Data from: Odorant dominance in olfactory-compound processing: what makes a strong odorant?

The question of how animals process compound stimuli remains controversial as opposing views propose that compounds are processed analytically, as the sum of their elements, or holistically, as unique entities different from their elements. Overshadowing is a widespread phenomenon that can help deciding between these alternatives. In overshadowing, an individual trained with a binary compound learns one element better at the expense of the other. Although element salience (learning success) has been suggested as a main explanation for overshadowing, the mechanisms underlying this phenomenon remain unclear. We studied olfactory overshadowing in honey bees to uncover the mechanisms underlying olfactory-mixture processing. We provide the most comprehensive dataset on overshadowing to date based on 90 experimental groups involving more than 2700 bees trained either with 6 odorants or with their resulting 15 binary compounds. We found that bees process olfactory compounds analytically and that against prior views, salience alone cannot predict overshadowing. After normalizing learning success, we found that an unexpected feature, the generalization profile of an odorant, was more determinant for overshadowing. Odorants that induced less generalization enhanced their distinctiveness and became dominant in the compound. Our study thus uncovers the features that determine odorant dominance within olfactory compounds and allows referring this phenomenon to differences in neural activity both at the receptor level and in the antennal lobe, the primary olfactory neuropile of the insect brain. We suggest that this feature should be considered for further analyses of compound processing in animals.