Fish can perform basic arithmetic
Studies have shown that all classes of vertebrates—and even some invertebrate species—have the cognitive ability to discriminate among different quantities. For example, many kinds of studied animals can distinguish specific numbers of objects in their environment. This mathematical skill is theorized to be important in wide-ranging animal behaviors such as herding, schooling, and flocking; choosing among mates based upon visual characteristics, such as number or size of stripes; and estimating amounts of food sources during foraging. Fewer kinds of animals, however, have been shown to possess the cognitive ability to perform addition and subtraction, which are more complex numerical tasks. To date, researchers have documented this arithmetical ability in primates and birds, as well as in spiders and honeybees. Now a new study has discovered that fish—specifically cichlids and stingrays—can also perform addition and subtraction of a quantity of one in the number space from one to five. The findings are unexpected because neither species is known to have an obvious ecological or behavioral need for this mathematical ability. Furthermore, the findings emphasize that a neocortex—the part of the brain that evolved in mammals and had long been considered necessary for certain higher-level cognitive abilities—is not required for performing basic arithmetical operations. See also: Arithmetic; Batoidea; Brain; Cognition; Evolution; Fish; Mammalia; Mathematics
