PSYCH 240 LEC 5 (PATTERN RECOGNITION: BOTTOM-UP)

Bottom-up Processing

• Processing originates in sensory areas + proceeds upwards toward areas responsible for higher cognition

pattern recognition theories

• Template recognition

• Feature

• Structural description

shape constancy

• Despite different orientation, the shape of a butterfly remains the same, helps with pattern recognition

Template Theory Matching

• A break down perceptual + memory representation in pixels

• Match with what you visualized vs what you perceive

  • Block = perceptual rep.

  • Shape = memory rep.

  • Fitting blocks into their particular shapes

• Memory shape rep. in the ventral visual cortex + where we have pattern recognition

Template Theory Problems

• Transformation

  • Issue with orientation need to move to match against memory

  • Different letter fonts

• Obstructed Objects

  • Cannot see whole object doesn’t match with memory rep.

• Visual System Feature Decomposition

  • Scenes into primitive features

Feature theory for Pattern Recognition

• Perceptual rep

  • Set of primitive features

• Memory rep

  • Assume and match same set of features here

• Helps with matching different objects

evidence for features

• Physiology (recordings from neurons)

  • responds well with specific bars of light + location

• Stabilized retinal images

  • eye moves so photoreceptors don’t get tired

• Visual images

  • help with recognizing cues vs. distracters

visual search

• Surrounding Q with circular words make it easier to ID

• Surrounding Z with angular words make it easier to ID

  • Circular + Angular words are distractors

  • Q + Z are the cues

  • Shows how features help with recognize the cues vs the distractors

Pandemonium model

• Computational model for feature theory

• Break down image → primitive feature → feature demons → cognitive demons

  • Feature demons yell based on how much evidence they found their specific feature, cognitive demons listen to the loudest yell to find their letter

caricatures

• Exaggerate features

  • Test give people one image of both normal image + caricature of person

    • People recognized the caricature of person quick that supports feature theory

problems with feature theory

1. Relationship between feature

• dependent on set of features, hard to distinguish

1. Different arrangements of the same features produce diff objects

• hard to distinguish

Structural descriptions

• mental representation stored in memory that describes an object (or concept) by detailing its individual parts and the spatial relationships between those parts.

  • chair is coded as a flat seat surface attached to four vertical legs beneath it and a vertical backrest attached above it

RECOGNITION BY COMPONENTS theory

• Recognize 3D objects by breaking them down into geons

Good at:

• Transformations (rotating non-accidental properties)

• Relationships between features

• Explaining how we make sense of nonsense nonsense objects

geons

• Represent objects in cylinder + cone form

non-accidental properties

• Reliable, no matter what orientation

  • Straight edges

  • Curved edges

  • Parallel

• Some nonaccidental differences between brick and a cylinder

RBC (Matching Process)

1. Use vision to detect elementary features, edges

2. Find non-accidental properties

3. Determine component geons

4. Match to memory

RBC evidence

• Partial or Degraded objects

  • Deleting non-accidental properties = harder to ID images

  • Deleting accidental properties = easier to ID images

• Object complexity

• Unusual orientations

problems with RBC theory

1. Brain evidence?

• None.

2. Context effects

   1. knowledge, beliefs, goals, and expectations

3. Hard with faces