My boyfriend and I went to New York on Saturday night to see Billy Joel, and we left our dog Henry with his grandparents. We missed him. We saw people walking dogs and reminisced on our walks with Henry. We discussed how much he would despise the city due to his hatred of crowds. When we returned home to retrieve him, he barely looked at us. He was furious with us for leaving him, and although I can count on one hand how many times I have left him overnight in three years, the damage was done. With a broken heart, I wondered, how long does he think we were gone? Since measuring time in seconds, minutes, and hours is a human invention, do dogs understand time?
Yes and no. While there is no scientific evidence to prove how much time they can grasp, if your dog heads to his food bowl at 5 P.M. or cries by the door when your spouse is expected home, it’s hard to deny she knows something about time.
How can dogs tell time?
Biologically. Dogs, like us, have circadian rhythms, a 24-hour cycle that regulates bodily processes and tells them when to sleep and eat. The brain coordinates how a dog responds to these circadian rhythms, and a dog’s biological clock – the internal system that controls his everyday activities – allows him to recognize things like sunlight and nightfall and helps him associate certain behaviors, like going outside or eating, with those times of day.
Environmentally. Dogs are smart – they pick up on environmental cues like scents, feelings, and sounds around them to perceive the situation and figure out what’s happening or about to happen. When my dog sees me put on makeup, he knows I’m about to leave the house. When he hears my boyfriend zip his jacket, he knows his evening walk is about to commence. Although I never been gone from him for more than one day, I assume he would react strongly upon my return. Dogs remember their owners — whether it’s been one day since they’ve seen them or three years — because of their strong sense of smell and facial recognition. When I watch videos of soldiers returning from war, I get teary-eyed watching their dogs greet them after months or years of not seeing them. But while I do believe the dog knows he has not seen his owner for a long time, I also believe the dog picks up on cues around him – the soldier’s excitement to see the dog and the soldier’s family’s excitement – intensifying the dog’s greeting and making him jump, wiggle, and cry in his owner’s arms.
Physically. Dogs’ sense of smell is uncanny. They can smell how long you’ve been gone, and if you have the same routine every day, they can deduce how long it will be until you return. They can also tell time by paying attention to their hunger pangs or need to go to the bathroom. Although they may not know exactly how long it’s been since their last meal or their last walk, their bodies can tell them it wasn’t recent.
How do dogs perceive time?
According to a study done by Therese Rehn and Linda Keeling, dogs greeted their owners more intensely after being left alone for two hours compared to being left alone for thirty minutes. However, there was no difference in greeting between two hours and four hours left alone, which suggests that anything beyond two hours is unclear and needs more research. Studying animals – for example, how they perceive time and the way they form memory – not only helps scientists learn more about animals, it helps them learn more about humans and how our brains work compared to animals.
When long-term memory is studied in humans, it’s often broken down into two categories: declarative memory and implicit memory. Declarative memories are personal stories and experiences that we have stored, whether it’s the day we graduated college or the day our child was born. Implicit memories are unconscious or automatic muscle memories that are used to complete tasks that we have learned and repeated over and over again, like driving a car or brushing our teeth. And while there is still uncertainty and under-researched proof that dogs have declarative memories, if you’ve ever trained a dog or seen one "sit" or "stay" years after they learned how, it’s pretty clear that they possess some form of implicit memories.
Another type of memory that humans and some animals possess is episodic memory – the ability to recall what, where, and when pasts events occurred. Chimps and orangutans perform well when tested for episodic memory, but the verdict is still out on dogs because dogs have been disregarded when it comes to testing and lab research. Since dogs are domesticated, scientists didn’t think they could prove anything about how natural species behaved and have only really begun studying them in the last 15 years.
While we do know dogs have some form of memories, their episodic memories are not strong. It’s like they learn something and remember it through repetition without remembering why they know it. I experienced this with my dog: Henry got into a fight at the dog park almost two years ago. Before that fight, he loved all dogs – he ran up to them, played with them, and annoyed the crap out them. But since that fight, he is skittish around dogs, and we have to ease him into meeting them so he doesn’t get scared or turn aggressive. With my episodic memory, I remember that fight like it was yesterday: I remember which park we were at (Seger Park in Philadelphia), what kind of dog he fought (a bulldog), and which bandana he donned (his American flag bandana). But since Henry doesn’t have episodic memories and can’t remember specifics about that day, he only knows he is more wary of dogs – all dogs – than he used to be and that he doesn’t want or need to greet them like he used to, but he doesn’t know why.
Although a dog’s perception of time is widely under-researched, and there is much left to uncover, it’s nice knowing that dogs do miss us when we’re gone. It’s also pretty cool knowing that dogs live in the moment and don’t hold grudges because life really is too short. In fact, humans should live more like dogs. We should put down our phones and enjoy time spent with each other - whether minutes or days - and focus less on the past and mistakes we’ve made. My dog doesn’t remember if I was mad at him last week - let alone why - and it’d be nice to take a page from his book and live more honestly.
Image: Y Nakanishi