Perception

· What is?

· The way brain interprets sensation.

· The same sensation may produce different perception.

Several factors that affect perception.

· Sensitivity

· Feature detection

· Perceptual organization

· Depth perception

· Perceptual constancy

Two types of sensitivity

· Absolute threshold – absolute minimum

· Difference threshold – Minimum difference needed to determine between two sensations.

· These would vary depending on conditions.

Absolute threshold

· Changes because of noise.

· E.g., noisy condition – difficult to hear the signal.

Difference threshold

· Changes because of current experience

· Weber’s Law

§ Glasses on the tray

Feature detection

· We first take object apart.

· Visual cortex – cells that respond to specific orientation.

· Experience is very important.

· E.g.,

§ A cat raised in “vertical” environment.

§ Unable to see horizontal orientation.

Perceptual Organization

· Then, we organize.

· Gestalt psychologists

§ Hw do we organize sensation?

§ Innate ways – Laws of perceptions

Laws of perception

· Figure – ground

§ Separate figure and ground

· Proximity

§ Closer objects

· Similarity

§ Similar objects

Depth Perception

· We also create 3-d images

· Two cues.

§ binocular cues

§ nocualar cues

Binocular cues

· Binocular disparity

§ Two eyes receive two different images.

· Convergence

§ How much two eyes have to be crossed.

Monocular cues

· Relative size

· Interposition (one over lapping the other makes one look bigger)

· Texture gradient (closer you get the more detail can be seen)

· Relative height (object farthest away appears taller)

· Relative motion (when driving a car bushes move fast water tower in background moves slow)

· Linear Perspective (airplane lines appear to converge but actually run parallel)

Constancy

Innate or Learned (born with ability to do this or it is learned)

· Os perceptual ability innate or learned?

· Nativists – innate

· Empiricists – learned.

· Perceptual set – learned.

·