L5 sensation/perception p2

Introduction to Perception

• Teaching experience via online lectures can be novel and challenging.

• Aim: Make class interesting, engaging, and informative.

The Gestalt Principles of Perception

• Gestalt Psychology: Concerned with how we perceive wholes from parts.

• Universal laws of perception allow us to create complete pictures from individual elements.

Laws of Grouping

Law of Proximity

• Objects close together are perceived as a unit.

• Example: Groups of X's and O's seen as pairs (XO) rather than individual letters.

Law of Similarity

• Similar objects are grouped together in perception.

• Example: X's form a line and O's form a line, rather than an alternating pattern.

Law of Continuity

• Lines and smooth curves are perceived as continuous rather than disjointed.

• Example: The brain interprets an 'X' as overlapping straight lines, not as angles.

Law of Closure

• Gaps in figures are filled in by the brain to perceive completeness.

• Example: Dashes perceived as a complete circle or triangles in a given arrangement despite literal absence.

Figure and Ground Perception

• Figure: The object of focus in perception.

• Ground: Background elements that are not the focus but are part of perception.

• Reversible Figures: Perception changes depending on what is seen as figure vs. ground.

• Example: A vase vs. two faces in profile.

Ambiguous Figures

• Examples that shift perception: Young woman vs. old woman, Necker cube.

• Different interpretations based on visual cues and context.

Top-Down Processing

• Perception is influenced by expectations, motivations, and past experiences.

• Example: Image can be read as a 'B' or '13' depending on surrounding context (A, C or 12, 14).

• Expectation shapes perception:

• The gobbledygook text demonstrates how knowledge of language aids interpretation.

Depth Perception

• Ability to perceive three dimensions and distance.

• Two types of cues:

  • Monocular Cues: Require one eye.

  • Binocular Cues: Require both eyes.

Monocular Cues

Interposition (Overlap)

• Closer objects block further objects.

• Example: Red balloon overlapping blue balloon perceived as closer.

Shadowing

• Provides depth information via shadows; shadows indicate distance based on perceived light direction.

Relative Clarity

• Distant objects look hazy due to air impurities and distance.

• Issue for city dwellers hiking in clearer landscapes.

Texture Gradients

• Objects further away appear denser and less detailed.

• Example: Sunflowers appear more sparse when close, but packed together when far away.

Motion Parallax

• The perception of movement of nearby objects differs from far-away objects when in motion.

• Example: Trees appear fast moving compared to the slowly moving moon.

Linear Perspective

• Parallel lines appear to converge in the distance.

• Example: Railroad tracks that seem to touch at a distance illustrate depth perception.

Relative Size

• Objects cast larger images on the retina when closer.

• Perception adjusts for scale based on distance cues.

Ponzo Illusion

• Background context influences perceived relative size.

• Example: Two equal lines on railway tracks appear different sizes due to linear perspective cues.

Binocular Cues

Convergence

• Eyes' inward movement indicates object distance.

• Closer objects require greater eye convergence.

Retinal Disparity

• Different images cast on each retina due to eye distance provide depth cues.

• Closer objects yield greater disparities between images seen by each eye.

Fusion

• Combining of distinct retinal images into one perception.

• Relationship between disparity and distance perception.

• Example: Using a paper tube to perceive depth indicates the brain's attempt to fuse images.

Application in Media

• Hollywood employs retinal disparity to enhance 3D effects in films.

• Different colors in 3D glasses manipulate depth perception using retinal disparity.