A whole lot of our communication is non-verbal. When we are having a heated discussion, the non-verbal stuff actually blocks the real message getting through. This is often why the argument goes around in circles without getting resolved: because the real message isn't getting through.
Amy gives a hack for either type of non-verbal communication style - both body language, and tone, which can be applied in any relationship to trump the non-verbal stuff and allow the real message to get through.