Theory 56/Blushing/Threshold lens
Visibility Is a Skin Ratio
The claim
A blush becomes visible above a threshold in the ratio of vasodilation to skin thickness, so the same response is obvious in one person and invisible in another.
01Mechanism
Colour depends on blood volume near the surface relative to the tissue covering it; the ratio sets visibility.
02Prediction
Visibility should track the ratio.
03Refutation
Visibility tracking vasodilation would remove skin thickness.