Topic 6: Movement and Action Flashcards
Explain the ecological approach to perception
Focuses on specifying the information in the environment used for perception
Emphasis on the study of moving observers to determine how their movement results in perceptual information that both creates their
perception and guides further movement
According to the ecological approach to perception, what causes you to perceive movement in stationary objects if you are moving?
Your movement relative to the objects
Flow of stimuli in the environment that occurs when an observer moves relative to that environment
Optic flow
Provides information about speed/how fast the observer is moving
Gradient of flow
Where the observer will end up if course is not changed
Focus of expansion (FOE)
What are the two important characteristics of optic flow?
Optic flow is more rapid near the observer, and is slower farther away
No flow at the destination toward which the observer is moving (white dot)
Describe a procedure measuring Reacting to Information Created by Movement
Have observers judge, based on optic flow, where they would be heading
relative to a reference point.
Typically done using computer-generated displays that create illusions of
optic flow but can also get a sense from stationary images as well.
The ability to stand up straight and keep balance depends on the interactions between…
Vestibular system, somatosensory system, visual system
What do swinging room experiments demonstrate?
Vision can override other sources of
balance information provided by the inner ear and the receptors in the muscles & joints.
What visual direction strategy do we typically employ?
keep our body oriented/pointed toward the target
Awareness of our position in an environment
while we move
Spatial updating
Ability to navigate short distances in the
complete absence of visual stimuli
Muscle movements = indication of speed
and direction
Success depends on combining these
muscle movements + memory for target
location
Travel to distant destinations that aren’t
immediately visible.
Wayfinding
What does wayfinding involve?
Perceiving objects in the environment
Remembering these objects and their relation to the overall scene/environment
Knowing when to turn, and in what direction
Why are landmarks an important source of information for wayfinding?
Objects on a route that can serve as cues to indicate where to turn
Typical maze tasks contain…
Decision-point landmarks: objects at corners where a decision needs to be made to turn or not
Non-decision-point landmarks: objects that provide no critical information for navigation
What is the relationship between memory and landmarks?
Individuals spend more time looking at decision-point landmarks and are more likely to
remember them.
How did early research begin to conceptualize cognitive maps?
Studied how rats learned to run through mazes to find rewards
Where are place cells found in humans?
Entorhinal cortex
Groups of neurons that fire when in a specific spot, and only in that spot
Place cells
Information about how an object can be used
Affordances
Major brain region in the dorsal stream
for reaching and grasping objects
Parietal reach region
Describe the size-weight illusion
Erroneously predicting weight when
perceiving two differently sized objects
that have the same weight.
Error occurs because we tend to
predict that objects we perceive as
being bigger = more force to lift
What are the implications of research showing that when you deliver and perceive a hit to an object, the force of your grip increases exactly when the hit is delivered
Motor system correctly predicts the timing and force.
Typically, we perceive motion when either…
- An image moves across our retina.
- We move our eyes to follow something that is moving in our field of view.
the real, physical movement of a stimulus
Real motion
The perception of motion of stimuli that aren’t moving
illusory motion
What are the three types of illusory motion?
Apparent motion
Induced motion
Motion aftereffects
Occurs when the motion of one object causes a nearby stationary object to appear to move.
Induced motion
Occurs when viewing a moving stimulus causes a stationary stimulus to then appear to move
Motion aftereffects
When Jack walks from left to right and you
move your eyes to follow him, portions of
the environment become covered as he
walks by them, and then uncovered when
he moves on. What does this create?
A local disturbance in the optic array
Indicates that it is the observer who is moving
(either moving their eyes or entire body), and
not an object in the environment.
Global optic flow
What are the three signals associated with corollary discharge theory?
- A motor signal (MS): Indicates you have moved your eyes.
- An image displacement signal (IDS): indicates an image has moved on the retina.
- A copy of motor signal (CDS – corollary discharge signal)
According to corollary discharge theory, movement is perceived when…
Comparator receives one, and only one,
of either the CDS or the IDS
Accoridng to corollary discharge theory, if the comparator receives both signals…
No movement is perceived
Which brain areas are associated with the “comparator” (Corollary discharge theory)?
V1 is important for preliminary
processing, motion perception is also a
function of activity in the middle temporal
area (MT) -Previously referred to as V5
In extreme cases of bilateral damage to the middle temporal lobe, you can get…
Akinetopsia (lose the ability to perceive visual motion)
Receptive fields in the MT are…
Directionally selective
Occurs when only a portion of a moving stimulus is seen, as though viewed through a narrow aperture or in the view of a single neuron’s receptive field
Aperture problem
What is the solution to the aperture problem?
Visual system pools the responses from several MT neurons at once to get a “truer” picture of how something is moving
