chapter 3

1: Chapter 3 Sensation and Perception

3: Absolute threshold: the smallest intensity of a stimulus that must be present for the senses to detect it. Difference threshold: the smallest level of added or reduced stimulation required to sense that a change in stimulation has occurred. Adaptation: An adjustment in sensory capacity after prolonged exposure to unchanging stimuli.

4: Seeing Light rays enter the eye by passing through the cornea. Light then passes through the pupil. Directly behind the pupil is the lens which assists in bending the light rays. The lens focuses light by changing its own thickness, a process called accommodation ) The ability of the lens to change its shape and bend light rays so that the objects are in focus.) The light rays are then focused on the retina and are upside down and reversed. There are two kinds of light sensitive receptor cells in the retina. Rods: Photoreceptors in the retina that allow sight even in dim light, but that cannot discriminate colors. Cones: Photoreceptors in the retina that are less light-sensitive than rods, but that can distinguish colors. Colorblindness: cones normally contain 3 kinds of chemicals, each of which responds best to a particular wavelength of light. If a person does not have all 3 chemicals he/she is considered to be color blind.

5: Hearing Pinna-The crumpled part of the outer ear that collects the sound waves and funnels the sound waves into the auditory canal leading to the eardrum. The more intense the sound the more the eardrum vibrates. These vibrations are transferred to the middle ear. Sound waves set up vibrations in the middle eard which are amplified by three tiny bones names for their shapes (hammer, anvil, and stirrup). Sound waves then enter the inner ear reaching the cochlea. The inner ear is the portion of the ear that changes sound waves into a form in which they can be transmitted to the brain. Sound waves then run through the fluid filled tube consisting of the basilar membrane in turn bending hair cells on the membrane and sending a neural message tot the brain. Damage to these hair cells can result in deafness. (loud sounds, amplified music such as rock music or using headphones with the sound turned up to high)

6: The Chemical Senses: Taste and Smell Smell The sense of smell is activated when the molecules of a substance enter the nasal passages and meet olfactory cells. The responses of the separate olfactory cells are transmitted to the brain where they are combined into recognition of a particular smell. Pinching your nose prevents you from smelling odors, and taping a nasal dilator strip over the bridge of the nose intensifies odors.

7: Taste The sense of taste involves receptor cells that respond to four basic qualities: sweet, sour, salty, and bitter. The receptor cells for taste are located in roughly 10,000 taste buds distributed across the tongue and other parts of the mouth and throat. The taste buds wear out and are replaced every 10 days or so.

8: Sensing Your Body What is the largest organ in your body? Somatic Senses: Senses including touch, temperature, pain, and kinesthesia that are spread throughout the body rather than located in a specific organ. Gate Control Theory: A theory suggesting the presence of a �gate� in the spinal cord that either permits or blocks the passage of pain impulses to the brain. When receptors are activated because of an injury or problem with part of the body, a �gate� to the brain is opened allowing us to feel pain. The gate can be shut in 2 ways. 1. other impulses can overwhelm the nerve pathways relating to pain. Reasons why we can relieve pain by rubbing the skin around a wound or why scratching relieves itching. 2. Psychological Factors: depending on an individuals current emotions, interpretation of events, and previous experience, the brain can close a gate by sending a message down the spinal cord to an injured area, producing a reduction in or relief from pain.

9: Perception Gestalt Laws of Organization: A series of principles that describe how we organize bits and pieces of information into meaningful wholes. Closure: group elements to from enclosed or complete figures rather than open ones. Proximity: perceiving elements that are closer together as grouped together. Similar: we perceive elements that are similar to each other as grouped together. Simplicity: when we observe a pattern, we perceive it in the most basic, straightforward manner that we can. We opt for the simpler interpretation.

10: Recognizing the Perceptual World Top-Down Processing: Perception that is guided by higher-level knowledge, experience, expectations, and motivations. Bottom-Up Processing: Perception that consists of the progression of recognizing and processing information from individual components of a stimuli and moving to the perception of the whole.

11: Perceptual Constancy: phenomenon in which physical objects are perceived to have constant shape, color, and size, despite changes in their appearance or in the physical environment. Ex. An airplane does not change shape or size as it approaches, flies overhead and disappears. Depth Perception: The ability to view the world in 3 dimensions and to perceive distance. Is due largely to the fact that we have 2 eyes.