How did Ebbinghaus contribute to psychology?

He made contributions in memory studies. Found that memory is better cor the first few and last few items in a string of nonsense syllables. He also discovered that most forgetting (more than 60 percent) occurs during the first nine hours after learning. After nine hours, the course of forgetting levels off.

(Psychology:a discovery experience by Stephen L. Franzoi; Pages 394, 376)