You Can't Fool Your Pets, They Know When You're Late

Analysis by Dr. Karen Shaw Becker

Story at-a-glance -

  • New research has identified previously unknown neurons that appear to help animals keep track of time
  • In an experiment, these timing cells turned on in mice as soon as they stopped running and started waiting
  • This discovery opens the door for future studies in other mammals, as well as neurodegenerative diseases in humans
  • Dogs may be able to tell time in a variety of ways, including using their extraordinary sense of smell

Many of us with furry family members are pretty much convinced our pets can somehow tell time. Otherwise, how do they know to expect us home at a certain hour? How do they know it's mealtime, or bedtime, or time for a walk? We never catch them checking the clock, so how do they know these things?

Researchers Discover Previously Unknown Set of Neurons That Keep Time When an Animal Is Waiting

A new study conducted at Northwestern University and published in the journal Nature Neuroscience suggests researchers have found the best evidence to date that animals actually can judge time.1

"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," study leader Daniel Dombeck, Ph.D. stated in Northwestern press release. "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."2

Dombeck and his colleague, James Heys, Ph.D. have discovered a previously unknown set of neurons in the medial entorhinal cortex of the brain that turn on like a clock when an animal is waiting. The medial entorhinal cortex is located in the brain's temporal lobe and is associated with memory and navigation.

Since that part of the brain "encodes spatial information in episodic memories," the researchers theorized it might also be responsible for encoding time. They designed an experiment with mice called the virtual doorstop task in which a mouse runs on a real treadmill in a virtual reality environment. The mouse is trained to run down a virtual hallway to a virtual door located about halfway down the hallway.

The mouse stops at the door, and after six seconds, it opens and he's able to continue down the hallway to receive a treat. After several trial runs down the virtual hallway, the researchers made the door invisible. The mice still stopped at the location of the now nonexistent door, cued by the floor texture change at that spot, and believe it or not, they waited six seconds for the "door" to "open" and then made a mad dash to the end of the hallway for their reward.

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

'Timing Cells' Clicked on When the Mice Stopped Running

The researchers took high-resolution images of the mice's brain activity during the experiment and were able to actually watch their neurons fire.

"As the animals run along the track and get to the invisible door, we see the cells firing that control spatial encoding," explains Dombeck. "Then, when the animal stops at the door, we see those cells turned off and a new set of cells turn on. This was a big surprise and a new discovery."

The new set of "timing cells" didn't fire while the mice were running, only when they were resting during their six second wait at the door. "Not only are the cells active during rest," Dombeck said, "but they actually encode how much time the animal has been resting."

Newly Discovered Neurons Open the Door to Future Studies

If you're wondering how the brains of mice are related to your dog's or cat's brain, simply put, there are many similarities among mammalian species in the ways in which our nervous systems function, which is why research into one species often lends insights into other species.

In fact, the discovery of these new time-encoding neurons in mice will help scientists study the effect of neurodegenerative diseases on this set of cells in humans. According to Heys:

"Patients with Alzheimer's disease notably forget when things happened in time. Perhaps this is because they are losing some of the basic functions of the entorhinal cortex, which is one of the first brain regions affected by the disease."

Dombeck adds:

" … [T]his could lead to new early-detection tests for Alzheimer's. We could start asking people to judge how much time has elapsed or ask them to navigate a virtual reality environment — essentially having a human do a 'doorstop' task."

How Else Do Dogs Tell Time?

While the Northwestern study suggests the brains of mice are able to measure time intervals, further research is required to determine if the same or a similar system is functioning in the brains of other species. In addition, if dogs also have "timing cells," it would be interesting to learn how accurate their timekeeping is. It would also be fascinating to understand more about how dogs' amazing noses help them "smell" time: