Time travel study shows my years take up more space than yours

We think about time in terms of space, as revealed in the way we talk about it ("looking ahead to our future"; "looking back at our past") and in the results from psychology experiments. For instance, people from countries that write right-to-left find it easier to associate future events with the right-hand side of space. This begs the question – how much space do we think time takes up, and is it always constant, or does it vary with how richly we represent particular episodes?

Brittany Christian and her colleagues have explored this question with a pair of fascinating studies. The first involved 60 participants (aged 18 to 32 years) marking the position of various birthdays on a 36cm horizontal line. The middle of the line was marked as "now". Some participants were asked to draw a mark to show the position of their 8th and 9th birthdays, their previous and next birthdays (relative to now), and their 58th and 59th birthdays, representing past, present and future periods of time, respectively. Other participants did the same for the equivalent birthdays of a best friend; others did it for a stranger who shared the same birth date as them.

The key result here was that participants indicating their own birthdays tended to leave a larger gap between their previous and next birthdays, as compared with participants who marked the birthdays of a best friend. In turn, those marking the birthdays of a best friend left a larger gap between previous and next birthdays than did participants who marked the birthday positions of a stranger. No contrasts emerged for gaps between birthdays in the further past or future (8th and 9th or 58th and 59th), perhaps because we represent such distant time more generically. The main result suggests that the more richly we encode past and future events in our minds, the more physical space we allocate to our mental representation of those periods.

A second study was similar but this time 63 participants (aged 18 to 32) controlled their passage backwards or forwards through time, an experience that was created using the optic flow of white dots on a computer screen. The contraction of the dots towards the centre creates the sensation of moving backwards, the expansion of dots outwards gives the feeling of travelling forwards. Using a keypad to control their motion, the participants were asked to move forward or backwards through time until they reached various birthdays up to ten years in the past or future. As in the first study, they did this either for their own birthdays, the birthdays of a friend, or a stranger.

Participants chose to travel through more space to reach birthday events in their own lives, compared with the space they travelled when journeying towards a friend's same birthdays. Participants traversed the least amount of space to reach those birthday dates in the life of a stranger. These differences were true for past events and future events, and they held across the full span of time that was investigated (i.e. a birthday up to ten years in the past or future).

Christian and her colleagues said their finding was consistent with construal level theory: "more space is allocated to events that feature self-relevant and episodically rich (i.e. more concrete) mental representations." Future research is needed to see if other factors also affect the amount of space allocated to temporal representations, such as factual knowledge or emotional salience. Would we allocate more space to time in the life of someone who we like but don't know well, or to someone we know well, but don't like?

The researchers said the "behavioural implications of these findings remains an important challenge for future". It's speculative for now, but they surmised that their results could help make sense of the planning fallacy – our tendency to underestimate how long things will take us, compared with others. The fact that we represent our own time with more space could tempt us to feel like we can get more done in a given period.

Further reading

Christian BM, Miles LK, and Macrae CN (2012). Your space or mine? Mapping self in time. PloS one, 7 (11) PMID: 23166617