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General Psychology (PY110). Chapter 3 Sensation and Perception. Windows on the World. Our sensory neurons (receptors) are constantly bombarded with stimuli We understand the world through our senses, our “windows” on the world Our reality, in fact, is dependent upon two processes :
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General Psychology (PY110) Chapter 3 Sensation and Perception
Windows on the World • Our sensory neurons (receptors) are constantly bombarded with stimuli • We understand the world through our senses, our “windows” on the world • Our reality, in fact, is dependent upon two processes: • Sensation: Gathering information • Perception: Interpreting information (a process)
Bottom-up Processing and Top-down Processing • Bottom-up processing is the processing of sensory information as it enters the sensory structures and travels to the brain • Top-down processing is the brain’s use of existing knowledge, beliefs, and expectations to interpret the sensory stimulation • Perception is subjective because of top-down processing • Perceptual set occurs when we interpret an ambiguous stimulus in accordance with our past experiences • A contextual effect occurs when we use the present context of sensory input to determine its meaning
Illusion Vs Hallucination Perception Stimulus Interpretation Response Perception Illusion Stimulus Misinterpretation Response Illusion Misinterpretation can be caused by Hallucination No Stimulus Misinterpretation Response Hallucination
Perceptual Organization Gestalt means “organized whole” • Gestalt psychologists believe that the organized whole is greater than the sum of its individual pieces of sensory information • The figure-and-ground principle states that the brain organizes sensory input into a figure (the center of attention) and a ground (the background)
An Example of Figure-Ground Ambiguity Both purses do the same job… Right? So they should cost about the same… Right?
Gestalt Principles of Organization • Similarity-objects similar are considered a unit • Proximity-because of spacing objects considered a unit • Closure- the tendency to fill in the gap to produce a familiar object
Similarity Does this furniture go together?
Proximity What do you see? Did you interpret the closeness of these two people as evidence of a relationship?
Closure What is this? What about this? Do you see the white triangle?
Perceptual Constancy • Refers to the perceptual stability of • Size – Football player • Shape - Nickel • Brightness - Coal • Color - Coca-Cola • For familiar objects seen at • Varying distances • Different angles • Different lighting conditions
Perceptual Constancy - Color Can this really taste the same as this?
Perceptual Constancy - Size Even though they look like ants from our seats… We know how big they really are
Perceptual Constancy - Shape We know that both of these balls are actually the same shape because our experience tells us how a football is shaped
Visual Illusions In the Ponzo illusion, two horizontal lines are equal in length, but one appears longer than the other • The convergence of the two lines (i.e., linear perspective) outside the horizontal lines normally indicates increasing distance
Visual Illusions In the Müller-Lyer illusion, two vertical line segments are equal in length, but the one with arrow feather endings appears to be longer • The line with arrow feather endings has the appearance of a corner that is receding away from you (the corners where two walls meet in a room), while the line with arrowhead endings has the appearance of a corner that is jutting out toward you (the corners where two sides of a building meet) • Thus, it is our past experience with corners that leads the brain to believe that the line with arrow feather endings is farther away
