Intro to Sensation of Perception

PSYCH 333 Exam 1

What is sensation?

Transforming physical stimuli into neural signals (action potentials)

Where does sensation occur?

At sensory receptors

What is perception?

Interpreting neural signals to create conscious experience

Key difference between sensation vs perception?

Sensation = input; Perception = interpretation

What type of stimulus is sound?

Air pressure

What type of stimulus is vision?

Electromagnetic radiation

What type of stimulus is smell/taste?

Molecules

What type of stimulus is touch?

Mechanical force

What is the correct order of sensory processing?

Distal → Proximal → Neural signals → Brain → Perception

What is a distal stimulus?

The actual object in the world

What is a proximal stimulus?

Energy that hits sensory receptors

Example of distal vs proximal stimulus?

Tiger (distal) → light entering eye (proximal)

Why is sensation & perception important?

• Helps technology (interfaces, devices)

• Helps treat sensory disorders

• Explains biology and brain function

• Perception seems simple but is complex

What does it mean that receptors “selectively sample”?

We detect only a small range of stimuli

Visible light range?

~400–700 nm

Human hearing range?

~20–20,000 Hz

Why don’t we perceive everything we sense?

• Attention filters information

• Unconscious processing

What does the brain add during perception?

• Depth (stereo vision)

• Color

• Illusions

Key idea?

Perception ≠ physical reality

What does it mean that perception is an inference?

The brain makes a “best guess” about reality

Is perception veridical?

No (not perfectly accurate)

What influences perception?

• Experience

• Expectations

• Context

• Evolution

What does evolution prioritize in perception?

Useful and efficient representations, not accuracy

Distal stimulus definition?

Real object in environment

Proximal stimulus definition?

Physical energy contacting receptors

Brain’s goal?

Infer distal stimulus from proximal input

What do illusions demonstrate?

Perception ≠ reality

Why are illusions important?

Show the brain actively constructs perception

Examples of illusions?

• Illusory motion

• Hermann grid

• Neon color spreading

• Illusory contours

What is the “light-from-above” assumption?

The brain assumes light comes from above

Why is “light from above” heuristic important?

Helps interpret shape (bumps vs dents)

Is color in the object?

No — it’s constructed by the brain

What exists physically instead of color?

Wavelengths of light

What does the brain create?

Continuous hues + basic unitary hues

What is perceptual constancy?

Perception stays stable despite changing input

Color constancy?

Same color despite lighting changes

Size constancy?

Same size despite distance

What are context effects?

Perception depends on surroundings

Key idea of context effects?

Same stimulus can be perceived differently depending on context