What branch of psychology is this?

Question

In my English class my teacher mentioned a branch of psychology where you read annotations people make in a book, and you figure out what the person who made those annotations is like. What is this called?

Answer 1

Broadly, whenever you are trying to use data (here, annotations) from a single person to try to understand just that one person, you can consider that psychobiography, a case study in personality, or the idiographic methodology applied in personality psychology. The kind of activity your teacher describes is actually what got me into psychology, except I was interested in poems instead of annotations :)