This is Pavlov law of temporal contiguity in psychology. If there is a big time difference then dog will not learn to associate the two stimuli. He was awarded noble prize in psychology in 1904. read more
Pavlov won the Nobel Prize for Physiology or Medicine in 1904, becoming the first Russian Nobel laureate. A survey in the Review of General Psychology, published in 2002, ranked Pavlov as the 24th most cited psychologist of the 20th century. read more
Pavlov and his studies of classical conditioning have become famous since his early work between 1890-1930. Classical conditioning is "classical" in that it is the first systematic study of basic laws of learning / conditioning. read more