I imagine it's the same way they measure scoville units. It's sensitivity. How much of the substance is required for a group of people to consistently correct

I imagine it's the same way they measure scoville units. It's sensitivity. How much of the substance is required for a group of people to consistently correctly guess which of two identical water glasses have been spiked with the substance. If it's like this then 1/3000 is required compared to sugar.