Study shows fish can count – up to 3

Tropical angelfish can distinguish between larger and smaller quantities and can count up to three.

Washington: Math skills extend to fish, since new research has found that tropical angelfish can distinguish between larger and smaller quantities, with an additional ability to ‘count’ up to three.
Co-author Robert Gerlai, a University of Toronto Mississauga professor of psychology, and Luis Gomez-Laplaza of the University of Oviedo in Spain exploited the previously determined tendency of angelfish to seek protection in unfamiliar environments by joining the largest possible fish group, called a shoal.

To rule out possible confounding effects arising from sexual interactions, the researchers only used juvenile angelfish for their experiments.

Test fish placed in special compartmentalized tanks were given a simultaneous choice between shoals containing different numbers of fish.

The angelfish were always able to select the larger of two groups so long as the ratio between the shoals was 2:1 or above. Below that ratio, their choices were less predictable, suggesting a limit to their quantity estimation abilities.

After the findings were published, the researchers, according to Gerlai, "have already collected new data suggesting that angelfish can discriminate much more precisely than this. That is, angelfish can tell the difference between 3 and 2, for example."

"This ability does resemble ``counting`` individual items as opposed to estimating quantities, but this counting ability does not extend beyond three," Discovery News quoted him as saying.

Precise counting ability likely does not benefit fish much, so they have probably not evolved skills beyond those detected by the scientists.

Estimating group sizes, however, allows the fish to enjoy better protection in larger groups and improved food detection, with more eyes on the lookout for food sources. The ability to choose between larger and smaller quantities, therefore, has survival value for fish.

The findings appear in a new Animal Cognition paper.