Dr. Howard Gardner of Harvard University proposed that there are several types of intelligence: naturalist, logical, mathematical, musical, interpersonal, spatial or linguistic (many theories include eight or even nine types). The type of intelligence differs in everyone and is largely a natural phenomenon. Naturalists can easily find the difference between natural things like clouds, animals, plants, etc. Whereas mathematically intelligent people are quick at calculations, propositions and hypotheses. Musically intelligent persons are able to discern rhythm, tone or pitch and can identify sounds which a normal human being might easily miss. Those with spatial intelligence have a unique quality of thinking in pictures. On the other hand linguistically intelligent ones use words for imaginative activities.