Mr. Ranganath, how much of our conversation will I have forgotten after an hour? You will quickly forget most of it. As everyday life goes on, you will soon remember two or three key statements – and otherwise just the fact that we even talked. Our brains are constantly prioritizing what’s important. It makes us forget what is unimportant.

How does it know what is important? This is called an “educated guess” in English. It is the assumption that something is of interest or might be in the future: things that cause fear or pleasure. Things that surprise us. The brain retains what it thinks is surprising, what is motivating, what is important for survival – and what is new.

Many people understand our memory as precise storage – a mistake? The human brain is not a memory machine, but a thinking machine. There are studies that show that we forget about 60 percent of what we experience within two hours. On top of that, the memory does not replay experiences exactly as they happened. It’s not a recorder. But memories are incredibly important: they are the source we need to give meaning to the present and the future.

Sounds philosophical – what does that mean in concrete terms? All the decisions we make in the present are based on memories. These are processes that we are not consciously aware of. A simple example is the question: Where are we going to eat today? Our brain thinks: There was this great restaurant. But wait, my food wasn’t that good last time. Then the brain adjusts the decision based on that memory.

How? Maybe when you look at the menu you decide to order something else. Similarly, if a business partner lies to me, my future decisions will be based on the memory: He is a liar.

But we also store very specific technical knowledge. You know, people often complain to me that they are so forgetful in everyday life. I think their concerns about this are a big misunderstanding.

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