As we look more closely at our perception and thinking, we may find that we are quite often “somewhere else”. We may be physically sitting in the room, walking down the street, or lying in bed, but in our minds we are wandering around in time and space: we remember a situation of yesterday or last year and replay it like a movie, we imagine ourselves in a situation tomorrow or in 10 years, and wonder or worry about all sorts of situations that have nothing to do with our perception in the here-and-now.

Scientists call this behavior of our mind “mental time travel”. Why do we have this behavior? Can other species do that too? Why, or why not? None of us can remember our first birthday. But if you are old enough to read this text, then mental time travel probably determines much of your everyday experience, sometimes in a negative way, and sometimes in a positive way. How and when do we develop this behavior in the course of our lives?

While these questions are still being debated, most scientists who study these issues believe that mental time travel has become particularly elaborated in our species. Moreover, we are not born with it- children from the age of about 4 years are increasingly beginning to have ideas about the past and the future and to include them in their actions. Today, thanks to stories, historic documents, calendars, science and other cultural knowledge we have a concept of and can imagine a past tens, thousands, millions or even billions of years ago, and we can imagine and prepare decades into a forseeable future. Relationships with other people, language and cultural knowledge are seemingly important factors that play a role in the development of these abilities for mental time travel.