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Can Animals Time Travel?

Have you ever looked into your pet’s eyes and wondered what is going on inside their head? If they really love you? If they can recall your past adventures together? You’re not alone! One of the biggest questions about nonhuman animals’ minds is whether they can have complex thoughts like humans do. Unfortunately, we are not able to simply ask them yet. 

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Instead, we analyze human memory and do experiments on nonhuman animals to try and see if or how their memory ability differs from ours. In humans, memory is categorized into two types of long-term memory stores: declarative and non-declarative. Non-declarative memory consists of long-term memory that we are not consciously aware of, such as how to ride a bike. It is generally accepted that animals have non-declarative memory.  Animals develop all kinds of skills, even including riding skateboards!

Declarative memory consists of conscious memories: semantic memory (general knowledge and facts) as well as episodic memory (memory of unique, personal events that include “who, what, where, when”). Humans use semantic memory to know that dogs are mammals, or how to behave around a dog who is wagging their tail. Episodic memory is employed for remembering events, such as the first time you met your pet! Scientifically, the difference between declarative and non-declarative memory is that declarative memory is processed through the amygdala, a specific part of the brain, whereas non-declarative memory is not. 

For scientists to confirm the existence of non-declarative memory in nonhuman animals, they adapted experiments meant for humans. For example, a human test for measuring non-declarative memory can be adapted to animals by using a dog who reacts correctly to “sit,” “lay down,” “stand,” and “bark” hand signals. The experimenter may give these cues to the dog in what the dog thinks is random order, but actually is a pattern. As the dog practices and learns the pattern, the cue response time gets shorter, showing the presence of non-declarative, skill-learning memory. It has also been accepted that most animals have semantic memory. Chimpanzees, for example, memorize words, or dogs associate commands with actions. The question that begs to be asked is whether or not nonhuman animals use episodic memory? Can they travel through time through their thoughts like we can, or are they stuck in the present?

Some researchers claim that it is impossible for other animals to have episodic memory because “verbal competence” (ability to use language with the experimenters) is required and is a prerequisite to determine the presence of episodic memory. They argue that since the term “episodic memory” was developed for humans, it cannot be used by animals of other species. If your sibling had an outfit tailored to their body and argued that it wouldn’t fit you simply because it was originally created for them, does that mean that the outfit would certainly not fit you?  Couldn’t there still be a possibility of it fitting even if it was not designed for you?

Some researchers also think that nonhuman animals can recall the facts of a past event but that the researchers cannot conclude if it is a personal memory or a “replay” of the memory. This definitely saddens most pet owners, who are unsure if their pet recalls the same happy memories that they do. William Roberts debates that unless animals feel the need for a reward or have an innate behavior for it, they cannot prepare for future tasks related to that reward. This means that they can only live in the present and solve problems without past recollections. However, has your dog ever accidentally peed on your carpet while you aren’t home and might have even prepared for you to see it by hiding in a certain spot or hiding toys they think you might remove as punishment? 

How can we actually know whether or not animals have episodic memory? We first have to set a specific part of episodic memory to test, such as item-context recall or simple communication about events. We can’t simply ask animals to recall a certain event, so we have to create unique experiments or alternative ways to communicate.

Item/Behavior-Context Recall

I wonder if animals can “replay” a memory from start to finish? A study done by Claudia Fugazzi looks at this question using item-context recall. She developed her study around the idea that recalling an incidental memory, something that was not remembered on purpose or consciously, relies on episodic memory. This study mimics the memory we use if a friend asks you if you passed by a certain store on your way to their house and if it was closed or open. Since you were not consciously looking to remember whether or not the store was there, you would have to use your episodic memory to actively recall the drive and the details of the store. Fugazzi had a group of people teach dogs to copy their movements with an umbrella (e.g., one leg up and one paw on the umbrella). Then, once the dog learned that they had to copy movements, the researchers moved the dog to a different context (a blue mat rather than grass) and did similar poses with the umbrella, but instead of signaling for the dog to copy the pose, they taught the dog to lie down when instructed with a different hand gesture. During this exercise, the dog did not need to respond to the specific poses or even pay attention to them as before, they just had to lie down after the pose. Once the dog mastered this new trick, the trainer changed it up and did a pose like normal, but when the dog expected to get a signal to lie down, the trainer gave them the signal to copy the pose. The dogs had to go back into their memory and replay the pose that they just saw in order to copy it since previously they did not pay attention to the pose itself as they did not expect to have to copy the pose. 

Woman Demonstrating Task to Dog, Dog Replicating It

Can animals recall “what, when, and where” memories like humans can?  A study on mice led by Danielle Panoz-Brown showed that mice recall specific events and the context in which those events occurred. The researchers taught the mice that in each context (differently designed areas), they are provided with two scents to choose from–one they saw earlier in the day or a new one. The mice were rewarded with a treat if they went to the new one but given nothing if they chose the old scent. They exposed the mice to, for example, a blueberry scent in a black and white checkerboard room, then a blueberry and rose scent in a pink room with the rose scent being last. Then the scientists had them moved back to the checkerboard room to choose between rose or blueberry scents to decide which was new for that room. Even though the mice were more familiar with the rose scent since they had smelled it more recently than the blueberry scent, they were able to recall the previous room and what scent they smelled in that context in order to choose the new scent! If the mice had chosen the blueberry scent, it would indicate that the mice relied on their familiarity, and chose to not pick the scent they most recently smelled, regardless of context. The researchers concluded that mice could remember multiple unique events and the contexts in which these events occurred using episodic memory! This showed that nonhuman animals could have the ability to recall–going back in time to remember what happened at a specific place, rather than just being familiar–the strength of the signal from their brain indicating if they had contact with the scent recently. These mice were able to recall where, what, and when with ease!

Simple Thought Communication

Can nonhuman animals remember signs for things, and use signs to communicate complex thoughts about events? A particularly heart-warming study was done by the Gardners, who decided that for more research to be done on Chimpanzees and their level of understanding and thought, they had to learn to communicate with them. They decided to raise a Chimpanzee, Washoe, in their home as their own child and teach her American Sign Language (ASL). Amazingly, Washoe communicated with humans and even was able to recognize herself in a mirror. After her early years, the Gardners moved her to a primate research program, and Washoe was slowly introduced to other signing Chimpanzees! The Gardners raised four other Chimpanzees to use sign language, and they all became a sort of family. They communicated to each other using signed words even when no humans were present, meaning they weren’t simply copying the humans or looking for cues! Washoe had a baby and was the first-ever nonhuman documented to teach human language to another nonhuman on their own! The family not only went on to provide evidence for the existence of episodic memory in animals, but the Gardners showed that animals are capable of so much more than people give them credit for. 

The incredible Chimpanzees were video recorded, and their signs were then studied. It was shown that they were able to mention objects that were not even in the room with them. Washoe disproved some scientists that believed animals only communicated about their present needs when researchers found that when the Chimpanzees talked about food (5% of their signs used), it was mainly to talk about the concept of food without seeing or eating it. This shows that they are able to recall past good experiences with food and communicate it to their peers and supports episodic memory! Similar research still needs to be done on animals less closely related to humans, but rest assured that your pets might be able to have nice conversations about how much they hate dry kibble and want more treats instead.

There are also a few examples of this Chimpanzee family communicating about events that happened long ago in anticipation of it happening again. For example, the researchers would decorate and give the Chimpanzees a tree covered with treats for them on Christmas. One year once it started snowing, one of the Chimpanzees signed “Candy tree,” which was what they called the treat tree. This signals their understanding of time, as well as their ability to remember their positive experience with the candy tree. Another instance of this type of memory was when, after an 11-year absence, the Gardners saw Washoe again. Washoe stared at them, confused, but signed their names. Washoe then went up to them and began to play a game she last played when she was 5 years old. She was able to put together the memory of the Gardners with her experience playing the game and seeing the Gardners reminded her of the game. Hopefully, after more research, it will be confirmed that even if you can’t see your pets for a while, they can still remember you and the things you did together!


Episodic memory has various definitions besides the general understanding of recalling detailed past events. Episodic memory could be said to occur during the activation and inhibition of specific regions of the brain. It could be defined by self-awareness or planning. Some scientists don’t support the idea that animals have episodic memory because it doesn’t completely coincide with human episodic memory. However, these are different species and have different ways of doing things. Cuttlefish don’t even have a hippocampus but have still shown episodic memory! Rather than using human episodic memory to define general episodic memory in animals, there should be more simplistic features to define animal episodic memory (e.g., remembering what, where, when, etc.) This would shift the researchers’ focus from looking for human memory characteristics in animals, anthropomorphizing them, to figuring out how animals might have their own way of expressing episodic memory. While the field is always changing, what do you think, do animals have episodic memory? Can they travel through time? For now, you can take comfort in the fact that your dog most likely can recall past positive interactions with you!

References

Cavalieri, Paola and Peter Singer. “The Great Ape Project—and Beyond”, in The Great Ape Project, New York, St. Martin’s Press, 1993, pp. 304–3.” 12.

Christie, M. A. “A New Rat Model of the Human Serial Reaction Time Task: Contrasting Effects of Caudate and Hippocampal Lesions.” Journal of Neuroscience, vol. 24, no. 5, 2004, pp. 1034–1039., https://doi.org/10.1523/jneurosci.3340-03.2004.

Fugazza, Claudia. “Recall of Others’ Actions after Incidental Encoding Reveals Episodic-like Memory in Dogs.” Current Biology, vol. 26, no. 23, 2016, pp. 3209–3213., https://doi.org/10.1016/j.cub.2016.09.057.

Gardner, R. Allen. “Review of sign language studies of cross-fostered Chimpanzees.” Journal of the Washington Academy of Sciences, vol. 93, no. 1, 2007, pp. 37–57, http://www.jstor.org/stable/24536251.

Schnell Alexandra K, Clayton Nicola S, Hanlon Roger T. and Jozet-Alves Christelle. “Episodic-like memory is preserved with age in cuttlefish.” Proc. R. Soc. B. 288:20211052 20211052, 2021, http://doi.org/10.1098/rspb.2021.1052

Roberts, William. “Are animals stuck I time?” Psychological Bullitin, vol. 128, no. 3, 2002, pp. 473-489, 10.1037/0033-2909.128.3.473

Squire, Larry. “Larry Squire – Declarative Memory in Humans and Animals.” Youtube, GoCognitive, 2012,https://www.youtube.com/watch?v=wkM35n70XjY.

Panoz-Brown, Danielle. “Rats Remember Items in Context Using Episodic Memory.” Current Biology, vol. 26, no. 20, 2016, pp. 2821–2826., https://doi.org/10.1016/j.cub.2016.08.023.

Memory
Animal Cognition | Episodic Memory

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