Introduction to Psychology

Introduction to Psychology

Chapter Three: Sensation and Perception Learning Objectives After completing this unit, you should be able to: 1. Discuss the area of psychophysics and the process in which our sense organs receive and transmit information 2. Discuss the sensory systems including vision, auditory, taste, and smell and their involvement in receiving and transmitting information 3. Discuss how the body perceives touch, pain, body position, and other sensations 4. Discuss how the brain interprets sensory input 5. Discuss what underlies our perceptions of the physical world 3.1 Psychophysics and Thresholds Psychophysics is the area of psychology that addresses the topic of sensation: the levels of intensity at which we can detect stimuli, how sensitive we are to changes in stimulation, and howpsychological factors influence our ability to sense stimuli. According to signal detection theory, our ability to notice a stimulus will vary due to psychological factors including motivation, past experiences, and expectations. In some ways, sensation and perception blend together making it difficult to separate the two. Nevertheless, psychologists do distinguish between them. Sensation is the stimulus detection process by which our sense organs respond to and translate environmental stimuli into nerve impulses that are sent to the brain. Perception is making sense of what our senses tell us. It is the active process of organizing this stimulus input and giving it meaning. The minimum stimulation needed for a given person to detect a given stimulus (an odor, taste, sound, etc.) is called an absolute threshold. It is typically thought of as the intensity necessary for a stimulus to be detected 50 percent of the time that it is presented. The smallest difference a person can detect between two similar stimuli is called the just noticeable difference or the difference threshold. According to Weber’s Law, this threshold increases in proportion to the intensity and magnitude of the stimuli. 3.2 Sensory Adaptation From a survival perspective, it is important to know when some new development requires our attention. Sensory neurons are engineered to respond to a constant stimulus by decreasing their activity, and the diminishing sensitivity to an unchanging stimulus is called sensory adaptation. Sensory adaptation is adaptive, because it frees our senses from the constant and the mundane, allowing them to pick up informative changes in the environment that could be important to our well- being or survival.

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