And also primarily because of familiarization. We're familiar with the words so we can recognize them even when they're out of order. If it weren't for that we wouldn't know what the hell a scrambled word was even if the first and last letter remained the same.
For example, ettxogcaie. <--You can't read that without a problem huh? Because you're not familiar with the word.
Excogitate, meaning 1)To consider or think (something) out carefully and thoroughly 2) to study intently and carefully in order to grasp or comprehend fully. Etc.