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

Approaches to Approaches to Perception - Perception -

Indirect Indirect PerceptionPerceptionPS2009/10 Lecture 4PS2009/10 Lecture 4

Sources of InformationSources of Information Sensory InputSensory Input

Past KnowledgePast Knowledge

QuestionsQuestions How do they influence Perception?How do they influence Perception?

What is the relative importance of each What is the relative importance of each source?source?

ApproachesApproaches Indirect or Constructive ApproachIndirect or Constructive Approach

Direct or Ecological ApproachDirect or Ecological Approach

Indirect ApproachIndirect Approach

Bruner (1957)Bruner (1957) Neisser (1967)Neisser (1967) Gregory (1972)Gregory (1972)

“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)

Perception is an active processPerception is an active process

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

Ambiguous FiguresAmbiguous Figures

Figure-Ground ReversalsFigure-Ground Reversals

The Necker cubeThe Necker cube

Muller-Lyre IllusionMuller-Lyre Illusion

Ponzo IllusionPonzo Illusion

Neisser (1969)Neisser (1969)

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

Indirect PerceptionIndirect Perception

Perceivers Perceivers SEESEE retinal images retinal images

Retinal images are snapshots of the Retinal images are snapshots of the environmentenvironment

Perceptual stimuli are discrete Perceptual stimuli are discrete samplessamples

Perception of MotionPerception of Motion

Motion needs to be inferred from the Motion needs to be inferred from the snapshots of the environmentsnapshots of the environment

Representational MomentumRepresentational Momentum

Evaluation of Perception Evaluation of Perception as an indirect processas an indirect process

Perception is fast AND accuratePerception is fast AND accurate Are illusions a good way of testing Are illusions a good way of testing

the perceptual system?the perceptual system? What hypotheses should be formed?What hypotheses should be formed? How does information get into the How does information get into the

system in the first place?system in the first place?

Ames RoomAmes Room

Figure Ground Figure Ground Distinctions (Von Distinctions (Von

Sneden, 1960)Sneden, 1960)