Other studies have shown that rhesus macaques and honeybees also demonstrate an understanding of zero. Multiple studies have shown that monkeys carry specially tuned neurons for the number zero, just like crows.
NICOLETTA LANESE: The concept of zero, as used in a number system, fully developed in human society around the fifth century A.D., or potentially a few centuries earlier… That idea may sound obvious, but following the conception of zero as a numerical value, the field of mathematics underwent a dramatic transformation. “If you ask mathematicians, most of them will probably tell you that the discovery of zero was a mind-blowing achievement,” said Andreas Nieder, a professor of animal physiology in the Institute of Neurobiology at University of Tübingen in Germany…
Zero represents that emptiness, and “that obviously requires very abstract thinking … thinking that is detached from empirical reality,” Nieder said. And now, by peering into the brains of crows, Nieder and his colleagues have discovered that the birds’ nerve cells, or neurons, encode “zero” as they do other numbers. The birds’ brain activity patterns also support the idea that zero falls before “1” on crows’ mental number line, so to speak.
In the new study, published June 2 in The Journal of Neuroscience, the team ran experiments with two male carrion crows (Corvus corone), during which the birds sat on a wooden perch and interacted with a computer monitor in front of them. In each trial, a grey screen containing zero to four black dots popped up in front of the crows; this “sample” image was followed by a “test” image containing either the same or a different number of dots…
The crows were trained to peck at the screen or move their heads if the two images matched one another, and to remain still if they did not match… This phenomenon is known as the “numerical distance effect,” which can also be observed in monkeys and humans during similar tests, Nieder told Live Science….
In a previous study using the same setup, the group showed that crows could successfully identify the matched and unmatched pairs of images about 75% of the time… This previous study did not include an empty screen, standing in for zero, but it did demonstrate that the crows could differentiate an image containing three dots from a screen containing five, for instance…
In the more recent study, which included a blank screen, “what we found is that the crows, after this training, could discriminate zero from the other countable numerosities,” Nieder said. However, importantly, the birds still demonstrated the numerical distance effect in trials that included the empty screen.
That means that the birds mixed up the zero-dot image with the one-dot image more often than with two-, three- or four-dot images, Nieder explained. “This is an indication that they treat the empty set, not just as ‘nothing’ versus ‘something,’ but really as a numerical quantity,” in that they perceive zero dots as proximal to one dot.
To better understand the brain activity behind these behaviors, the team implanted tiny, glass-coated wires into the birds’ brains to record electrical activity while the crows repeated the behavioral tests… The avian pallium belongs to a larger brain region called the telencephalon; humans also have a telencephalon, of which the cerebral cortex, the wrinkled outer layer of the human brain, is one part…
In the prior 2015 study, the team also gathered recordings from the pallium and specifically zoomed in on one key region, known as the nidopallium caudolaterale (NCL)… In the NCL, the team found that certain subgroups of neurons went wild when specific numbers of dots appeared on the screen. Some would begin rapidly firing in response to two dots, while others kicked off for four, for example…
In the new study, the team repeated this experiment with the addition of the zero-dot screen. In all, they took recordings from more than 500 neurons, 233 in one crow and 268 in the other. As before, they found that different subsets of NCL neurons lit up in response to different numbers of dots, but in addition, another subset fired in response to the blank screen. These neurons became less and less active the more dots popped up on-screen — or the further from zero the number grew.
In combination, the observed patterns of behavior and brain activity suggest that, yes, crows indeed grasp the concept of zero, the authors concluded. What utility this holds for the animals, if any, remains unclear, Nieder told Live Science. While being able to distinguish one piece of fruit from two can be useful for survival, for instance, “I don’t see an immediate advantage for these animals to understand nothing as a quantity,” he said.
Other behavioral studies have shown that rhesus macaques and honeybees also demonstrate an understanding of zero. In terms of brain activity linked to zero, multiple studies have shown that monkeys carry specially tuned neurons for the number zero, just like crows… Nieder said he’d be surprised if animals like amphibians or reptiles could do mathematical calculations that rely on an understanding of zero, since their learning capabilities don’t match that of mammals and birds.
But given that birds and mammals split off from their common ancestor well before the extinction of the dinosaurs, the fact that they share overlapping cognitive abilities is also remarkable, Nieder said… “That’s the fascinating aspect, that evolution obviously found different anatomical ways, independently, to equip those birds and mammals with high-level cognitive functions”. SOURCE…
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