Perception and Gestalt Psychology (Video Notes)

Key concepts from the lecture notes on perception, gestalt principles, depth cues, constancies, and common visual illusions.

Gestalt psychology

A school of psychology that emphasizes perceiving organized wholes (the whole) rather than just the sum of parts.

Figure-ground relationship

The perceptual distinction between the main object (figure) and its background (ground); can be ambiguous.

Law of Pragnanz (Law of Simplicity)

We perceive ambiguous stimuli in the simplest, most stable form possible.

Law of Closure

We tend to perceive complete figures even if parts are missing, filling in gaps mentally.

Law of Good Continuation

We perceive lines and patterns as continuing smoothly rather than abruptly.

Law of Proximity

Objects that are close together are grouped together in perception.

Monocular depth cues

Depth cues accessible with one eye; include texture gradient, linear perspective, interposition, relative size, and motion parallax.

Texture gradient

Texture details become coarser with distance, helping judge depth.

Linear perspective

Parallel lines appear to converge as they recede, signaling depth.

Interposition (overlap)

One object partially covering another is interpreted as closer to the observer.

Motion parallax

As you move, nearer objects appear to move faster than distant ones, aiding depth perception.

Binocular cues

Depth cues that require both eyes; include convergence and binocular disparity.

Convergence

The inward turning of the eyes to focus on a nearby object.

Binocular disparity

Slight differences between the two eyes’ images; the brain fuses them into a single perception.

Perceptual constancies

Objects are perceived as constant in size, shape, and color despite changes in viewing conditions.

Size constancy

Perceiving an object's size as constant even when the image size on the retina changes.

Shape constancy

Perceiving an object's shape as constant despite changes in angle or perspective.

Color constancy

Perceiving colors as relatively stable under varying lighting.

Perceptual illusions

Misperceptions where the brain’s interpretation differs from physical reality.

Moon illusion

The Moon looks larger near the horizon than overhead due to contextual depth cues.

Müller-Lyer illusion

A line appears longer or shorter depending on the orientation of arrowheads at its ends.

Pareidolia / face perception

Seeing faces in inanimate objects; the brain has specialized mechanisms for face detection.

Perceptual set

A readiness to perceive things in a particular way based on expectations.

Top-down processing

Perception guided by prior knowledge, expectations, and context.

Ambiguous figures / figure-ground reversals

Images that can be interpreted in more than one way, with perception shifting between interpretations.