1. Approaches to Perception - Indirect Perception PS2009/10 Lecture 4

2. Sources of Information Sensory Input Sensory Input Past Knowledge Past Knowledge

3. Questions How do they influence Perception? How do they influence Perception? What is the relative importance of each source? What is the relative importance of each source?

4. Approaches Indirect or Constructive Approach Indirect or Constructive Approach Direct or Ecological Approach Direct or Ecological Approach

5. Indirect Approach Bruner (1957) Bruner (1957) Neisser (1967) Neisser (1967) Gregory (1972) Gregory (1972)

6. Much as the information channels of instruments, such as radio telescopes, transmit signals which are processed according to various assumptions to give useful data, so neural signals are processed to give data for perception. To understand perception, the signal codes and the stored knowledge or assumptions use for deriving these hypotheses need to be discovered Gregory (1980)

7. Perception is an active process Perception is an active process Perception is not directly given by the stimulus input, but is the end product of the interaction between the stimulus, expectations, hypotheses, and the knowledge that the perceiver brings to the situation. Perception is not directly given by the stimulus input, but is the end product of the interaction between the stimulus, expectations, hypotheses, and the knowledge that the perceiver brings to the situation.

8. Ambiguous Figures

9. Figure-Ground Reversals

10. The Necker cube

11. Muller-Lyre Illusion

13. Ponzo Illusion

15. Neisser (1969) Visual cognition, then deals with the process by which a perceived, remembered, and thought about world is brought into being from as unpromising a beginning as the retinal patterns.

16. Indirect Perception Perceivers SEE retinal images Perceivers SEE retinal images Retinal images are snapshots of the environment Retinal images are snapshots of the environment Perceptual stimuli are discrete samples Perceptual stimuli are discrete samples

17. Perception of Motion Motion needs to be inferred from the snapshots of the environment Motion needs to be inferred from the snapshots of the environment Representational Momentum Representational Momentum

18. Evaluation of Perception as an indirect process Perception is fast AND accurate Perception is fast AND accurate Are illusions a good way of testing the perceptual system? Are illusions a good way of testing the perceptual system? What hypotheses should be formed? What hypotheses should be formed? How does information get into the system in the first place? How does information get into the system in the first place?

19. Ames Room

20. Figure Ground Distinctions (Von Sneden, 1960)