"Flowers for Algernon" By Daniel Keys, published in Fantasy and Science Fiction.
Copyright 1959 by Mercury Press.

May 25

They've been feeding Algernon, who now refuses to work the shifting-lock problem. Everyone identifies me with Algernon. in a way we're both the first of our kind. They're all pretending that Algernon's behavior is not necessarily significant for me. But it's hard to hide the fact that some of the other animals who were used in this experiment are showing strange behavior.
Dr. Strauss and Dr. Nemur have asked me not to come to the lab any more. I know what they're thinking but I can't accept it. I am going ahead with my plans to carry their research forward. With all due respect to both of these fine scientists, l am well aware of their limitations. If there is an answer, I'll have to find it out for myself. Suddenly, time has become very important to me.