How do you make a mood necklace work?

Mood rings/necklaces DO NOT have any scientific meaning whatsoever. Yet, they do (mostly) tell the true mood of the wearer. the cause? Heat. Not just that, though. the lower quality ones will simply change color if you even breathe on it. The decent/high quality rings/necklaces change colors according to heat, just like the low quality ones. the reason it will reflect the true mood of the wearer (most of the time) is because of the way that your body heat fluctuates according to your mood. German mood rings, however are both more expensive and have a better chance at telling your true mood.