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.
