Object Recognition

PSYCH 333 Exam 2

What is the main problem of object recognition?

Turning point-by-point retinal signals into meaningful objects

What must the brain decide?

What belongs to the same object vs different objects

What do photoreceptors do?

Detect light like pixels

What do midget ganglion cells do?

High resolution + edge detection

What do early cortical neurons detect?

Edges, lines, orientation, size

Why are these important?

They are basic features used to build objects

What is perceptual organization?

Organizing raw input into meaningful structure

First step in perceptual organization?

Detect edges

What comes after edge detection?

Represent uniform regions

What is figure-ground segregation?

Separating object from background

What is grouping?

Combining similar regions into objects

What is filling in?

Completing missing parts (occlusion)

What is object recognition?

Matching perception to stored memory

Key question it answers?

“What is this object?”

What is bottom-up processing?

Local features → global perception

Example of bottom-up?

Fraser spiral illusion

What is top-down processing?

Expectations influence perception

Example of top-down?

Necker cube

Does perception use only one type of processing?

No, both bottom-up and top-down

Who founded Gestalt psychology?

Koffka, Köhler, Wertheimer

Core idea of Gestalt psychology?

The whole ≠ sum of parts

What does Gestalt emphasize?

Perception is organized, not built piece-by-piece

What is the Law of Prägnanz?

We perceive things in the simplest way

Another name for it?

Law of good figure

Proximity?

Close items are grouped

Similarity?

Similar items are grouped

Common motion (fate)?

Moving together = grouped

Symmetry & parallelism?

Symmetrical/parallel = grouped

Good continuation?

Smooth lines seen as one object

Connectedness?

Physically connected = grouped

Common region?

Same boundary = grouped

Synchrony?

Same timing = grouped

Meaningfulness (familiarity)?

Meaningful patterns are grouped

What is figure-ground organization?

Separating object (figure) from background

What is border ownership?

Determining which side “owns” an edge

Example of figure-ground illusion?

Face-vase illusion

What are regularities?

Assumptions the brain uses about the world

Example of border ownership rule?

Closer objects own borders

Why are regularities important?

Help brain make accurate guesses

What is occlusion?

Objects are partially hidden, not broken

Key assumption?

One object is in front of another

What is unconscious inference?

Perception = unconscious guesses

What is the likelihood principle?

Brain chooses most likely interpretation

Modern version?

Bayesian perception

What features build objects?

Edges, angles, curves, orientation

Evidence for feature processing?

Specialized neurons (face cells, object cells)

What is local → global processing?

Bottom-up

What is global → local processing?

Top-down

Do these processes interact?

Yes, constantly

What do illusions show?

Perception is interpretation, not reality

Why are illusions useful?

Reveal how the brain constructs perception