Myrmica sabuleti Workers Cannot Acquire Serial Recognition if not Rewarded

Having previously found that workers of the ant Myrmica sabuleti can acquire serial recognition when rewarded after having walked a correct visual sequence, we here examined if they can acquire this type of learning (that is recognizing a correct sequence presented together with wrong ones) without being rewarded. Using the same colonies two months later and sequences made of four never previously presented elements, we observed that these ants could not significantly acquire serial recognition. Thereafter, rewarding the ants at each step (element) of the sequence, they could progressively acquire some serial recognition, reaching a score of 60% after seven training days. This score no longer increased the day after, being thus the maximum score the ants could reach. The ant M. sabuleti can thus acquire serial recognition only if duly rewarded during training. Moreover, on the basis of their responses to three wrong sequences during testing, it might be presumed that, when being rewarded at each element of the sequence and not at the end of it, the ants better memorize the first element of the sequence. These studies have demonstrated that ants, particularly the workers of M. sabuleti, can acquire serial recognition only through operant conditioning.