Mommy, Mommy, Mommy, Mommy, Mommy...

How have children as young as mine already grabbed the concept of the "squeaky wheel?" Though I love their little voices with all my heart, almost nothing sets my teeth on edge like the constant repetition of "Mommy, mommy, mommy, mommy, mommy..." It frustrates me that I respond to it, just to stop it, because I know that in the long run they just decide that that is an effective way to get my attention. Yet, it does make you respond just to get them to stop. Very frustrating. Anyone have any brilliant ideas?