In spite of Charlie's research and hope for a cure for Algernon's regression, Charlie realizes that there is none. In "Flowers for Algernon," by Daniel Keyes, Charlie's intelligence reaches a level that exponentially surpasses his doctors, so when Algernon, the mouse, begins to show signs of deterioration, Charlie is determined to find an answer. His answer, unfortunately, is that,
"Artificially increased intelligence deteriorates at a rate directly proportional to the quantity of the increase." (Keyes 33)
This tells Charlie that his own deterioration will happen very quickly. Even though he knows this, Charlie is happy that he has been able to add knowledge about the brain to that of his predecessors.
The first symptoms Charlie begins to notice in himself are "signs of instability and forgetfulness." Soon after that, he becomes absent minded as well.