1. General Psychology (PY110) Chapter 3 Sensation and Perception

2. 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)

3. Stimulus – Sensation – Perception Anything that can be received by a receptor Stimulus Awareness of a stimulus A simple mental process Sensation Sensation + Interpretation + Response A complex mental process Perception

4. Examples of Misperception

8. 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

9. Perceptual Organization and Top-down Processing

10. A Context Effect on Perception

11. Illusion Vs Hallucination StimulusInterpretationResponse Perception StimulusMisinterpretationResponse Illusion No StimulusMisinterpretationResponse Hallucination Perception Illusion Hallucination Misinterpretation can be caused by

12. 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)

13. An Example of Figure-Ground Ambiguity

14. Both purses do the same job… Right? So they should cost about the same… Right?

15. 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

16. Similarity Does this furniture go together?

17. Proximity What do you see? Did you interpret the closeness of these two people as evidence of a relationship?

18. Closure Do you see the white triangle? What is this? What about this?

19. An Example of an Organizational Perceptual Ambiguity

22. Examples of Misperception

24. 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

25. Perceptual Constancy - Color Can this really taste the same as this?

26. Perceptual Constancy - Size Even though they look like ants from our seats… We know how big they really are

27. 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

28. Examples of Misperception

33. 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

34. 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

35. Examples of a Visual Illusion

36. Summary of Perception Detects Senses Select Brain Elects based on experience Mind