The Optic Array Concept

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Questions and Answers

According to J. J. Gibson, what is the optic array?

The collection of light rays interacting with objects in the viewer's world. (correct)

The apparent motion of objects as an observer moves through a scene.

The changing angular position of objects in a perspective image.

The visual information gathered by the center of the optic flow field.

In the context of motion perception, how is optic flow defined?

The apparent motion of objects unrelated to the observer's movement.

TThe changing angular position of points in a perspective image that we experience as we move through the world (correct)

The motion of objects in a scene as observed by an external observer.

The changing angular position of objects in a still image.

When an observer moves within a scene, what does the term 'optic flow' refer to?

The apparent motion of objects in the visual field as an observer moves through or within a scene. (correct)

The relative motion between objects in the scene.

The motion of objects in the scene as observed by an external observer.

The constant speed of objects in the visual field.

Which of the following best describes the center of our vision in the context of motion perception?

The center of optic flow. Signup and view all the answers

What kind of information does changing the location of objects relative to the center of the optic flow field provide to an observer?

Information about the observer's direction of movement. Signup and view all the answers

How does optic flow result from the relative motion between the observer and elements in the visual scene?

Objects closer to the observer move faster in the opposite direction of the observer's movement. Signup and view all the answers

Which of the following best describes the 'focus of expansion' in motion perception?

A point in a visual scene where all motion appears to converge or radiate from when the observer is in motion. Signup and view all the answers

What is the primary function of the 'focus of expansion' (FOE) in motion perception?

It helps the observer determine their heading and direction of motion. Signup and view all the answers

How does the 'focus of expansion' contribute to navigation and direction perception?

It indicates forward motion when moving towards the center of the visual field and backward motion when moving away from the center. Signup and view all the answers

Which of the following best describes biological motion perception?

The perception and recognition of movements and actions of living beings based on their motion. Signup and view all the answers

What characterizes biological motion perception?

Recognizing complex motion patterns without relying on fine-grained details. Signup and view all the answers

What does the statement 'we are sophisticated at using motion to represent characteristics of what we're looking at in a coarse sense' mean?

We can interpret characteristics based on motion without needing fine details. Signup and view all the answers

Which of the following can be recognized from the pattern of movement in biological motion?

c. Gender, animal species, and mood. Signup and view all the answers

Which brain area is associated with the processing of biological motion?

b. Superior temporal sulcus. Signup and view all the answers

What is Time to Contact (TTC) in the context of motion perception?

b. The estimated time until a moving object reaches a certain point of collision or proximity with another object. Signup and view all the answers

Which of the following is the correct method for calculating Time to Contact (TTC)?

c. By dividing the distance to the collision point by the relative velocity between the moving object and the reference point. Signup and view all the answers

What does Tau (τ) represent in the context of time-to-contact estimation?

c. A dimensionless ratio of the size of a retinal image of an object to the rate of change of the size of the retinal image. Signup and view all the answers

How is the tau ratio used by the brain?

d. To estimate the time it will take for a moving object to reach another object or observer. Signup and view all the answers

What is the main challenge faced by the visual system in motion perception?

Distinguishing between motion on the retina due to eye movements and motion on the retina due to moving objects. Signup and view all the answers

How is 'retinal movement' defined in the context of motion perception?

Objects moving on the retina. Signup and view all the answers

Which of the following conditions is necessary for an object to be perceived as moving?

a. When there is retinal movement and no eye movement, and vice versa. Signup and view all the answers

When is an object perceived as stationary?

b. When there is no eye movement and no retinal movement. Signup and view all the answers

What happens if there is both eye movement and retinal movement?

a. An object is perceived as stationary. Signup and view all the answers

Which type of eye movement involves the smooth following of a moving target?

d. Smooth pursuit Signup and view all the answers

What is the characteristic of a saccade?

d. It is a rapid change in fixation from one object or location to another. Signup and view all the answers

When do the two eyes move in opposite directions in the context of eye movements?

d. During vergence. Signup and view all the answers

Which of the following best describes reflexive eye movements?

They are automatic and involuntary Signup and view all the answers

What is saccadic suppression?

The reduction of visual sensitivity that occurs during and before saccadic eye movements Signup and view all the answers

What is the primary purpose of saccadic suppression in the context of eye movements?

To stabilize the visual world by preventing blurring during rapid eye movements Signup and view all the answers

Which of the following is a way in which the visual system compensates for eye movements to maintain the stability of the visual world?

By shifting receptive fields of neurons in the parietal cortex toward the point of fixation. Signup and view all the answers

What happens to the receptive fields of neurons when a saccade is executed?

They are already processing information from the new location before the eye lands there. Signup and view all the answers

In addition to the parietal cortex, where do the receptive fields of neurons also shift inward toward the new point of fixation?

Frontal eye fields. Signup and view all the answers

Which of the following best describes the nature of saccades?

They tend to focus on 'interesting' points in an object or scene. Signup and view all the answers

How are the movements of the eye controlled?

By the contraction and relaxation of six eye muscles arranged in three pairs. Signup and view all the answers

Which of the following is not a pair of eye muscles involved in controlling eye movements?

Posterior Rectus Muscle and Anterior Oblique Muscle. Signup and view all the answers

Which brain structure is important for initiating and guiding eye movements?

Superior colliculus Signup and view all the answers

Study Notes

Optic Array and Motion Perception

The optic array is a structured pattern of light that changes as an observer moves through their environment.
Optic flow is the pattern of apparent motion of objects in a visual scene caused by the movement of the observer.
When an observer moves, optic flow describes the relative motion between the observer and stationary elements, enhancing depth perception.

Center of Vision and Optic Flow Field

The center of vision is the point around which optic flow appears to radiate, aiding in motion perception.
Shifts in the position of objects towards the center of the optic flow field provide information regarding their speed and direction relative to the observer.

Focus of Expansion (FOE)

The 'focus of expansion' is the point in the visual field from which optic flow emanates, indicating the direction of movement.
FOE is crucial for navigation, providing cues on the direction to travel and how fast to adapt movements based on changing environments.

Biological Motion Perception

Biological motion perception refers to recognizing and interpreting movements that are specific to living organisms.
This perception allows for the identification of intentions and emotional states based on movement patterns.
The phrase indicates that we can interpret motions in a general, albeit sophisticated, manner without needing intricate details.

Recognition and Brain Processing

Motion patterns in biological contexts can reveal information about the actions and identities of individuals.
The brain area involved in processing biological motion is the superior temporal sulcus, essential for understanding movement cues.

Time to Contact (TTC)

Time to Contact is the estimation of the remaining time before a moving object reaches an observer.
TTC can be calculated by dividing the distance to the object by its rate of approach.
Tau (τ) represents a ratio used to simplify TTC calculations, allowing the brain to make quick decisions.

Challenges in Motion Perception

The primary challenge in perceiving motion is distinguishing between actual movement of objects and the observer's own movement.
Retinal movement occurs when objects shift position on the retina due to the observer's movements, influencing motion perception.

Conditions for Perception of Movement

An object must change position relative to the background to be perceived as moving.
An object is viewed as stationary when it does not change position relative to the observer or background.
If both eye and retinal movements occur, discerning motion becomes complex due to conflicting signals.

Types of Eye Movements

Smooth pursuit eye movements allow the eyes to follow a moving target steadily.
Saccades are quick, abrupt movements of the eye when shifting focus between points.
Opposite eye movements occur during disconjugate eye movements, essential for aligning images from both eyes.

Reflexive Eye Movements and Saccadic Suppression

Reflexive eye movements are automatic responses to stimuli requiring focused attention.
Saccadic suppression minimizes motion blur during rapid eye movements, enhancing visual stability.

Stability and Eye Movements

The visual system compensates for eye movements to maintain a stable perception of the world.
Saccades trigger receptive fields in neurons to shift towards new fixation points, ensuring continuous updated information.
Besides the parietal cortex, the receptive fields also align inward toward the new fixation point in the frontal eye fields.

Control of Eye Movements

Eye movements are controlled by a complex interaction between the brain and muscle pairs that operate the eyes.
The ocular muscles involved in controlling eye movements include the superior and inferior rectus, but not all muscle pairs are equally involved.
The brain structure crucial for initiating and controlling eye movements is the brainstem, particularly areas like the superior colliculus.

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Description

Test your knowledge of the optic array concept as described by J. J. Gibson. Learn about the collection of light rays interacting with objects in the viewer's world and how it relates to visual perception. Find out if you can identify the correct definition among the given options.