A cup of traditional English tea.

A cup of traditional English tea. Photo: Supplied

Q When making a cup of tea, do we pour the milk or the tea first?

A In Gulliver's Travels, there was conflict over whether an egg should be cracked at the big or the little end, and today we still cannot agree whether to pour the milk or the tea first.

Science cannot say what taste you prefer, but it can suggest whether you can spot the difference. Are we really able to sniff the aroma, swish the brew around and tell which went in first?

Camellia sinensis is the basis of the most popular drink in the world, after water. The complex flavours come from intimidating-sounding compounds such as phenols, flavonoids, isoflavones and terpenes, and the bitterness comes from catechin. Milk contains casein, which binds to the catechins and reduces the bitterness.

The first thing that happens when hot tea is mixed with cold milk is that both change in temperature - the tea cools and the milk warms slightly. Overall, the effect is minor.

The heat affects the milk proteins, but the real test is, can you tell?

This is where the scientific method kicks in, and we can undo the human propensity for preconceptions, assumptions and outright bias.

It's also hard work because there are so many ways we can accidentally affect the results. You can read an example of a good experiment on the web by Tom Stafford. It was a ''double blind'', so neither party knew which cup was which.

This is to avoid traps such as the classic Clever Hans, the horse that seemed to be able to count.

Hans was certainly clever, but it turned out he was watching the body language of his owner, and really had no idea about five plus two.

So can you reliably detect milk-pouring violations? The subjects of Stafford's experiments could not.

Response by Rod Taylor, Fuzzy Logic
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