[Ahmed Abdullah]

Each proton has it's own magnetic field so it should effect the magnetic field of all nearby proton whether it is homologous (equivalent) or not. I don't understand how this discrimination arise?
How a proton understand "that proton is like me so I shoudn't . ... ... " I mean it's ridiculous.
I am not really getting it. Please help me.
Can anyone explain the theory, please? 

[Ahmed Abdullah]

Is it possible that homologous or equivalent protons are somehow connected with each other in the sense that they all change orientation in synchronous fashion and can't do it independently from each other?

[Smrt guy]

Protons don't recognize each other as equivalent.  Instead, the rotation about single bonds is so fast that the protons are indistinguishable.  That is, on one pulse the hydrogens are oriented in a certain way.  On the next pulse, they can be mixed up and one H might be in a position that another had been in at the time of the previous pulse.  The result is that the instrument sees an average.

[orgopete]

I think it is a little more complicated than that (though I cannot give a good explanation). If you have two adjacent hydrogens that may even split each other, they may appear as two separate doublets if their chemical shifts are distant from one another. If their chemical shifts were closer together, you would find that the inner peaks of the doublets would have a greater intensity than the outer peaks. If you wished to calculate the chemical shifts and coupling constants, you would need to do a different calculation as the coupling shift from first order. If the chemical shifts become closer together, the inner peaks would continue to grow in intensity and the outer peaks would become wider and weaker. If the two hydrogens had the same chemical shift, they would no longer appear to split each other. This is the case for a compound like 1,2-dimethoxyethane. Even though the CH₂-groups could split each other, because they have the same chemical shift, that coupling is lost. There are two singlets in the NMR.