Which sleights use Retention?

Jun 18, 2019
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It's a bit difficult to digest the fact that our brains basically favour magicians in such a HUGE manner, by allowing retention in vision, yet we only use it for coin vanishes.

So I attribute it to my incomplete knowledge in magic.

Can anybody tell me what other sleights use retention of vision specifically? Card sleights? Magic with other props? Or even any ruse stage magicians use?
 
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Mar 9, 2014
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It depends how broadly we consider the psychological phenomena which gives rise to the retention of vision effect. The imperfections of the human visual system and the tendency of human brains to make assumptions based on incomplete or inaccurate information are widely exploited in magic, although their specific application to retention of vision illusions may be relatively rare (I can't say for sure, I know more about neuroscience than magic history :) ). Not really an answer to the question you posed, but I'm just trying to point out that, while magicians may not widely exploit this specific illusion, they certainly make good use of the underlying mechanisms.

Cups and Balls sort of has an element of retention of vision, to the extent that the loads/steals are often done in a transitive action, and the brain merely sees a cup lifted to reveal (or not reveal) a ball before being placed back down with no change. Depending on the version, the "retention" may be emphasized or may simply act as one of many subtle details.

Any card switch or card change done under minimal cover is a form of retention of vision in a way, since the brain experiences continuity in an instance where the action is actually interrupted.
 
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RealityOne

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I think that most of them have been covered. Vanishes of coins, sponge balls, cups & balls, billiard balls and card vanishes rely on the retention of vision. In cups & balls, there are some more advanced vanishes that rely a similar principle to be convincing - the continuation of motion. That is, the ball is seen in motion between points A, B and C and then appears at point F and the brain assumes that to get there it traveled through points D and E. Essentially, both retention and continuation of motion are applications of Newton's Law of Inertia because the spectator does not see the external force acting upon the object. Or, put simply a selection of reality is a distortion of reality (see signature).

So, if you expand the retention of vision concept into the memory of presented events augmented by the expected intermediate steps or logical outcomes, you have many principles of parlor or stage magic. For example, if I put a chicken into a box, the expectation is that it remains in the box until you see it taken out. If I put an egg into a bag, the expectation is that it remains there until it is taken out. In essence, it is retention of memory. The magic works because previous, concurrent or subsequent actions are not remembered and therefore the force required to alter the Law of Magical Inertia is not remembered.

So I come full circle to argue that retention of vision is merely one form of retention of memory.
 
Jun 18, 2019
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With cards things like the rub a dub vanish or a tent vanish come to mind. I’m sure there is others but I’m not really much of a card guy. Sponge stuff has plenty of retention style vanishes too.
Aha, yes, I overlooked the rub a dub vanish. Thanks!

Essentially, both retention and continuation of motion are applications of Newton's Law of Inertia because the spectator does not see the external force acting upon the object.

I was under the impression however that retention of vision is just a more conjuring-related term for the phenomenon known otherwise as persistence of vision. Newton's laws are applicable only to Classical Physics related with material objects more than visions. Am I missing something here?


So I come full circle to argue that retention of vision is merely one form of retention of memory.
True.

Thanks a lot everybody! :) :)
 

RealityOne

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I was under the impression however that retention of vision is just a more conjuring-related term for the phenomenon known otherwise as persistence of vision. Newton's laws are applicable only to Classical Physics related with material objects more than visions. Am I missing something here?

Retention of vision is the optical illusion, continuation of motion (inertia) is the mental conclusion. They are mutually reinforcing.
 
Nov 3, 2018
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I was under the impression however that retention of vision is just a more conjuring-related term for the phenomenon known otherwise as persistence of vision. Newton's laws are applicable only to Classical Physics related with material objects more than visions. Am I missing something here?
If I understand correctly (and that's a pretty big "if", in this case), Newton's Law was meant to be an analogy, rather than a literal application of physics. To rephrase it, the spectator's mind sees the coin travel in the direction of your left hand, and as it doesn't perceive any outward force (i.e. the magician's right fingers curling in to get the coin into palm), he assumes that the motion is completed -- that the object in question follows Newton's Law of Inertia and keeps the direction it was headed to.
 
Jul 26, 2016
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I am far from an expert on this, but this thread got me interested in doing a wee bit of research. From what I have read, the optical illusion that accounts for a spectator's retention of vision of an object when a retention pass is properly executed, falls more within the sciences of optics and neuroscience, than physics. When light strikes either the rods or the cones of the eye's retina, it's converted into an electric signal that is relayed to the brain via the optic nerve. The brain then translates the electrical signals into the images a person sees.

An object (e.g. a coin) displayed for a short length of time leaves an image on the retina that may persist for a further short time after the object has actually disappeared from view. What happens is that the retina still retains a fleeting image of the coin for a fraction of a second after the fingers of the hand in which the coin is (supposedly) placed are apparently closed over the coin. Accordingly, the spectator will be convinced that the coin was actually placed in the hand, when in fact it wasn't.
 
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RealityOne

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he assumes that the motion is completed -- that the object in question follows Newton's Law of Inertia and keeps the direction it was headed to.

Exactly.

leaves an image on the retina that may persist for a further short time after the object has actually disappeared from view.

Which provides "cover" for the "force" applied and lead to an assumption that the object is in the hand.
 
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Jun 18, 2019
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West Bengal, India
Well, I don't know if Newton's laws are analogies. We're taught them as literal explanations of Classical Physics, even though those principles do hold up insanely well as metaphors. For example, it's easier to continue doing something you are already doing than STARTING something or picking something up after you had quit it for a long time.

Regardless, my query related to magic itself has been solved. :D

Thanks!

:)
 
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