PSY 324 - Chapter 6

What is Realism?

Everything is actually real, not just our senses

What is Positivism?

The world is created by our senses (Hallucinations)

What are the three principles to Euclidean Geometry?

1. Parallel lines remain parallel as they are extended into space

2. Objects maintain their size and shape as they move into space

3. Internal angles of triangles always add up to 180 degrees

Why do our eyes not adhere to Euclidean geometry?

Our eyes do not operate under these principles because our eyes are curved

What is Binocular Disparity and what does it allow us to perceive?

The differences between the two retinal images which allows for Stereopsis (perception of three-dimensionally of the world)

• At least two (multiple inputs)

• Perception of the 3rd dimension which is depth

• Not fully available with one eye

What are monocular cues?

Cues that provide information about depth even when only viewed through a single eye

What is Occlusion?

The simplest cue we can use to perceive depth with one eye

• One object partially covers another or an object that is really far away (behind)

• Problem is that it only tells you that something is behind another but not how far behind it is - Nonmetrical depth cue

What is Relative Height?

Objects at different distances will form an image on different parts of the retina

• Close = lower in the retinal field

• Far = Higher in the retinal field

What is Relative Size?

Comparison of the size of objects without knowing the actual size of either one

• Assumption: Larger items are closer, smaller items are farther away

• Change in depth not a change in size

What is Texture Gradient

Items of the same size form smaller, closed spaces as they get farther away

• Closer objects have more defined texture, and father objects appear less sharp and texture information is lost

What is Familiar Size?

When you know about the typical size of an object, you can guess how far it is by how large/small it appears

• Often occurs in conjunction with relative size

What is Aerial Perspective?

Light is scattered by the atmosphere… therefore, when something is farther away, we look through more atmosphere

• Blue is more likely to get scattered first which is why we get the blue tint

  • Gives bluish tint

  • Fainter, less distinct

What is Linear Perspective?

Parallel lines appear to converge as they extend into the distance

What is Vanishing Point?

The apparent point at which the lines converge in the distance

What is Motion Parallax?

Objects closer to the observer appear to move faster across visual field than those that are farther away

Accommodation

Process by which the eye changes focus for objects at various depths

• Lens bends and gets “fatter” when objects are close

Convergence

Eyes move inward to focus on close objects - eyes cross

Divergence

Eyes move outward to focus on far objects

Corresponding Points

Points on the retina of each eye have a place when the two images would overlap if they were superimposed on each other

• There will be no disparity - this results in double vision

• If they do not fall on corresponding points, there will be a disparity (double vision)

• Objects that are on corresponding points have ZERO binocular disparity

• Objects that are not on corresponding points will have binocular diversity (Diplopia - Double vision)

Horoptor

Imaginary surface along which objects will form images on corresponding points (no disparity)

• Any objects placed on or near the horopter will form images with zero binocular disparity (seen as a single object)

• Objects significantly distant from the horopter will result in diplopia

Crossed Disparity

Perceptual images are displaced to the left in the right eye and to the right in the left eye

Uncrossed Disparity

Perceptual images are displaced to the left in the left eye and to the right in the right eye

• Occurs when objects are behind the horopter

• Going in the same direction anywhere outside the horopter

Correspondence Problem

Having different images in each eye that we must determine which part of the image in the left eye aligns with the image in the right

What is the solution to the correspondence problem?

1. Uniqueness constraint: Each feature in the world is only represented ONCE in each retinal field

2. Continuity Constraint: Except at the edges of objects, neighboring points lie at similar distances from the observer

What is the Bayesian Approach?

Based on knowledge of the condition in the world and the appearance of the current stimulus, we “calculate” the probability of each possible event

What is Strabismus?

Misalignment of the eye in which a single object will appear in the fovea of one eye and outside of the fovea in another eye

What are the two types of strabismus?

Esotropia: One eye deviates inward

Exotropia: One eye deviates outward (lazy eye)

What is the difference if strabismus occurs in a person from birth vs adulthood

If strabismus occurs at a young age, the individual’s brain learns to suppress the image of the unwanted object