Figure 8. PCA. To assess the important dimensions of category tuning, a PCA was performed across tuning profiles of FFA voxels. The tuning profiles were pooled across subjects before PCA. The first three PCs account for 55.8 ± 8.6% (mean ± SD across subjects) of the variance in category responses of FFA voxels (first PC, 32.1%; second PC, 12.0%; third PC, 11.9%). These PCs are presented in separate graphs, each formatted as in Figure 5. a, The first PC is broadly tuned for categories that appear in civilized contexts, such as humans, animals, vehicles, indoor spaces, roads, and devices (p < 0.05, Monte Carlo test, FDR corrected). b, The second PC distinguishes categories related to living things and their interactions, such as animals, humans, body parts, and communication verbs from nonliving categories, such as vehicles, indoor spaces, devices, and events (p < 0.05). c, The third PC distinguishes people from animals and nonliving categories, including vehicles and devices (p < 0.05).