Rats can distinguish (and generalize) among two white wine varieties.

In the olfactory literature there is considerable debate about how differences in olfactory receptors across different species map onto variations in perceptual acuity and performance. Although humans have fewer functional olfactory receptors than most other mammals, it has been suggested that linguistic and cognitive abilities help compensate for this apparent deficit and enhance discriminative abilities, particularly through humans' ability to categorize sensory stimuli into conceptual categories. However, previous research suggests that non-human animals can learn complex categories, involving multiple perceptual dimensions, indicating that they can discriminate complex odor stimuli without language. We investigated generalization over complex olfactory categories by examining rats' discrimination of wine varieties, a challenging task for humans that has been suggested to rely heavily on human-specific linguistic, cognitive and categorization abilities. Nine rats were trained in an olfactory discrimination task (go/no-go) using a specific wine variety (Riesling or Sauvignon Blanc from different winemakers) as the S + . Rats were then tested using novel wines of the same varieties in unrewarded probe trials to assess their abilities to correctly assign instances of wine to specific categories. Interestingly, all nine rats successfully learned to discriminate the two varieties, and most rats generalized within two test trials to novel wines of the same varieties. We explore the implications of our results for olfactory concept formation and categorization more generally.