Our Senses

 

The Institute for Personality and Ability Testing has certified Robert Fettgather as a Stress Management Trainer, and Medical Hypnosis Seminars of the Los Gatos Institute has certified him in Clinical Hypnotherapy.  At Santa Clara University, Graduate Department of Education and Counseling Psychology, Robert Fettgather's studies included Health Education and Behavioral Medicine.

Sensation is the process by which sensory organs in the eyes, ears, nose, mouth, skin, and other tissues receive and detect stimuli. When sensory information is detected by a sensory receptor, then sensation has occurred.

Perception focuses on the organization and interpretation of these stimuli within the human brain. These two work closely together to allow us to experience the world as coherent and meaningful. Of course, the Escher-like print above is one example of visual stimuli that challenges our ability to form a coherent perception. Cloud gazing invites our own projections.

Sensation allows us to receive information from the world around us. According to your text: "Studying sensation means studying human beings, who are complex and variable. Not everyone is born with the same collection of stimulus-detecting equipment. Some individuals have eyes that see "20/20"; while others have worn glasses since they were young children. There is even variation within a given individual".  Yes, human variability does figure into our study of sensation. Let's start with an uncommon experience of sensation. Synesthesia is a rare and unusual condition in which an individual experiences more than one sensation related to a sole stimulus. For example, consider the person who can hear and see... a sound.

For many of us, vision seems to be the most essential of the senses. The retina is quite tiny, the size of a quarter. It contains the sensory receptor neurons that transform incoming light waves in to an electrical-chemical signal that the nervous system can comprehend. Each eye has two types of sensory receptors, rods and cones. Approximately 70 percent of the sensory receptors located in your eyes are rods. Rods perceive the brightness of light and send messages about the levels of black, white, as well as shades of gray. With the exception of the "blind spot", rods occupy the entire retina. To discover why the spot is blind see below. Rods are quite light sensitive, and produce images with low sharpness or acuity. Our ability for the eyes to make adjustments to darkness, as in a dark room, and eventually see objects is mediated by the rods in our eyes. That is referred to as dark adaptation.