PSY101 Ch. 4 Sensation & Perception PDF

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Jason Whetten...

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Perception- the process of organizing and interpreting sensory information so that it makes sense Bottom-up vs. top-down processing ○ Bottom-up- sensory receptors register information about the external environment and send it up to the brain for interpretation (building on input to perceive) ○ Top-down- launched by cognitive processing, begin with some sense of what is happening and apply that framework to incoming information from the world (draws from experience and expectation) ○ Ex: when you listen to a song for the first time, bottom-up processing allows you to get a feel for the tune. Once you know the song well, you can create a perceptual experience in your mind’s ear, by “playing” it in your head- that’s top-down processing Sensory receptors- specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and the brain Synaesthesia- an experience in which one sense (ex: sight) induces an experience in another sense (ex: hearing) ○ a person might “see” music or “taste” a color Phantom limb pain- feeling pain from a missing limb Absolute threshold- minimum amount of stimulus energy that a person can detect Difference threshold (noticeable difference)- the degree of difference that must exist between 2 stimuli before the difference is detected Subliminal perception- the detection of information below the level of conscious awareness Sensory adaptation- a change in the responsiveness of the sensory system based on the average level of surrounding stimulation Opponent-process theory- cells in the visual system respond to red-green and blue-yellow colors; a given cell might be excited by red and inhibited by green, whereas another cell might be excited by yellow and inhibited by blue ○ Explains afterimages (if you stare at red, for instance, your red-green system seems to “tire,” and when you look away, it rebounds and gives you a green afterimage) Contour- a location at which a sudden change of brightness occurs Figure-ground relationship- the principal by which we organize the perceptual field into stimuli that stand out (figure) and those that are left over (background, or ground) Gestalt psychology- a school of thought interested in how people naturally organize their perceptions according to certain patterns ○ Gestalt is german for “configuration” or “form” ○ “The whole is different than the sum of its parts” summarizes the gestalt principle ○ Principles of gestalt: ■ Closure: When we see disconnected or incomplete figures, we fill in the spaces and see them as complete figures

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Proximity: When we see objects that are near each other, they tend to be seen as a unit ■ Similarity: When we see objects that are similar to each other, they tend to be seen as a unit The human retina has approximately 126 million receptor cells. They turn the electromagnetic energy of light into a form of energy that the nervous system can process ○ There are 2 kinds of visual receptor cells: rods and cones ■ Rods and cones differ both in how they respond to light and in their patterns of distribution on the surface of the retina ■ Rods- the receptor cells in the retina that are sensitive to light but not very useful for color vision, night vision ■ Cones- the receptor cells in the retina that allow for color perception, operate best in daylight Depth perception- the ability to perceive objects three dimensionally ○ Does not require both eyes Monocular cues vs. binocular cues ○ Monocular- powerful depth cues available from the image in one eye, either the right or the left ○ Binocular- based on the combination of the images from the left and the right eyes that help determine the depth of objects The disparity, or difference, between the images in the two eyes is the binocular cue the brain uses to determine the depth, or distance, of an object Convergence- a binocular cue to depth and distance In humans, we have neurons that are specialized to detect motion Apparent movement- the perception that a stationary object is moving Perceptual constancy- the recognition that objects are constant and unchanging even though sensory input about them is changing ○ Size constancy is the recognition that an object remains the same size even though the retinal image of the object changes. Experience is important to size perception: No matter how far away you are from your car, you know how large it is ○ Shape constancy is the recognition that an object retains the same shape even though its orientation to you changes. Look around. You probably see objects of various shapes—chairs and tables, for example. If you walk around the room, you will see these objects from different sides and angles. Even though the retinal image of the object changes as you walk, you still perceive the objects as having the same shape ○ Color constancy is the recognition that an object retains the same color even though different amounts of light fall on it. For example, if you are reaching for a green Granny Smith apple, it looks green to you whether you are having it for lunch, in the bright noon sun, or as an evening snack in the pale pink of sunset Photoreception- detection of light, perceived as sight

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Mechanoreception- detection of pressure, vibration, and movement, perceived as touch, hearing, and equilibrium Chemoreception- detection of chemical stimuli, perceived as smell and taste Thalamus- the brain’s relay station Extrasensory perception (ESP)- the ability to read another person’s mind or perceive future events in the absence of concrete sensory input ○ Does not exist Noise interferes with the perception of stimuli Weber’s law- the principle that two stimuli must differ by a constant proportion to be perceived as different...