Abstract

Young Myrmica sabuleti worker ants aged at most a few weeks and settled in small single-cohort colonies, were learned, by operant conditioning, to recognize either 2 or 3 dots displayed on a stand. When tested in front of two stands bearing different numbers of dots, one even and the other odd, their response was always higher towards the stand bearing the same parity as the one learned. They thus reacted to the parity corresponding to the number of dots they have learned to associate with the reward. These young ants were sensitive to the parity of a number of dots ranging from 1 to at least 6, but could not discriminate their parity when in front of 5 and 6. They were somewhat more responsive towards an even number than towards an odd number, having learned a number with this parity. A preceding study showed that older workers (experienced foragers) are sensitive to the parity of numbers of dots ranging from 1 to at least 7, and this equally whether the numbers are odd or even. Their limit of parity discrimination of close numbers is in front of 6 and 7. It therefore appears that, although present early on, the sensitivity of young workers to parity of numbers of elements and to number discrimination has to improve over the course of their lives, perhaps through an age-related maturation process, or through acquired experience.

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