Hermann Ebbinghaus (1850—1909) examined learning by studying rote memory and forgetting. With himself as his own experimental subject, he used meaningless syllables to form lists that he read several times until he could restate them with high accuracy. He also attempted to recall the same lists with delays of a few days or months and then recorded his discoveries as learning curves and forgetting curves. Edward Thorndike Edward Thorndike (1874–1949) presented his theory of the "Law of Effect" in 1898. According to this theory, humans and other animals learn behaviors through trial-and-error methods. Once a functioning solution is found, these behaviors are likely to be repeated during the same or similar task. It was his work on learning theory that resulted in operant conditioning within behaviorism. His theory of operant conditioning is learning from the consequences of our actions and behavior. Ivan Pavlov Ivan Petrovich Pavlov (1849–1936), a Russian physiologist, contributed to research on learning. Knowing that a hungry dog salivates when food is present, he trained dogs to salivate to an arbitrary external stimuli. This was done by pairing a natural stimulus (such as food) with a novel stimulus (e.g., a metronome) to provoke the desired response in dogs. That proved his thesis that he could make a dog salivate by just the presentation of the sound of a bell. Pavlov's behavioristic approach to learning became known as classical conditioning.[9] John Broadus Watson John Broadus Watson (1878–1958) also used this method of learning (e.g., he caused a young child, not previously afraid of furry animals, to become frightened of them) and argued that it was sufficient for the science of psychology, specifically behaviorism. Watson is often referred to as being the founder of the school of behaviorism. From 1920 to 1960, this school influenced a great deal of North American psychology. Burrhus F. Skinner Burrhus F. Skinner (1904-1990) developed operant conditioning, in which specific behaviors resulted from stimuli, which caused them to appear more or less frequently. By the 1920s, John B. Watson's ideas had become popular and influential in the world of psychology and classical conditioning was being explored by other behaviorists. Skinner's was one of these behaviorists. He thought that in order to understand behavior we needed to look at the causes of an action and its consequences. He called this operant conditioning. Skinner is referred to as the father of operant conditioning but his theory stems