Introduction to Psychology

Sensation and Perception

Prof. Jan Lauwereyns

jan@sls.kyushu-u.ac.jp

What do sensory systems do?• Information about the world• Each system responds in a specific way

to a stimulus• They use specialized cells, peripheral

receptors• Transduce the energy

– Represent stimulus into brain signals

• Different stimulus energies(Platypus)

 

• Different stimulus energies(Platypus)

 

Electroreception throughsensitive bill

• Different stimulus qualities(Bees, dolphins)

 Separate groups of neurons Constantly updating

Rubin vase• Interaction between   Ascending, stimulus-driven

Descending, goal-oriented(Focusing attention)

 • This interplay shows:

Difference between sensation and perception

While making eye movements, our eyes detect similar information on the same portion of the retina, and so they conclude that these things must havebeen moving along, but this can’t be…

Structure of the eye

Goodale & Milner:

Dorsal, spatial = “Vision for Action”

Ventral, object = “Vision for Perception”

The "Where" (Dorsal) Stream: Spatial Processing

The "Where" (Dorsal) Stream: Spatial Processing

Motion agnosia: inability to perceive motion

How do Iput this thing in that slot?

e.g., Unable to see whether cars are moving or standing still

Damage to area MT (Medial Temporal):Module in the dorsal stream

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The “What" (Ventral) Stream: Object Recognition

The “What" (Ventral) Stream: Object Recognition

Prosopagnosia:Face blindness

•Feature Integration (simple to complex)

•Recognition by Components, RBC (Biederman)

– Visual ‘alphabet’

– Infinite combinations

–Viewpoint-independent

(a) A familiar object; (b) the same object seen from a viewpoint that obscures most of its geons and therefore makes it harder to recognize.

Can you read this?

• The template-matching approach– E.g., bar codes– But requires infinite number, each template

has to be learned as new, not robust against visual degradation

– Matching to exemplars based on similarity – Viewpoint-dependent

Perceptual Organisation

• Gestalt laws:

– Simplicity (Closure)– Similarity– Good continuation– Proximity– Common fate– Familiarity

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Familiarity

Influence of context

• Objects are not presented in isolation

• Effects of visual context– E.g., 3D illusion

• Effects of semantic context– E.g., Effects of knowledge, expectation

Difficulties formachine vision:

Maximal interpretationfrom minimal information