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WHEN WE ARE children, short time periods represent a much larger chunk of our lives so far, compared with when we are older. This may lead a 5-year-old to feel that a year is an intolerable time to wait for Christmas, while for an adult, those 365 days fly by.

to our puzzling contractions of time than that. Some of it is in the brain. Adrian Bejan at Duke University in North Carolina says the brain’s processing speed slows as we age – caused by the greater complexity of our neural networks that means signals travel greater distances. Our ageing brain captures less information per second, so packs less temporal information into one block of time, or “episode” (see “How do we sense time?”). This can create the illusion that time has sped up. When we are younger, experiencing things for the first time may pack more into each episode. Like a slow-motion camera capturing thousands of images per second, it crams more into each time period and your subjective experience is of time passing more slowly.

Moment to moment, our emotional state can affect how we perceive time passing, too. It seems to fly when you are having fun and drags when you are bored. This may be to do with how our body processes time. The theory of “embodied cognition” says it is the processing of physical sensations that creates our perception of the world around us, including our sense of time. The body has numerous rhythms, after all – from the beating of the heart to the hunger in our stomach – that might all give the brain a sense of how much time has passed.

We know that the brain integrates our bodily signals in a region known as the insula, located deep in the brain between the frontal and temporal lobes. This is essential for our sense of self and the construction of conscious experience, which must include some sense of time passing.

, at the Institute for Frontier Areas in Psychology and Mental Health in Freiburg, Germany, asked people to replicate the length of high-pitched tones while he measured their neural activity in an fMRI scanner. During this task, participants showed more heightened activity in the insula than when they did a control task in which they pressed a button as soon as the tone had stopped. It looked like they were using their bodies’ signals to gauge how much time had passed.

According to this idea, anything that directs more attention to our bodies should make time seem to slow. This might explain why time crawls when we are hungry or cold. “If you don’t have distraction, you start attending to your bodily self,” says Wittmann, “and time drags.” If you focus your attention on something else, you are no longer listening so intently to those bodily signals, and time seems to speed up.