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The ease with which a fish can reverse the effect of the sidedness of its eye asymmetry simply by turning around has caused biologists to study internal anatomy, especially the optic nerves, for the answer.

Would you please in a readily way throw a light on the bold part?

Any help would be appreciated

Source of the fish example

Excel 2010 for Dummies

Mammalian Subventricular Zones

  • Which of the words do you not understand? – tunny Nov 19 '14 at 18:32
  • reverse the effect of something – nima Nov 19 '14 at 18:37
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    Well, they appear to be used with their standard dictionary definition meanings. – tunny Nov 19 '14 at 18:41
  • undo the effect or make the effect not exist – Adam Nov 19 '14 at 18:41
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    One of your references uses "reverse the effect of the last edit" to explain what the undo function (CTRL+Z) does in Excel. I don't understand why that would be confusing, especially when you can see exactly what happens when you press the keys. Would you explain a little more why a dictionary hasn't helped? – ColleenV Nov 19 '14 at 18:50
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The original source of the line in question is talking about flatfish, and the 'eye assymetry' is the placement of both of the fish's eyes on the same side of its head (instead of the symmetrical, one-eye-on-each-side arrangement of most animals).

The 'effect of the sidedness of its eye asymmetry' is therefore the fact that it can only see things on one side of its body - on the right if both eyes are on the right side, or the left if both are on the left side. 'Reversing the effect ... by turning around' simply means that a left-eyed fish lying on its right side should see exactly the same thing as a right-eyed fish lying on its left side.

Sketch of flatfish

On the left is a flatfish with eyes on the left side, lying on its right side on the seabed. On the right is a flatfish with eyes on the right side in two different positions. The version on top is shown lying on its right side, exactly the same as the fish on the left, to demonstrate the asymmetry. The version below it has rolled over to lie on its left side, and in doing so reversed the effect of the asymmetry - it can now see the ocean above it, just like the left-eyed fish, instead of burying its eyes in the mud.

That is, the sentence is claiming that it shouldn't make any difference whether the fish's eyes are on the right or the left side, because all it has to do is roll over and it will get the same effect as a fish with eyes on the other side of it's head would have had without rolling over.

(The reason this is significant is because starry flounder living hear Japan are almost all left-eyed - despite the fact that those by the US are split half-and-half - which indicates that it is having an effect. The question is what, since it can't be to do with looking at the environment around it...)

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  • I cannot get this: That is, the sentence is claiming that it shouldn't make any difference whether the fish's eyes are on the right or the left side, because all it has to do is roll over and it will get the same effect as a fish with eyes on the other side of it's head would have had without rolling over. – nima Nov 24 '14 at 17:45
  • could you show me an image so as to clear it better?The fish's eye is still asymmetrical, but the expected effect of that asymmetry is canceled out when the fish turns around. – nima Nov 24 '14 at 17:50
  • My specific problem is understanding or creating an image of this explanation: fishes quickly turn around their head to judge not only the depth but also to get a complete picture of the object heading toward it. – nima Nov 24 '14 at 17:58
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    @nima_persian It probably helps if you think of this turning around as turning their bodies around (so that they lies on their stomachs when they swim), not turning their heads around quickly during swimming. – Damkerng T. Nov 24 '14 at 19:47
  • It might help to bear in mind that it is not that the fish's eye is asymmetrical itself - the positioning of the eyes on the head is. – Toby Y. Nov 24 '14 at 20:16
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If X reverses the effect of Y's Z, it means:

  • Z changes some aspect of Y
  • X will bring that aspect of Y into a state that's the same as if Z didn't do anything.
  • Usually this is by removing or undoing Z, but it's possible another action has been performed that cancels out Z.

The ease with which a fish can reverse the effect of the sidedness of its eye asymmetry simply by turning around has caused biologists to study internal anatomy, especially the optic nerves, for the answer.

"It" is a fish

  • "Sidedness of its eye asymmetry" is changing the fish (the fish's vision)
  • "Simply by turning around" brings the fish into a state where the fish's "sidedness of its eye asymmetry" no longer changes the fish's vision.
  • The fish's eye is still asymmetrical, but the expected effect of that asymmetry is canceled out when the fish turns around.
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    I don't think "reverse the effect" in OP's example means "cancel out the effect" (so it's as if nothing had happened). Surely it means the "chirality/handedness" (I really can't be doing with "sidedness") of the fish's vision will switch to favouring left over right (or up over down, or whatever), being the opposite of what it did before? – FumbleFingers Reinstate Monica Nov 20 '14 at 0:09

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