By Christian Jarrett

We all have routes that are part of our daily lives, whether it’s the way to the local convenience store, school or the office. How does this deep familiarity affect the way our brains represent the space and our ability to move through it?

Based in part on what we’ve learned from studies of so-called “grid cells” in rats’ brains, Anna Jafarpour at the University of California, Berkeley and Hugo Spiers at University College London predicted that greater familiarity with an area would lead us to overestimate its physical extent – in essence, they thought a more detailed neural representation would make that space seem larger. In turn, they predicted that same detail would make us more likely to exaggerate the walking time to destinations reached through that familiar space.

In fact, while their new findings published in Hippocampus suggest spatial familiarity does indeed stretch our perception of the magnitude of physical distance, it has the opposite effect on our judgments of travel times through that space – that is, we underestimate how long it will take us to travel through highly familiar routes. It’s a mental quirk that might just provide us with a new excuse for why we’re so often running late.

Jafarpour and Spiers asked a group of young international students who’d been living in the same building – William Goodenough House – in the Bloomsbury area of London for nine months (don’t panic, this was pre-Brexit), to sketch a map of the area on a sheet of A4. They could take as long as they liked to complete their sketch.

The students – 13 men and 7 women – had walking experience in the area, but no driving experience. A to-scale image of the building was marked on their A4 sheet as a guide. The students had to sketch with the top of the sheet representing south – this was to stop them drawing a map from memory because, of course, maps always have north at the top.

Next, the students answered questions about walking time to different destinations in Bloomsbury from their building. Finally, they were shown a satellite map of the area and asked to mark routes they walked on a daily basis.

Looking at the way the students had sketched the areas of Bloomsbury with which they were most familiar (based on where they’d indicated they walked on a daily basis), it was apparent that they overestimated the physical extent of these routes – that is, they had drawn these areas too big compared with how they drew less familiar areas. In contrast, they underestimated the walking time of routes with which they were most familiar compared with less familiar.

This seems like a contradiction – the students expected to arrive sooner at destinations reached via familiar routes that their own sketches suggested were longer than less familiar routes. It’s a quirk that raises many interesting questions about how familiarity affects the brain’s representation of time and space.

The researchers discuss several possible explanations, including that there are separate neural systems for computing spatial extent and time-to-travel through that space. Related to this is the possibility that we judge the time-to-travel through familiar routes using our experience-based knowledge, whereas drawing a “south-is-up” map cannot be based on knowledge and must be freshly reconstructed from the brain’s spatial representation of the area.

These are fascinating questions for future research to address, but for now the everyday implication is that we are especially likely to underestimate the time it takes us to walk the routes with which we are most familiar – like to our school or office. Your new excuse for tardiness – “Sorry I’m late sir, my brain’s got a problem judging ETAs for familiar routes”.

—Familiarity expands space and contracts time

Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest