The history

Jakob’s LawJakob’s lawBreak the pattern only when you can say why.Open the law → says people spend most of their time on other sites, and therefore expect yours to work like the others. It is the only law here that treats habit as habit, and not as a property of the brain.

Except that “the other sites” is a population, not a constant. Someone who came to the internet through WhatsApp has a different “other sites” from someone who came through Orkut. Someone using WeChat in China has another. Someone who reads right to left has another. Someone who went digital at seventy, inside their bank’s app, has a repertoire of two screens — and both are the bank’s.

The shopping cart sits in the top right corner because somebody decided that in the 1990s and the world copied it. There is nothing in the human brain asking for the right corner. There are thirty years of people seeing the cart there.

The mere-exposure effectMere-exposure effectRepeat the pattern until it becomes comfort and stop before it becomes irritation.Open the law → says we prefer what we have already seen, even without remembering having seen it. It is a law about perception which, up close, is a law about biography: it does not say what pleases, it says that what has passed through here pleases.

The availability heuristicAvailability heuristicFix the worst case before the average case: it is the vivid that stays in memory.Open the law → does the same to judgement. The vivid case weighs more than the average — and which case is vivid depends on what your country’s news repeated last month. The risk a Brazilian overestimates is not the one a Japanese person overestimates.

What to do is not to abandon the pattern. It is to know which pattern you are using and whose it is. When you follow the convention, you are betting that your user saw the same screens you did. Sometimes that is an excellent bet. Sometimes you are designing for your own browsing history.

PS: if your product serves people who have just arrived on the internet, Jakob’s Law is not merely less useful. It may be telling you the opposite of what you need to do.