Seconding what Sedaka said. Perception of stilled objects as opposed to moving objects are two slightly different processes.
You can be great in one but quite bad in the other.
Usually, both abilities are on about the same level and at least average. So it's quite true for many people that if they can do either A (or B), they most likely will have no trouble with B (or A) as well.
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Autism + ADHD
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The trouble with having an open mind, of course, is that people will insist on coming along and trying to put things in it. Terry Pratchett