Why is the sound of someone else munching chips really annoying?

OK. This is a serious question and I believe the roots are to be found in evolutionary biology. Through observation and experiment, I have determined that having someone else in the house – say a husband for example – munching on potato chips is really annoying. You wanted those chips, you knew they were there, you were saving them for a dry season – and someone else is eating them up. Is this the reason it is so annoying or is there something else going on? Help me out here.