Human Cognitive Processes: psyc 345

Ch. 3: Perception

Takashi Yamauchi© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)

Homework & Questions

Q1: How do we perceive?– If you are going to develop a theoretical model

of perception, how does it look like?– Describe your processing model of perception.

Q2: How does the brain become tuned to respond best to things likely to appear in the environment?

Visual illusion

• Let’s take a look at visual illusions and check how your model can explain these illusions. – Ponzo illusion– Muller-Lyer illusion– Ames room

• http://www.youtube.com/watch?v=Ttd0YjXF0no

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Fig. 3-6, p. 50

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The figure represents “some thing.”

The contours belong to the figure rather than to the ground.

Which one is the figure and which one is the ground?

Symmetric items tend to be seen as a figure.

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(A)

(B)

(A)

(B)

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Is your model consistent with these visual illusions?

• How does your model explain these illusions?

• What’s wrong with your models?

• Why do we have these illusions?

• Demonstration– Ames room

• http://www.youtube.com/watch?v=Ttd0YjXF0no

Some examples

• Tired

• Old

• Sick

• Dark

• Slow

• Heavy

• Hospital

• ugly

• death

• Beautiful

• Young

• Fresh

• Fast

• Energy

• Juicy

• Clean

• cheerful

• Vigorous

• Experience influences perception a great deal.

• We need a top-down process as well as a bottom-up process.

• Direct perception theories– Bottom-up processing – Perception comes from stimuli in the

environment– Parts are identified and put together, and then

recognition occurs• Constructive perception theories

– Top-down processing– People actively construct perceptions using

information based on expectations

Bottom-up and top-

down processes

Fig. 3-4, p. 59

Perceptual Organization and Gestalt Psychology

• “Gestalt” means “whole.”

• Organizational principles:– Similarity– Proximity– Continuity

Law of similarity

Similar things are put together

Items with similar colors are put together

Law of proximity

• Things that are close to each other are put together.

Law of good continuity

We tend to put things together when they show nice continuity.

Why do we need top-down knowledge?

• Because the bottom-up process is inherently ambiguous.

Why computers have trouble perceiving objects?

• The bottom-up process is difficult. solving the inverse projection problem

• Computers do not have a large amount of background knowledge as we have.

• Humans have an incredible accumulation of knowledge.

• Use knowledge to solve perception problems

Fig. 5-4, p. 96

Neurons and the Environment[Q2] How does the brain become tuned to respond

best to things likely to appear in the environment?

– Some neurons respond best to things that occur regularly in the environment

– Neurons become tuned to respond best to what we commonly experience

– Neurons that respond to similar visual information (e.g., shape, motion, color, faces, etc) are grouped together.

Two visual pathways (where & what systems)

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Two visual pathways (where / how & what system)

Patient D. F had bilateral damage to the ventral path.

Carbon monoxide poisoning at age 35.

• Video clip: NPR• NPR: Blind man sees with subconscious eye

(12/23/08); Interview and video record– This can be used as evidence for the “how” pathway.

– http://www.npr.org/templates/story/story.php?storyId=98590831

– A blind man who damaged the occipital lobe can still navigate and walk without bumping into objects.

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Object discrimination task

Landmark discrimination task

The monkey had to select the correct object to get the food reward

The monkey had to select the food well close to the cylinder.

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Object discrimination task

Landmark discrimination task

Can’t do the object discrimination task but can do the landmark discrimination task

Can’t do the landmark discrimination task but can do the object discrimination task

Modularity: structures for faces, places, and bodies

Figure 4.18 (a) Monkey brain showing location of the inferotemporal cortex (IT) in the lower part of the temporal lobe. (b) Human brain showing location of the fusiform face area (FFA) in the fusiform gyrus, which is located under the temporal lobe.

Prosopagnosia

• Episode from

• “The man who mistook his wife for a hat”

• By Oliver Sacks– Oliver Sacks interview– http://www.youtube.com/watch?

v=zQPI0BIkOkE

Copies of the black (A) and

the white (B) vertical contour.

Copies of the black (A) and

the white (B) diagonal contour.

• DVD: the mind eye (Ch.6 – Ch. 8) (10min)– Agnosia (Ch. 8)– Propasognosia (Ch. 6 - 7)

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Mirror neurons

Mirror neurons• Mirror neurons respond to a particular

“kind” of action (e.g., grasping) AND observing someone doing the action.

The activity of a particular neuron in the premotor area of a monkey.

The activity of a particular neuron in the premotor area of a monkey.

(a) This neuron responded when the monkey watched the experimenter picking up the peanut.

(b) This neuron also responded when the monkey actually picked up the peanut.

(c) This neuron did not respond when the monkey watched the experimenter pick up the food with pliers.

Mirror neurons

• Respond not only when you are doing a particular action.

• But also when you watch someone doing it.

• This neuron gives you a general characteristic of an action.

What are mirror neurons for?• Facilitate learning by imitation.

– Language development– Skill learning

• Social interaction– Empathy (understanding others or what others

think)– Connecting with others

• Autism may be caused by the deficiency in mirror neurons

• Video clip from NOVA (PBS)– 15 min

– http://www.pbs.org/wgbh/nova/sciencenow/3204/01.html