According to researchers at the University of Tubingen, Germany, this behavior had only been observed in humans and other primates.
Researchers at the University of Tubingen in Germany found that some crows have subjective experiences and can perceive things consciously, something that, until then, had only been observed in humans and other primates.
“The results of our study opens up a new way of looking at the evolution of awareness and its neurobiological constraints,” said co-author Andreas Nieder, a professor at the University of Tubingen.
In the study published last week in the journal Science, the researchers explain that the ability to think consciously, for humans and non-human primates, is located in the cerebral cortex.
So, over the years, scientists have wondered whether species whose nervous system is structured differently, without the cerebral cortex, also had this ability.
To track conscious processes in birds, the researchers trained two carrion crows (Corvus corone) to report with their heads the presence or absence of a stimulus on a screen.
Most of the stimuli were perceptibly unmistakable, and the crows reliably signaled their presence or absence.
However, some stimuli were so weak that they were on the threshold of perception – and it was here that the subjective perception of crows came into play.
For the same weak stimulus, the animals sometimes indicated that they had seen it, while in other cases they did not react.
The activity of their nerve cells was recorded throughout the process.
The researchers found that when the crows reported seeing something, the nerve cells were active in the period between the presentation of the stimulus and the behavioral response.
In addition, it was possible to predict the subjective experience of crows in relation to the stimulus based on the activity of nerve cells.
“Nerve cells that represent visual input without subjective components are expected to respond in the same way to a visual stimulus of constant intensity,” Nieder explained.
“Our results however conclusively show that nerve cells at higher processing levels of the crow’s brain are influenced by subjective experience, or more precisely produce subjective experiences.”
This means that, in terms of evolutionary history, the origins of consciousness can be much older and more widespread in the animal kingdom than previously believed.
That’s because the last common ancestors between humans and crows lived 320 million years ago.
“It is possible that the consciousness of perception arose back then and has been passed down ever since,” Nieder suggested.
An alternative scenario suggests that consciousness developed independently in these distantly related species.
“In any case, the capability of conscious experience can be realized in differently structured brains and independently of the cerebral cortex,” Nieder concluded.