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Although knowledge indexes our experiences of the world, the neural basis of this relationship remains to be determined. Previous neuroimaging research, especially involving knowledge biased to visual and functional information, suggests that semantic representations depend on modality-specific brain mechanisms. However, it is unclear whether sensory cortical regions, in general, support retrieval of perceptual knowledge. Using neuroimaging methods, we show that semantic decisions that index tactile, gustatory, auditory, and visual knowledge specifically activate brain regions associated with encoding these sensory experiences. Retrieval of tactile knowledge was specifically associated with increased activation in somatosensory, motor, and premotor cortical regions. In contrast, decisions involving flavor knowledge increased activation in an orbitofrontal region previously implicated in processing semantic comparisons among edible items. Perceptual knowledge retrieval that references visual and auditory experiences was associated with increased activity in distinct temporal brain regions involved in the respective sensory processing. These results indicate that retrieval of perceptual knowledge relies on brain regions used to mediate sensory experiences with the referenced objects.

Young children tend to claim that moving artifacts and nonliving natural kinds are alive, but neglect to ascribe life to plants. This research tested whether adults exhibit similar confusions when verifying life status in a speeded classification task. Experiment 1 showed that undergraduates encounter greater difficulty (reduced accuracy and increased response times) in determining life status for plants, relative to animals, and for natural and moving nonliving things, relative to artifacts and non-moving things. Experiment 2 replicated these effects in university biology professors. The professors showed a significantly reduced effect size for living things, as compared with the students, but still showed greater difficulty for plants than animals, even as no differences from the students were apparent in their responses to nonliving things. These results suggest that mature biological knowledge relies on a developmental foundation that is not radically overwritten or erased with the profound conceptual changes that accompany mastery of the domain.

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