Perception is how animals take energy from the environment and convert it into a representation that the mind can use.

Examples:

• Pattern of light on the retina -> Image in the mind

• Pattern of sound waves (air compression) on the eardrum -> understanding a spoken sentence

• Pattern of pressure on the skin -> Pain, pleasure, itch

1. How do we organize the information we take in?

For example, how do we determine that the dashes in a dashed line make up one line?

2. Related to (1), how do we equate perceptions from different modalities over time?

For example, you link the sound of a car driving down the street with the visual image of that car into a unitary sensation of "car driving down the street."

3. How do we equate different perceptions?

For example, you can identify your car when you see it from any angle, or even from an angle you’ve never seen it from before.

4. How do perceptions influence actions? What mechanisms allow us to perform very different actions based on very similar perceptions?

For example, what tells us when how hard we need to press on the brakes when we see the brake lights of the car in front of us? What tells us whether we should hit the brakes hard or swerve?

Two major questions:

1. How do we decide what is where?


i.e., In depth, in space, etc.

Are there differences between the modalities?

2. How do we decide what things go together?

Depth Perception:

Two major types of perceptual depth cues:

1. MONocular (one-eyed) cues

• Occlusion
• Texture gradients
• Relative size
• Linear perspective
• Aerial perspective
• Distance from the horizon
• Motion parallax — objects that are closer

2. BINocular (two-eyed) cues

• Binocular convergence
• Binocular disparity

Vision:

• Size constancy: An object that we are familiar with always seems to be the same size, regardless of how far away it is.

• Shape constancy: An object always seems to be the same shape, regardless of the angle we are viewing it from.

• What other perceptual constancies do you think there might be?

Gestalt Rules of perception:

• Proximity
• Similarity
• Good continuation
• Closure
• Symmetry

Cross-modal groupings: Ventriloquism effect

When you watch a movie, does the sound of the actor’s voice seem to come from the direction of the actor’s mouth, or from the direction of the speakers?

Other interactions of perceptual modalities:

McGurk effect: Listening to someone say "ba-ba" while watching them articulate "ga-ga" leads to hearing "da-da"

Botvinick & Cohen: Rubber hand illusion

Driver & Spence: cross-modal attentional map in parietal lobe