Why AND and OR cause confusion

Like many online services, MasterVision lets users create searches which include ANDs and ORs.

These terms are used in everyday English, and so it’s easy to assume that their meaning should be clear.

But in practice, they can often cause confusion, and are sometimes the source of search results which don’t match up with users’ expectations.

So why is this? It’s all a question of context. Consider the following:

• apples AND oranges AND bananas

…versus:

• apples OR oranges OR bananas

On a shopping list, the first AND case would result in more items in your supermarket basket than the second. But in an online search, that same first case would result in less matching search results than the second with ORs.

The key to understanding the difference is that when searching, the terms all apply at single item level. So, a single item needs to match all of the AND terms to be a ‘hit’, but only one of the OR terms.

Applying the same logic in the supermarket, the first AND case might match a mixed fruit smoothie, but nothing in the fruit & veg aisle.

All of which illustrates, if further evidence was needed, that things aren’t always as simple as they seem. And I haven’t even mentioned NOTs yet…