Chapter 7 and 8: Taking Action and Perceiving Motion

Question 1

What is optic flow and it’s key characteristics?

Answer 1

Optic Flow: movement of an observer creates movement of objects and scenes relative to the observer.

Characteristics of Optic Flow:

• Optic flow is more rapid near the moving observer. This is called gradient of flow and it tells the observer how fast they are moving
• There is no flow at the destination towards which the observer is moving. The absence of flow at the destination is called the focus of expansion.

Question 2

How do our senses work together for balance?

Answer 2

Our vision provides us with a frame of reference which helps our muscles make constant adjustments to maintain balance.

Question 3

What are affordances?

Answer 3

Affordances is information that indicates how an object can be used. Potential action is part of how we perceive objects.

Question 4

How do we keep our course when walking?

Answer 4

When walking, we use a visual direction strategy where people keep their body pointed towards their goal. Spatial updating is the process by which we keep track of our position within a surrounding area while they move.

Question 5

What is wayfinding?

Answer 5

Wayfinding is navigation where we take a route that involves making turns, traveling to a destination that is not immediately visible. When we are wayfinding, landmarks are used for finding our way. The parahippocampal gyrus is particularly important as well for navigation.

Question 6

What neurological structures are involved in reaching and grasping?

Answer 6

AN interaction from the dorsal and ventral pathway is important.

The parietal reach region is specifically involved in reaching and grasping
- Visuomotor neurons in the parietal reach region respond to specific types of hand grips and to objects that require that grip.

Question 7

What is preprioception?

Answer 7

the ability to sense body position and movement

Question 8

What is the size-Weight illusion?

Answer 8

Erroneously predicting the weight of something due to assumptions based on it’s size.

Question 9

What are mirror neurons?

Answer 9

Mirror neurons respond both when watching someone complete an action and when doing the action yourself.

These neurons can be influenced by the perceived intention behind the action beyond just the action itself.

This suggests that mirror neurons are responding to the action that is happening plus the expected sequence of events that will follow.

Question 10

What is the Action-Specific Perception Hypothesis?

Answer 10

People perceive their environment in terms of their ability to act on it.

Question 11

What are audio-visual mirror neurons?

Answer 11

A type of mirror neuron that respond to the pattern of motion associated with an action AND to the sounds associated with the action.

Question 12

What are the five main functions of motion perception?

Answer 12

1. Detecting things: movement makes objects more salient in our environment
2. Perceiving objects: our own motion allows us to view objects from different angles
3. Perceiving Events: we observe ongoing behaviour as a sequence of events where events are segments of time at a particular location and changes in motion are often used to create boundaries between events.
4. Social Perception: we use movement as cues for a person’s intentions and emotions
5. Taking Action: we use movement cues to guide our action

Question 13

What is Illusory Motion and it’s different types?

Answer 13

Illusory motion: the perception of movment when the stimulus is actually stationary

Types of Illusory motion:
- Apparent Motion: perceiving motion when two stimuli are flashed with the correct timing between them

• Induced Motion: When the motion of one object (usually larger) cases nearby stationary objects (usually smaller) to appear to move
• Motion after Effects: when viewing a moving stimulus causes stationary stimulus to appear to move. (e.g. the waterfall illusion)

Question 14

What is the optic array and how does it contribute to motion perception?

Answer 14

The optic array is the structure created by surfaces, textures, and contours in the environment.

Local disturbances in the optic array occur when an object moving through the environment covers and then uncovers sections of the stationary background.

Question 15

How does corollary discharge theory relate to motion perception?

Answer 15

There is motion that we follow with our eyes (MS causes CDS but there is no IDS because the object is also moving therefore we perceive motion)

There is motion and we keep our eyes still (IDS because the image moves across our retina, but no CDS because there was no motor movement).

Question 16

What is the Reichardt Detector ?

Answer 16

IT is a circuit that consists of 2 neurons (A & B) which send their signals to an output unit that compares the signals. A delay unit slows the signal from A.

The output unit multiples the responses from A & B to create movement signals that result in the perception of motion.

Question 17

Why is it suspected that the middle temporal area is specialized for processing motion?

Answer 17

Because the Middle Temporal Area contains directionally sensitive neurons.

Question 18

What is the aperture problem? How do we solve it?

Answer 18

When we focus on one small portion of a stimulus, it can distort perception and confuse our understanding of motion. The firing pattern of one neuron is not enough to provide complete information about motion. To solve this we pool information from multiple neurons. We can also focus on corners or edges to reduce this problem.

Question 19

What type of motion do we perceive best? Why is it unique?

Answer 19

We perceive biological motion best because we see it the most often.

It is unique because we will normally perceive movement as following the shortest path but in biological motion, we understand the constraints of our physiology which we apply when perceiving motion.

Question 20

What is representational momentum?

Answer 20

When we see stationary images which imply motion, we tend to continue the motion in our mind.

Question 21

How does driving navigation differ from walking?

Answer 21

Drivers don’t look at the focus of expansion, they focus on a point in front of the car.

When turning or driving on curves, drivers look at edges of the road to guide movement.

Question 22

What are different types of landmarks and which do we use more often?

Answer 22

Non-decision point landmarks are landmarks located at points where we don’t have the option to change direction. These can be helpful to confirm we are going in the correct direction but they are not used as often.

decision point landmarks are landmarks located at points where we have to make a decision about which direction to go. These are used more often and remembered more easily.

Question 23

How is navigation affected by damage to the retrosplienial cortex? What about the hippocampus?

Answer 23

Retrosplenial cortex: difficulty with directional ability

Hippocampus: inability to retrieve stored spatial information such as memory for routes.

Question 24

What is optic ataxia?

Answer 24

When a person is unable to accurately point to objects and has difficulty accommodating reach position to avoid occluding objects.

Is caused by damage in the parietal lobe.

Question 25

What is global optic flow?

Answer 25

The idea that we perceive motion when one part of he visual scene moves relative to the rest of the scene. We don’t perceive motion when the whole visual scene moves together.