Number sense, the ability to recognize quantitative changes in a small collection of objects, is a capability granted to some animal species. Many birds, for example, have a good number sense. If a nest contains four eggs, one can safely be taken, but when two are removed the bird generally notices and deserts the nest. Thus, birds can distinguish two from three and are said to have a number sense that is around three.
An interesting experiment was conducted by a squire who wanted to shoot a crow which nested in the watchtower of his estate. The squire tried to sneak up on the crow, but each time the crow would leave, watch from a safe distance, and not come back until the man left the tower. One day, the squire decided to bring another man with him to the tower. After some time of hiding, one of the men left the tower and the other stayed, expecting the crow to come back. However, the crow was not fooled, and stayed away until the other man exited the tower. The next day, the same experiment was repeated, but this time three men entered the tower and two left. Still, the crow was not fooled. The following day, four men entered, and three men left. Again, the crow waited for the fourth man to exit before returning to its nest. On the next day, five men went into the tower, and four men left. This time, the crow fell for it and returned to the tower, not realizing that only four of the five men had exited the tower.
A similar experiment was conducted with a goldfish, where different piles of seed were given to it and its reaction was observed. The fish showed evidence of being able to distinguish three from one, four from two, three from two, four from three, and six from three, while almost always confusing five and four, seven and five, eight and six, and ten and six.
This evidence may lead one to believe that people would have a very good number sense. Unfortunately, it turns out that people do not. In fact, experiments have shown that an average person has a number sense that is only around four. Many tribes that have not yet developed finger counting have a hard time discerning the quantity four. They generally use the quantities one, two, three, and many, which would include everything from four and on. Also, small children are almost always able to notice when something is missing from a relatively small group of three or four objects, but are usually unable to distinguish quantitative differences when the unit count exceeds four.
Indeed, the human kind ranks quite low compared to the rest of the animal kingdom, but one of the most important abilities that put us so far ahead of all other animals is our ability to count. Counting, which usually begins on our fingers, is usually taught by another person or, though very seldom, by circumstance. This ability allows us to more than make up for our low number sense. After all, few of us would be able to look at two groups of 7 and 8 objects respectively and be able to tell the difference without making some basic calculations in the process. Though it may seem very natural, and can be done extremely fast, our ability to count should not be taken lightly for it has played a crucial role in the advancement of the human race.