Counted Out

Recognizing the numerousness of a group is an important skill. Of course, we can spend time counting the individuals in a group if we want to be certain of the accuracy, but this is time consuming and laborious, not to say soporific as we claim counting sheep can be.

With up to about four, we don’t have to count. When there is a large group it's much more difficult to tell the exact number, but we can readily tell which group is the larger if we are confronted with two groups containing markedly different numbers. The bigger the difference, the more certain we are.

What this means is that we work with two numerical systems automatically and on an everyday basis, even if we claim to be horrified at anything mathematical. Some other species have been shown to have some numerical ability also.

In this week’s Public Library of Science, Agrillo et al pose the big question “Are their undergraduates more or less capable of counting than guppies?”(1). Female guppies were chosen because they are gregarious and go around in groups rather like some of our undergraduates.

Note that neither the undergraduates nor the guppies were required to attend any dry mathematical lectures during this study. Guppies especially don’t like things dry.

The mainly female group of undergraduates was asked to look at pairs of groups of dots and say which image had the most dots. Some had large numbers in and some had small (up to 4) in them. Their accuracy was plotted against the ratio of the numbers of the pairs.

Nobody was found that could speak Guppy, so experienced and very young guppies were given the choice of joining one of two shoals of different numbers of fish. Like the pictures of dots, large and small shoals were offered. As guppies are very fond of guppies, they were expected to join the bigger of the two shoals. Their accuracy was also plotted against shoal number ratio.

The result? Not quite a dead heat. The undergraduates had slightly better results than the fish, but the trends were much the same. For small numbers, the accuracy was number ratio independent. With big numbers, the accuracy fell as the groups approach similar sizes.

The conclusion drawn was that in estimating numbers, undergraduates operate in a very similar manner to guppies.

Not that this is a bad thing, it just means that the roots of our mathematical ability go back a very long way in evolution as numerousness is an important life-skill.


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