The ancestral Kaleds were indistinguishable from humans, yet the possibility of mutation into the creatures occupying Dalek casings was apparently integral to their DNA. It is therefore not entirely surprising that humans on occasion displayed the potential to mutate into creatures indistinguishable from mutant Kaleds. The species converted into Daleks, where left as simple nervous system tissue and mutilated flesh, where conditioned with Dalek programming, which they could seldom overcome, usually through intense emotion. They experienced mental illness due to the trauma of the conversion or their state of being as a Dalek, which only made them more dangerous. This could cause true insanity, which was only controlled by Dalek programming.