He was lonely as a child and had problems caused by his Attention Deficit Disorder (ADD).
Nelson attended Swarthmore college where he earned a BA in philosophy. In 1960, he enrolled in graduate school at Harvard. During his first year he attempted a term project creating a writing system similar to a word processor, but that would allow different versions and documents to be linked together nonlinearly, by association. This was, in part, an attempt to keep track of his own sometimes frantic associations and daydreamings brought about by his ADD.