Perception and Action part 1 Flashcards
(39 cards)
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.
