We often think of the abstract idea of time in the concrete terms of space, saying we are “looking forward to the weekend” or “putting the past behind us.” These adages may be more than just metaphors. A study published in January in Psychological Science suggests that thinking of space may be a necessity to conceptualize time. When people's minds are not able to accurately understand space, researchers found, they have difficulty with time as well.

People with a condition called left hemispatial neglect ignore the left side of space—not remembering the left half of a scene or even not eating off the left half of their plate—after an injury or stroke in their brain's right inferior parietal lobe. In the new study, researchers investigated these patients' understanding of time. Because people who speak languages written left to right, such as English or French, tend to think of timelines with the past to the left and the future to the right, the team focused on how left hemispatial neglect might alter the left side of their mental chronology—that is, their thinking about the past.

Seven French speakers with hemispatial neglect, seven stroke patients without neglect and seven healthy people participated in a simple memory study. They learned facts about a fictional 40-year-old man named David—some of which were true of him 10 years in the past and some of which would be true 10 years in the future. They were then asked to remember as many of the facts as they could and to say whether they were true of David at age 30 or age 50. Sure enough, the people who have hemispatial neglect were worse than the others at remembering facts from the past—but not from the future.

When patients with this type of brain damage draw a face, says psychologist Lera Boroditsky of the University of California, San Diego, who led the study, they might depict only the right eye and ear, or they might cluster all the face's features on the right side. With memory, she notes, “we see a mix of those: to some extent, people weren't good at remembering things that were associated with the past, and the other error people made was misremembering things that were associated with the past as though they were associated with the future.”

When someone's internal understanding of space is thrown off, it seems, their corresponding ordering of time is disrupted. Boroditsky is planning to repeat the study with Hebrew or Arabic speakers, who read—and plot timelines—from right to left, to see if they neglect the future instead of the past.