Homing pigeons use familiar smells to navigate their way across hundreds of kilometers of unfamiliar territory. Researchers have now confirmed that artificial odors cannot be used to stimulate or trigger a pigeon’s navigation system. This means that the so-called olfactory activation hypothesis—which has been proposed by some researchers—should be disregarded, argues Anna Gagliardo of the University of Pisa in Italy. Gagliardo and her colleagues have published their research in Springer’s Journal of Comparative Physiology A.