Do animals know how long a second is, or how much time has passed? That’s a bit of an open question, but we may be slightly closer to an answer.

A study published in the journal Nature Neuroscience suggests the strongest evidence yet that animals may indeed be able to judge the passage of time. The research was conducted by Daniel Dombeck and James Heys from Northwestern University in Illinois.

"Does your dog know that it took you twice as long to get its food as it took yesterday? There wasn't a good answer for that before," Dombeck said in a statement. "This is one of the most convincing experiments to show that animals really do have an explicit representation of time in their brains when they are challenged to measure a time interval."

To make their findings, the researchers placed a mouse on a physical treadmill in front of a virtual reality screen. To earn a reward, the mouse was required to run down a virtual hallway, wait at a virtual door for six seconds until it opened, and then pass through it. This was called the virtual “door stop” task.

However, once the mouse was used to this scenario, the researchers made the door invisible but kept textures on the floor so the mouse still knew where the door was. And, when the mouse ran down the hallway, it still waited for six seconds outside the door – even though it wasn’t there.

"The important point here is that the mouse doesn't know when the door is open or closed because it's invisible," said Heys. "The only way he can solve this task efficiently is by using his brain's internal sense of time."

Dombeck and Heys focused on a region of the brain known as the medial entorhinal cortex for the experiment, which is associated with memory and navigation. And by imaging the mouse’s brain activity, the team were able to watch the neurons fire in its brain.

This showed them that when the mouse ran down the track, it’s cells that controlled special encoding fired. But when it stopped at the door, those cells turned off and new cells turned on, which Dombeck said was “a big surprise and a new discovery.”

This has broader implications too, such as studying Alzheimer’s disease. It may be that people with the disease are losing basic functions in their entorhinal cortex, which could affect their memory and their sense of time.