Conversation so far:
where was Sigmund Freud born?
the Moravian town of Freiberg.
when was he born?
CANNOTANSWER.
where did he go to school?
the University of Vienna.
what did he study?
philosophy under Franz Brentano, physiology under Ernst Brucke, and zoology under Darwinist professor Carl Claus.
when did he graduate?
1881.
Did he study anywhere else?
1876, Freud spent four weeks at Claus's zoological research station in Trieste.
did he do research anywehre else?
CANNOTANSWER.

Question: What did he do research on?
Self-contained rewrite: What did Sigmund Freud do research on?