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Chapter 5

Chapter 5- Sensation and Perception p. 170-211

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Psychology 1000

Chapter Five Notes Sensation and Perception p.170-211 Key term: Synesthesia Mean quick literally mixing of the senses, colours or tastes as touch sensations that have different shapes Sensation 1. Stimulus is received by sensory receptors 2. Receptors translate stimulus properties into nerve impulse (transduction) 3. Feature detectors analyze stimulus features 4. Stimulus features are reconstructed into neural representation 5. Neural representation is compared with previously stored information in brain 6. Matching process results in recognition of stimuli Weather the stimulus is light, sound waves, a chemical molecule, or pressure, you sensory receptors must translate this information into the only language your sensory receptors understand, the language of nerve impulses. Perceptions and sensations are very hard to separate, The stimulation that we receive through our sense organs is instantaneously organized and transformed into the experience that we refer to as perceptions Sensation: Is the stimulus- detection process by which our sense organs respond to and translate environmental stimuli into nerve impulses that are sent to our brain Perception: Making sense of what our sense tell us- is the active process of organizing this stimulus input and giving it meaning Sensory Process You brain cannot understand light waves, sound waves, or the other forms of energy that make up the language of the environment Contact with the outer world only is possible because certain neurons have developed into specialized sensory receptors that can transform these energy forms into the code language of nerve impulses 5 Senses: vision, audition (hearing), touch, gustation (taste), and olfaction (smell), but there are actually much more than these We are designed to take away from the environment the information that we need to survive Psychophysics: studies relations between the physical characteristics of stimuli and sensory capabilities, considered with two types of sensitivity 1) absolute limits of sensitivity (Softest sound? weakest salt solution we can detect) 2) Second has to do with difference between stimuli (how much difference in tones must there people before we are able to tell that they are not identical Stimulus detection: The absolute threshold Absolute threshold: as the lowest intensity at which a stimulus can be detected correctly 50 percent of the time, thus the lower the absolute threshold the greater the sensitivity Many of our senses are surprisingly sensitive Table 5.1 on page 172, some approximate absolute thresholds for various sense Signal Detection theory Psychologist concluded that the concept of a fixed absolute threshold is inaccurate because there is no single point on the intensity scale that separates non- detection from detection of a stimulus Detection criterion: a standard of how certain they must be that a stimulus is present before they will say that they detect it Signal Detection Theory:is concerned with the factors that influence sensory judgments The matrix shows four possible outcomes for this theory (p.p 172) Signal detection research shows us that perception is, in part a decision Subliminal stimulus: Is one that is so weak or brief that, although it is received by the senses, it cannot be perceived consciously- thus the stimulus is well below the absolute threshold It is argued that subliminal cues can bias what we perceive at a conscious lever al may alter our conscious experience of those stimuli The difference threshold Is defined as the smallest difference between two stimuli that people can perceive 50 percent of the time, it is sometimes called the just noticeable difference (jnd) Webers law: states that the difference in threshold is directly proportional to the magnitude of the stimulus with which the comparison is being made, and can be expressed in webers fraction. The smaller the fraction, the greater sensitivity to differences. Sensory Adaption Sensory systems are finely tuned to changes in stimulation 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 Adaptation occurs in every sensory modalities Although sensory adaptation may reduce our overall sensitivity, it is adaptive because it frees our senses from the constant and the mundane to pick up information changes in the environment The Sensory systems Vision The normal stimulus for vision is electromagnetic energy, or light waves, which are measured in nanometers (nm). Humans can only perceive tiny portions the electromagnetic spectrum includes x-rays, television, and radio signal Our vision is sensitive only to wavelengths extending about 700 nm (red) down to 400 nm (blue- violet) You can memorize the order of the spectrum from higher to lower wavelengths with the name ROY G. BIV: red, orange, yellow, green, blue, indigo, violet. It goes from highest Infrared to ultraviolet The Human eye Light waves enter the eye through the cornea (a transparent protective structure at the front of the eye Behind the cornea is the pupil (an adjustable opening that can
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