The primate-IT object representation is inherently categorical

Hierarchical clustering of IT response patterns in monkey and human. In order to assess whether IT response patterns form clusters corresponding to natural categories, we performed hierarchical cluster analysis for human (top) and monkey (bottom). This analysis proceeds from single-image clusters (bottom of each panel) and successively combines the two clusters closest to each other in terms of the average response-pattern dissimilarity, so as to form a hierarchy of clusters (tree structure in each panel). The vertical height of each horizontal link indicates the average response-pattern dissimilarity (the clustering criterion) between the stimuli of the two linked subclusters (dissimilarity: 1-r). The cluster trees for monkey and human are the result of completely independent experiments and analysis pipelines. This data-driven technique reveals natural-category clusters that are consistent between monkey and human. For easier comparison, we colored subcluster trees (faces: red, bodies: magenta, inanimate objects: light blue). Early visual cortex (Figs. 5, 6, S5) and low-level computational models (Figs. S6, S7) did not reveal such category clusters.

References

Matching categorical object representations in inferior temporal cortex of man and monkey ,
Kriegeskorte N, Mur M, Ruff D, Kiani R, Bodurka J, Esteky H, Tanaka K, Bandettini P. (2008). Neuron 60(6): 1126-41.