Olfactory navigation versus olfactory activation: a controversy revisited.

In the early 1970s, Floriano Papi and colleagues proposed the olfactory-navigation hypothesis, which explains the homing ability of pigeons by the existence of an odor-based map acquired through learning. This notion, although supported by some observations, has also generated considerable controversy since its inception. As an alternative, Paulo Jorge and colleagues formulated in 2009 the olfactory-activation hypothesis, which states that atmospheric odorants do not provide navigational information but, instead, activate a non-olfactory path integration system. However, this hypothesis is challenged by an investigation authored by Anna Gagliardo and colleagues and published in the current issue of the Journal of Comparative Physiology A. In this editorial, the significance of the findings of this study is assessed in the broader context of the role of olfaction in avian navigation and homing, and experiments are suggested that might help to finally resolve the olfactory-navigation versus olfactory-activation controversy.