmitted from receptors to higher brain regions for further processing. Figure 3.3 shows the major parts of the eye involved in the transduction process converting light into electronic signals transmitted to the brain. Light reflected from objects enters and undergoes initial focusing as it passes through the transparent cornea. Depending upon darkness or brightness, the iris dilates or closes, controlling the amount of light reaching the lens. The lens changes shape depending upon distance of the object, completing focusing. The remaining focused beam of light reaches photoreceptors lining the surface of the retina. Most of the light reaches the center of the retina, with the fovea being the small focal point with the greatest concentration of photoreceptors. Signals from the photoreceptors travel along nerve fibers to the optic nerve at the back of the eye. From there the signals are transmitted to the occipital lobe of the cerebral cortex. Figure 3.3 The Human Eye Color Vision Can you imagine the world without color? Figures 3.4and 3.5 demonstrate not only the beauty which would be missing, but also the amount of potentially adaptive information. It is far easier to identify similarities and differences or look for a particular fe