jaleh"As proof of principle ..."What does this expression at the begining of a sentence mean?

Nothing to me. What is the rest of the sentence?

As proof of principle, the researchers showed that their analytical protocol had detected a second neural pathway in the brain for which scientists already had evidence — this one tuned to the sounds of human speech.

Scientists often develop theories (hypotheses) that only work "in principle" -- not in the real world.

jaleh"As proof of principle ..."What does this expression at the begining of a sentence mean?

This expression begins a sentence that explains how a real world example shows that the principle is true.

The scientists guessed (suspected) that a principle

Many thanks. you explained it very clearly.