Remarkably, we found a significant linear relationship between the DegFact values distribution and the explicit human categorization. Most HC classes corresponded to an unambiguous DegFact distribution ( Figure 3B ), while HClevels 2 and 3 form a single class: HC-level 1, mean DegFact of 3.3, SD of 2.8 (IC 2.8-3.7); HC-level 2 and 3, mean Deg-Fact of 8.8, SD of 6.8 (IC 7.5-10.2); HC-level 4, mean DegFact of 15.9, SD of 7.8 (IC 12.7-19.1); HC-level 5, mean DegFact of 26.0, SD of 7.5 (IC 21.9-30.1). It is worth mentioning that the normalized heights of 18S and 28S peaks, and the interval between them after rescaling gradually decrease and then reverse with increasing degradation ( Figure 3B ).