It’s five o’clock, and your dog is excitedly wagging her tail and nuzzling against you. Your furry friend is hungry and seems to know that this is the hour you usually feed her. But was this performance a simple reaction to a rumbling in Ginger's tummy or are canines actually able to somehow read the clock?

Anecdotally, many dog owners will tell you that their dogs seem to anticipate dinnertime or the hour when they regularly go on a walk. Some owners claim their dogs know these important times to within minutes, notifying them at precisely at 5 p.m. that a meal should be served, or maybe 4:49 or 5:01, occasionally 5:03, but virtually never more than 5 minutes earlier or later. It’s like the dog is reading a signal, maybe from the amount of daylight or perhaps some other sense, that tells him the time. But time is a human invention, at least in the way we normally think about it in terms of seconds, minutes, and hours. Can dogs, or other animals, actually understand time in the same way that we do?

What's Up With ThatEach week, we'll explain the science behind a strange phenomenon that you may be wondering about, or may be hearing about for the first time right here. If you've seen or heard of something you'd like us to explain, send us an email.

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Why You Always Seem to Choose the Slowest LineCognitive scientists are interested in the ways animals form memory, mostly because it helps us understand the way our own brains work. Researchers often break down our long-term memory into two categories. There’s implicit memory, an unconscious muscle memory that we use to perform tasks we have learned and repeated many times in the past, like tying a shoelace or riding a bike. And there’s declarative memory, where we store the personal experiences and factual information that make up the story of our lives.

Pavlov taught us that dogs and other animals have implicit memories, which are used for trial-and-error learning or conditioned responses. But there's still some uncertainty regarding whether or not non-human animals have declarative memory. Researchers are particularly interested to figure out if animals have what’s known as episodic memory, or the ability to recall contextual information about past events, such as what was happening, or where and when it occurred. Stewart described this ability to think about and re-experience the past as a type of mental time travel.

Scientists have studied episodic memories in apes, monkeys, rats, bees, and some birds, including crows. Many experiments have tried to determine if these species have a “www” memory or the ability to recall the basic facts about an event: what, where, and when. The outline of the test for each animal is fairly simple.

Let's say you give a chimpanzee two sealed opaque jars, each containing a treat. One jar has a non-perishing snack, something like a grape. But the other contains a treat that needs to be enjoyed within a certain time limit, like a frozen cube of juice that’s going to melt. After five minutes, the chimp is given the chance to open one jar. After an hour, it can open the other.

Once the test has been given several times, most creatures will crack open the jar containing the disappearing treat first. They have learned by experience if they wait too long, this one won’t be around anymore. They have demonstrated the three w’s. What: a tasty treat. Where: inside this jar. When: within five minutes or it won’t be around anymore.

Bonobos, chimps, and orangutans pass this test with flying colors; they seem to have this sort of episodic memory. There is also good evidence that crows and rats can create www-type memories. Rhesus monkeys, so far, have been shown to remember the what and where, but have some trouble with the when. And even bees seem to possess some type of episodic memory tied to their circadian rhythm.

While there is quite a bit of evidence to suggest that dogs remember people (like their owner) and events (like going to the park), it’s still an open question whether or not they can travel back in time in their minds. That’s because man’s best friend has sadly been neglected when it comes to lab experiments. For a long time, scientists thought that because dogs are domesticated, they couldn’t prove anything about how natural species behaved. It is really only within the last 15 years that extensive examination of the doggie mind has begun.

But for www memories, “there is very little if not no research when it comes to dogs,” said Stewart.

So can dogs tell time? Maybe, but we really don’t know. But there are some interesting ideas out there about how they may do it if they can. While making it clear that these aren't yet backed up by scientific evidence, Stewart suggested some hypotheses to explain your pet’s behavior at feeding time.

Dogs, like most mammals, have a circadian rhythm, an internal sense that tells them when to sleep or when to be active. Perhaps it’s their bodies, though not their minds, that can detect roughly what time it is. So if in the mid-afternoon your dog is used to getting her food, her body gets hungry around this time, and she starts getting excitedly all up in your business, demanding a bowl.

Another explanation could come from the fact that some animals can read environmental cues. Perhaps dogs use the length of shadows to know the time of day.

Some researchers have suggested that dogs are using their advanced sense of smell to sniff out how long it has been since some event happened. After you leave the house, your scent lingers, decaying slowly over the day. If you have a fairly regular schedule, it’s possible your dog has figured out that at the point when your smell has decreased by a specific amount, you’re going to unlock that front door (and he needs to get ready to come charging up to greet you).

In the video above, you can see an experiment where researchers fooled a dog by spreading his owners scent around the house, leaving the canine puzzled when the owner came home at his usual hour. While it doesn’t prove that dogs can smell time, it’s an intriguing idea.

Though there isn’t a good answer yet as to whether or not your dog knows what time it is, there could be one within the next few years. Dogs are receiving more and more attention from scientists, and it’s almost certainly only a matter of time before they are tested for www memories. Cognitive scientists in particular are interested to find the roots of our own episodic memory abilities.