In “On Deep History and the Brain,” Daniel Lord Smail suggests that human history can be understood as a long, unbroken sequence of self-modifications of our mental states.

We want to alter our own moods and feelings, and the rise of man from hunter-gatherer and farmer to office worker and video-game adept is the story of the ever proliferating devices — from coffee and tobacco to religious rites and romance novels –we’ve acquired to do so.