Transcript chapter7

Chapter 7:
Taking Action
The Ecological Approach to Perception
• Approach developed by J. J. Gibson (began
in late 1950s)
– Gibson felt that traditional laboratory
research on perception was:
• too artificial - observers were not
allowed to move their heads.
• unable to provide an explanation for how
pilots used environmental information to
land airplanes
The Ecological Approach to Perception continued
• Optic array - structure created by the
surfaces, textures, and contours in the
environment
– Optic flow - appearance of objects as the
observer moves past them
• Gradient of flow - difference in flow as a
function of distance from the observer
• Focus of expansion - point in distance
where there is no flow
Optic Flow
– Self-produced information - flow is created
by the movement of the observer
– Invariant information - properties that
remain constant while the observer is
moving
Figure 7-1 p154
Figure 7-2 p154
Self-produced Information
• Somersaulting
– Could be performed by learning a
predetermined sequence of moves; thus
performance would be the same with and
without vision
– Bardy and Laurent found that expert
gymnasts performed worse with their eyes
closed.
• They use vision to correct their
trajectory.
• Novice gymnasts do not show this effect.
Figure 7-3 p155
Figure 7-4 p155
The Senses Do Not Work in Isolation
• Experiment by Lee and Aronson
– 13- to 16-month-old children placed in
“swinging room”
• In the room, the floor was stationary but
the walls and ceiling swung backward
and forward.
• The movement creates optic flow
patterns.
– Children swayed back and forth in
response the flow patterns created in the
room.
The Senses Do Not Work in
Isolation - continued
– Adults show the same response as
children when placed in the swinging room.
• Results show that vision has a powerful effect
on balance and even overrides other senses
that provide feedback about body placement
and posture.
Figure 7-5 p156
Navigating Through the Environment
• Optic flow neurons - neurons in the medial
superior temporal area (MST) of monkeys
respond to flow patterns
• Experiment by Britten and van Wezel
– Monkeys were trained to respond to the
flow of dots on a computer screen.
• They indicated whether the dots flowed
to the right, left, or straight ahead.
Figure 7-6 p157
Figure 7-7 p157
Figure 7-8 p158
Navigating Through the
Environment - continued
• Experiment by Britten and van Wezel
– As the monkeys did the task,
microstimulation was used to stimulate
MST neurons that respond to specific
directions of flow patterns.
– Judgments were shifted in the direction of
the stimulated neuron.
Figure 7-9 p158
Driving a Car
• Experiment by Land and Lee
– Car fitted with instruments to measure
• Angle of steering wheel
• Speed of vehicle
• Direction of gaze of driver
– When driving straight, driver looks straight
ahead but not at focus of expansion
Experiment by Land and Lee - continued
• When driving around a curve, driver looks at
tangent point at side of the road
• Results suggest that drivers use other
information in addition to optic flow to
determine their heading.
– They might be noting the position of the car
in relation to the center line or side of the
road.
Figure 7-10 p159
Walking
• Visual direction strategy - observers keep
their body pointed toward a target
– Walkers correct when target drifts to left
or right
• Blind walking experiments show that people
can navigate without any visual stimulation
from the environment.
Figure 7-11 p159
Figure 7-12 p160
Wayfinding
• Landmarks involved taking routes the
involves making turns
• Landmarks are objects on the route that
serve as cues to indicate where to turn.
Figure 7-13 p160
Figure 7-14 p161
Wayfinding - continued
• Experiment by Janzen and van Turennout
– Observers studied a film that moved
through a “virtual museum.”
– They were told that they should be able to
act as a guide within the museum.
– Exhibits appeared both at decision points
where turns were necessary and nondecision points.
Experiment by Janzen and van
Turennout - continued
• Observers were given a recognition task
while in an fMRI.
– They were presented objects they had
seen as exhibits, and ones they had not
seen.
• Results showed the greatest activation for
objects at decision points (landmarks) in the
parahippocampal gyrus.
Figure 7-15 p161
Effects of Brain Damage on Wayfinding
• Retrosplenial cortex damage
• Maguire (2006)
– Patient T. T.
– Parahippocampus gyrus
– Retrosplenial cortex
– Hippocampus
Figure 7-16 p162
Figure 7-17 p162
Affordances - What Objects Are Used for
• Gibson believed affordances of objects are
made up of information that indicates what an
object is used for.
– They indicate “potential for action” as part
of our perception.
– People with certain types of brain damage
show that even though they may not be
able to name objects, they can still
describe how they are used or can pick
them up and use them.
The Physiology of Reaching and Grasping
• Neurons in the parietal lobe that are silent
when a monkey was not behaving, fire when
the monkey reached to press a button to
receive food.
– This response only happened when the
animal was reaching to achieve a goal.
Figure 7-18 p164
The Physiology of Reaching and
Grasping - continued
• Experiment by Connolly - evidence for PRR in
humans
• Fattori – three different regions are used in
grasping
• Schindler – obstacle avoidance is controlled
by the parietal regions
Figure 7-19 p165
Figure 7-20 p165
Figure 7-21 p166
Mirroring Others’ Actions in the Brain
• Mirror neurons in the cortex of monkeys that
– Respond when a monkey grasps an object
and when an experimenter grasps an
object
– Response to the observed action “mirrors”
the response of actually grasping
– There is a diminished response if an object
is grasped by a tool (such as pliers).
Mirror Neurons in Premotor Cortex continued
• Possible functions of mirror neurons
– To help understand another animal’s
actions and react to them appropriately
– To help imitate the observed action
• Audiovisual mirror neurons - respond to
action and the accompanying sound
• Mirror neurons may help link sensory
perceptions and motor actions.
Video: Mirror Neurons
Figure 7-22 p167
Figure 7-23 p167
Predicting People’s Intentions
• Iacoboni (2005) – mirror neurons can be
influenced by different intentions
Figure 7-24 p168
Figure 7-25 p168
Action-Based Accounts of Perception
• The traditional approach to perception is
focused on how the environment is
represented in the nervous system
• According to action-based accounts of
perception the purpose of perception is to
create a representation in the mind of
whatever you are looking at