Long-lasting generalization triggered by a single trial event in the invasive crayfish Procambarus clarkii.

Behavioural flexibility allows to adapt to environmental changes, a situation that invasive species have often to face when colonizing new territories. Such flexibility is ensued by a set of cognitive mechanisms among which generalization plays a key role, as it allows to transfer past solution to solve similar new problems. By means of a habituation paradigm, we studied generalization in the invasive crayfish Procambarus clarkii. Once crayfish habituated their alarming response to a specific water jet, we tested whether habituation transferred to a new type of water jet. Although habituation did not generalize when the new stimulus was initially presented, it surprisingly emerged 15 and 45 days later. Hence, remarkably, in P. clarkii a single presentation of a new event was sufficient to trigger a long-lasting form of learning generalization from previous similar stimuli, a cognitive ability that may concur in providing adaptive advantages to this invasive species.