When a cat sleeps with its paws twitching and its eyes moving rapidly back and forth, it may seem like it is imagining chasing after a mouse. Similarly, when a dog makes low-pitched whimpers and growls while sleeping, it may appear as if it is dreaming. However, understanding the nature of dreams in animals like dogs and cats presents a challenge for researchers. Unlike humans, animals lack the capacity for language, which makes it difficult for them to communicate their experiences or sensations while asleep.
There is evidence that suggests mammals and possibly birds also experience dreaming. However, the absence of language in animals poses a barrier to directly understanding their dream experiences. Researchers cannot communicate with animals during their dreams, making it challenging to gain insight into what it is like for a dog or cat to dream.
Does Dreaming Happen During REM?
It is widely accepted that the stage of sleep known as REM (Rapid Eye Movement) sleep, during which humans have their most vivid dreams, is also observed in almost all mammalian species during their sleep. During REM sleep, the majority of voluntary muscles in the body are paralyzed, except for the eyeballs that move rapidly back and forth behind closed eyelids. The brain remains highly active, exhibiting faster and more complex patterns of brain waves compared to deep sleep.
In dogs, cats, and gorillas, REM sleep accounts for approximately ten to twenty-five percent of their total sleep time, which is similar in duration to the stages of sleep experienced by humans. However, the question remains: Do they dream in the same way that we do? Considering the process of evolution, it is highly likely that the capacity to dream existed before the existence of humans. However, providing concrete evidence to support this hypothesis remains a challenge.
Cats That Are Fast Asleep Due to Hunting Fever
In the 1960s, Michel Jouvet, a sleep researcher from France, conducted a controversial experiment that attracted attention. He successfully reversed the muscle paralysis that typically occurs during REM sleep in cats. Initially, the cats fell asleep normally, but when they entered REM sleep, their typical behaviors ceased. Instead, they exhibited behaviors such as bucking, hissing, rushing around the cage, and their fur became bristled. The experimenters were astonished by the extreme and bizarre behavior displayed by the sleeping animals.
The observed behaviors in the cats implied that they were engaged in combat or on the hunt for an unseen adversary. Remarkably, throughout these behaviors, the cats remained in a deep sleep, completely unresponsive to bright flashes of light or enticing scents of freshly cooked food. Jouvet interpreted these findings as evidence that cats, and potentially other animals, have the ability to recreate familiar situations in their dreams, similar to humans.
Do Rats Walk in Labyrinths in REM Sleep?
Another method employed to study animal dreams involves comparing the brain activity during REM sleep with the activity observed during a specific activity performed earlier while the animals were awake. In 2001, a study conducted by Kenway Louie and Matthew Wilson of the Massachusetts Institute of Technology focused on rats. The rats were trained to navigate a labyrinth successfully, and electroencephalography (EEG) was used to record their brain waves during this learning phase as well as during subsequent REM sleep.
Upon comparing the EEG recordings, the researchers discovered significant similarities between the two, suggesting the reactivation of episodic memory traces during REM sleep. These findings provide strong indications that mammals, like humans, tend to replay their daily experiences in their dreams. While verbal confirmation of an animal’s dream experience is not possible, doubts may persist, and the awareness of dreams in animals remains an unanswered question.
