Ants' Notion of Zero through the Perception of the Absence of an Odor

Workers of the ant Myrmica sabuleti can acquire the notion of ‘nothing’, i.e. a basic concept of zero, through olfactory conditioning, the best when the odor is unpleasant (onion odor) and when the response to the absence of the odor is rewarded. With a pleasant odor (lavender, rosemary or vanilla odor), the ants learn best when the response to the odor is rewarded. To our knowledge this is the first time that olfactory operant conditioning is obtained in animals by rewarding their response to ‘nothing’. The present work also points out: - the impact of the kind and quality of the cue to be learned on the animals’ learning score, - the improvement of a given learning over successive similar learning experiments, - the obtaining of a better learning when the reward is associated with the animals’ preference.