Animals Count and Use Zero. How Far Does Their Number Sense Go?

Understanding numbers is often seen as a distinctive human faculty. It is a mark of intelligence that sets us apart from other animals.
However, this could not be further from reality. When navigating to nectar sources, honeybees use landmarks as a guide. Before deciding whether they will attack or retreat, lionesses count the number of roars that an intruding pride makes. Some spiders keep track how many prey they catch in their web, while ants keep track their steps. One species of frog bases their entire mating ritual on the number of prey caught in its web. If a male calls out a short pulsing note called "chuck", his rival will respond by adding two chucks to his call. The first frog responds with three, then the second with four and so on until they run out.

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Scientists have found that almost every animal studied (insects, cephalopods and amphibians, birds, and reptiles) can distinguish between different objects or sounds within a sequence. They have an approximate sense for quantity, not just a sense that something is greater or less than. For example, two objects are distinct from three and 15, while 20 is distinct from twenty. According to Giorgio Vallortigara (a neuroscientist from the University of Trento, Italy), this mental representation of set size is called numerosity.

Researchers are now discovering more complicated numerical abilities in animal subjects. Many species are capable of abstracting, and some even have the ability to perform simple arithmetic. However, a few species also have the ability to grasp zerothe quantitative concept. This is a paradoxical idea that can sometimes be difficult for very young children. Experiments have shown that honeybees and monkeys can treat zero as a numerosity. They place it on the same mental number line as numerosity one or 2. Researchers also reported in a June paper in the Journal of Neuroscience that crows could do this.

Content Male tngaras frogs add one sound to their calls when they compete in mating. Michale J. Ryan

These three species come from different taxonomic groups, including birds, insects, andprimates. This suggests that certain numerical abilities have been re-evolved throughout the animal kingdom. Scientists are still puzzled over how nature gifted animals with basic numbers skills, and what that could reveal about the origins of mathematics in humans. While there are many questions, neuroscientists have been able to expand their understanding of animal cognition. Brian Butterworth, a Cognitive Neuroscientist at University College London, and the author of Can Fish Count?, stated that even tiny brains such as those of bees and ants have a mechanism that allows them to understand the language of other universes.

A Competence for Number

Clever Hans, a Berlin-based horse, was famous almost 120 years ago. Clever Hans was able to do arithmetic with his hoof, tapping out the answers to multiplication, subtraction and division problems. A psychology graduate student quickly realized that the animal was simply paying close attention to subtle behavioral cues given by his trainer or others who had the answers.

This incident engendered a suspicion about the numerical abilities of animals that continues to this day. For example, some researchers suggest that, while humans may have a deep understanding of numerical concepts and animals can only distinguish between objects based on their quantity, when animals rely on more abstract characteristics like size or colour, they are not able to discriminate among them.