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Specialized But Flexible

Hawk moths are specialized to recognize the odors from specific plants but can learn to recognize and follow other plant odors. [Also see Report by Riffell et al.] Who can resist the bouquet of Christmas baking? It directly reminds us of positive experiences during early childhood. Odorants included in this mixture are also very likely to be innately attractive to humans, because they signal sugar and proteins. In contrast, most people can easily resist the flavor of surströmming, a Swedish national dish consisting of fermented herring that is—and smells like—rotten fish. Rotten fish emits compounds such as dimethyl sulfide, which is innately repellent to humans. The love of this food and the corresponding odors needs considerable learning. On page 200 of this issue, Riffell et al. (1) show that moths, which are usually specialized pollinators, can also learn to appreciate odors that are not their innate preference (see the figure). They also describe a potential neuronal substrate of this environmentally driven switch from specialized to flexible.