Take the sentence
Students who study physics rigorously learn math.
As it stands, 'rigorously' can modify either 'study' or 'learn'. But if we move the adverb to the front to get
Rigorously, students who study physics learn math.
'rigorously' unambiguously modifies 'learn' and not 'study.' This should be clear to any native speaker of English. However, when I think about it this phenomena, it's not clear at all why this must be the case. After all, might it not be more logical for the adverb to modify the closest verb? What are the (scientific) explanations of this sort of syntactic behavior?