Perception and Action part 1 Flashcards
Srinivasan, Lehrer & Horridge (1990)
Honey bees were trained to land on ‘flowers’ (small disks with sugar solution)
When the disks were patterned against a patterned background, they were not detected, only when the disk was raised by 2 cm (3D perception)
Bees show a strong tendency to land on the edge of the disks, facing inwards
tinbergen 1951
Turn back and look
Fast mapping procedure during turns in the flight away from the target
Cartwright and Collett (1979)
6 flights were needed for generating a map
20 flights were needed to land at the correct angle
Cartwright and Collett (1983): ‘Snapshot model’
JJ Gibson IN THE LATE 1950S felt that traditional laboratory research on perception was:
too artificial and not ECOLOGICALLY VALID
observers were NOT ALLOWED to MOVE their heads
stimuli were STATIC
Gibson put forward the point of view that
motion contributes considerably to visual perception.
Perceptions are extraction of invariants from an environment which is dynamic because we move in it (optical flow)
4 Central Concepts in Gibson’s Theory
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 ( THE POINT AT WHICH A PILOT LOOKS IN THE DISTANCE -there is no flow)
OPTIC ARRAY…..?
The patterns of light reaching the eye can be thought of as an optic array containing all the visual information available at the retina. This optic array provides unambiguous information about the layout of objects in space.
Bottom-up processing
GIBSONS theory was a bottom up processing theory
is also known as data-driven processing, because perception begins with the stimulus itself. Processing is carried out in one direction from the retina to the visual cortex, with each successive stage in the visual pathway carrying out ever more complex analysis of the input.
Top-down processing
refers to the use of contextual information in pattern recognition. For example, understanding difficult handwriting is easier when reading complete sentences than when reading single and isolated words. This is because the meaning of the surrounding words provide a context to aid understanding.
OPTIC FLOW
3 TERMS
S I E
Self-produced information - flow is created by the movement of the observer (WORLD MOVES PAST BECAUSE THE OBSERVER MOVES)
Invariant information - properties that remain constant while the observer is moving ( A LAND MARK)
Extraction of information that is constant from an environment that is in motion (KEEPING SIGHT OF A LAND MARK WHEN MOVING)
MOVEMENT CREATES FLOW. FLOW PROVIDES …….
INFORMATION FOR MORE MOVEMENT.
Optomotor Response……?
Optic Flow determines the movement
Kalmus and his fly in 1949
Kalmus 1949
Walls with gratings (stripes) were used to test the influence of visual flow perception on movement of the body
When the wall is moving, the grating simulates the optic flow
Kalmus (1949): A fly turns into the same direction as the gratings move
optomotor response = optic flow determines the movement
Blondeau & Heisenberg (1982)
when the drum from kalmus experiment was rotated in deferent directions the Fly makes complicated turns to adjust to the grating
the swing room
Similar type of ‘optomotor response’ in humans in the ‘Swinging room’ (Lee & Aronson, 1974; Lee & Lishman, 1975; Lee & Young, 1986)
13- to 16-month-old children and adults placed in “swinging room”
In the room, the floor was stationary, but walls and ceiling swung backward and forward
The movement creates optic flow patterns
Visual flow and body balance
13-16 months old infants would sway along with the room, stagger or even fall
Adults sometimes overcompensated in the opposite direction
Results show that vision has a powerful effect on balance and can even override conscious efforts to maintain posture
Somersaulting
Somersaulting could be performed by learning a predetermined sequence of moves
Expectation was that performance would be the same with and without vision
Bardy and Laurent (1998) found that expert gymnasts performed worse with their eyes closed
Experts gymnasts used vision to correct their trajectory, but novice gymnasts did not
visual flow and body balance in the swing room
13-16 months old infants would sway along with the room, stagger or even fall
Adults sometimes overcompensated in the opposite direction
Results show that vision has a powerful effect on balance and can even override conscious efforts to maintain posture
People can determine to which point they are heading with an accuracy of
0.5 to 1 degree (Warren, 1995)
Land and Lee (1994) fitted a car with instruments to measure
Angle of steering wheel
Speed of vehicle
Direction of gaze of driver
The Physiology of Navigation
which areas are active during navigation
Pre Motor (Mirror area)
Posterior Parietal
Medial Superior temporal area
Animal research looked for single cell responses
Optic flow neurons -
neurons in the medial superior temporal area (MST) of monkeys respond to flow patterns
different neurons in the MST
Medial Superior Temporal area take on
different tasks in the analysis of the optic flow
MST Medial Superior Temporal Medial Superior Temporal Medial Superior Temporal Medial Superior Temporal Medial Superior Temporal
Britten and van Wezel (2002)
Britten and van Wezel (2002)
Monkeys were trained to respond to the flow of dots on a computer screen.
Monkeys indicated whether the dots flowed to the right, left, or straight ahead.
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.
Experiment by Maguire et al. (1998)
Observers learned the layout of a “virtual town”
In a PET scanner, they were told to navigate to locations in the town
Navigating activated the right hippocampus and part of the parietal cortex
Activation was greater when the navigation between points was accurate than when it was inaccurate
Observers studied a film that showed them through a “virtual museum” (Janzen & Van Turennouts, 2004)
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 non-decision points
Results showed the greatest activation for objects at decision points (landmarks) in the parahippocampal gyrus
TURNING POINTS ARE essential for navigating in space
London cab drivers played an interactive computer game with accurate depictions of London streets (Spiers and Maguire, 2006)
They were given instructions to drive towards a destination.
In mid-route, the destination was changed
They also heard a statement unrelated to the destination
After the trip was finished, they viewed a playback and were asked what they were thinking at different points
Spiers and Maguire looked at what for the first time in their virtual reality test with cab drivers
thinking protocols and brain scans
Affordances – Visual Object Function
Gibson believed that you can SEE affordances of objects, i.e. there is visual information in the object about function
Affordances 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 Cups Experiment
Patients with damage to parietal lobe can show extinction - the inability to direct attention to more than one thing at a time
The left cup on the left was not detected unless there was a handle added
The fake handle did not support object detection on the left side (random choice)
Researchers concluded that the affordance for grasping may have been activating a specific network in the brain
Affordances indicate…..
“potential for action” as part of our perception
Carlton et al. (2002) identified these neurons responding specifically to goal-directed actions in the parietal reach region (PRR)
Parietal Reach Region (PRR)
who detected neurons responding to specifically goal directed actions in the PRR
Parietal Reach Region
Carlton et al in 2002
Observers looked a fixation point and were given a cue for the location of a target (Connolly et al. 2003)
After a nine-second interval, they pointed to the target
Delay: Keep the target in mind
Control condition: Just wait and see
Higher FMRI activation in the PRR region during the delay
WHEN THEY WERE THINKING ABOUT REACHING……THE PRR WAS ACTIVATED
PARIETAL REACH REGION
Neurons in the premotor 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 food was grasped by a tool (such as pliers) instead of hands NONSENSE-ACTIONS
Overlap of Perception and Action
Firing occurs when the monkey sees
experimenter breaks peanut which produces a sound
experimenter breaks peanut
experimenter produces sound
monkey itself breaks peanut and hears sound
ACTION FEATURES ARE ENCODED
ACTION FEATURES ARE ENCODED
Overlap of Perception and Action
FIRING OCCURS when the monkey sees
experimenter breaks peanut which produces a sound
experimenter breaks peanut
experimenter produces sound
monkey itself breaks peanut and hears sound
ACTION FEATURES ARE ENCODED
Mirror Neurons in Premotor Cortex
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
Experiment by Calvo-Merino et al. (2005)
Tested three groups
Professionally trained ballet dancers
Professionally trained capoeira dancers (Brazilian dance with karate-like movements)
Control group of non-dancers
They watched two videos
One with standard ballet movements
One with standard capoeira movements
Pre-motor cortex activation was
Greatest for ballet dancers while watching ballet
Greatest for capoeira dancers while watching capoeira
Same response for both for non-dancers
WATCHING YOUR OWN DISCIPLINE ACTIVATES THE PRE MOTOR CORTEX.
