Ants learn from experience and hold grudges against aggressive competitors, a new study has shown. Research by a team of evolutionary biologists from the University of Freiburg in Germany, led by Dr Volker Nehring and doctoral student Mélanie Bey, found that ants remembered negative experiences and behaved more aggressively towards ants they had previously experienced as aggressive. But ants from the test nest were less aggressive towards those from different nests from which they had only experienced passive behaviour, according to the study published in Current Biology.