Catching 6 Flashcards
What is judging time to contact? TTC
When catching, the only information available about the speed and time is from the visual field of the object approaching you
What is optic looming
Changes as the object approaches as it gets close it fills the visual field
What did Gibson 1954 find about optic looming
Approach to an object is specified by a magnification of the closed contour
It expands rapidly just before the object reaches you
Cannot be hit by object in TTCs
Apparent size of object (at eye)
Change in size of object (at eye)
How do we judge time to collision
Relative time of dilation of image on retina specifies when an object will collide with you
Little requirement to know about object, distance, speed
What is ecological optics
Information is rich, transforming, optic array
Doesn’t rely on experiences of world, or construct of a whole scene
It is a direct perception
What is top down interpretation
Face cognition resources applied to perception, two faces appear in a hollow mask
What is bottom up reconstruction
Nothing top down for the brain to latch onto
In a change between dots you can see a triangle and the brain is responding to every single point of light in one frame and the next
What happens when diving gannets dive
Recorded time taken to dive and worked out when birds followed their wings
They fold them a second after they start plummeting, but the longer the dive the longer it takes them to fold their wings
Consistent with the use of Tau
What are two considerations of Testing Tau
- Tau is based in changing the optical size of the object as it approached so the change in optical size is independent of distance or speed
- Consider what other variables might do the same job, and see the effect of adding or taking them away
What did Wann do testing tau
He manipulated looming information about a ball
When looming (tau) indicated earlier arrival people grasped on the basis of this
However when stereo information indicated an earlier arrival they also grasped
Suggesting tau may be the primary source but when combined with binocular information
Reliance on it varies across conditions and activity
What did Bennet 2010 find about TTC
Gauging TTC is improved by tracking an approaching object
Large symmetric objects (footballs) approaches your head you look at it
But in cricket, it seems that tau and binocular information are not used in initial trajectory of the ball when batting but may play a role after the ball bounces
Eye movements are important for retrieving info about the balls trajectory above tau
What are some problems for tau
Ball sports balls are rounded and symmetrical but there are other cases where tau isn’t useful (badminton)
Not all objects loom steadily
Prior knowledge of objects causes TTC judgments to change- if we know it’s a tennis ball and it was closer than a basketball we’d know we needed to catch that first
How does catching develop with age
3 years old, can’t respond quickly enough
7 years old, success at catching, reaching out at the right time
