TASK DEFINITION: Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.
PROBLEM: troy smith (born july 20, 1984 in cleveland, ohio) is an american football quarterback that most recently played for the omaha nighthawks of the united football league.

SOLUTION: troy smith

PROBLEM: the vektor r4 is a south african assault rifle.

SOLUTION: vektor r4

PROBLEM: roger wolcott sperry (august 20, 1913 april 17, 1994) was an american neurobiologist and nobel prize winner.

SOLUTION:
roger wolcott sperry