Habituation of the proboscis extension response induced by sugar tarsal stimulation was individually studied in males of Drosophila melanogaster all along the adult life span (2–71 days of age at 25°C). A polynomial regression fits the best the results: the speed of acquisition of this kind of learning decreases between the ages of 3 and 35 days, a plateau being observed in flies older than 35 days. Similar results have been previously obtained using associative learning tasks of increasing complexity. These effects of age could be due to a memory impairment, but also to deficits in the process of central inhibition of irrelevant motor responses.