Watches might keep time in an absolute manner, but people don’t. Each person perceives time differently depending on mood, and moreover this perception changes with age. “When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That’s relativity,” Einstein famously said. Apparently, time slows down even when white folks are concerned not to appear racially biased, according to a study published in  Psychological Science.

“An example of time slowing is the experience that a full second has transpired after only half a second, which makes the duration of an actual second feel longer or slower,” the researchers explained. “The implications of a time-slowing bias for interpersonal interactions are profound—imagine a police officer needing to gauge the time in which a minority suspect must respond before force is exerted. The perceived difference of a half second could determine whether shots are fired.”

The Lehigh University in Pennsylvania researchers recruited 24 women and 16 men  The volunteers were first asked to fill a survey which measured whether or not they were motivated to control their racial bias. Then they were put in front of a computer screen where a geometric shape was displayed, followed by either a black face or a white face. Both faces had neutral expressions. The first image was shown for exactly 600 milliseconds, while the second was displayed for some time between 300 and 1200 milliseconds. Participants then simply had to state whether they thought the second image showed up for more or less time than the first one.

The researchers found that short amounts of time were mistaken for longer ones when participants who were motivated to reduce bias viewed black faces. However, the effect was noticed in those participants who didn’t care whether or not they seemed racist. The findings were confirmed by a second set of experiments involved 36 white males, but which followed a slightly different procedure.

“Ironically, people trying to suppress the appearance of bias are most likely to display this form of implicit bias because their motivation to control prejudice induces race-related arousal,” Moskowitz and his colleagues wrote.

How mood changes our perception of time

This study is only one in a growing of evidence that suggests our psychological and emotional states influence the passage of time. When we are sad and depressed, we feel that time passes more slowly. Every hour seems like an eternity. On the opposite end of the spectrum, fear causes time to fly. These findings were confirmed by a study which asked participants to watch three films which each elicited a different mood: sad, neutral or frightened. Apparently, the neutral and sad movies didn’t cause a change in time perception but  “the selective lengthening effect after watching frightening films was mediated by an effect of arousal on the speed of the internal clock.”