That the individual differences in the ability to memorize are very great, has always been observed. Modern psychology, however, has added to this knowledge an insight into the various kinds of differences and their proper causes. Let us notice the perception and imagery types. There are people who perceive and imagine very readily visual sensation groups. They give attention to the shape and color of the things rather than to any other sensible qualities, and they imagine visual shape or color very vividly so that the right and left, the above and below, of their imagery is clearly in their minds. In others auditory perception and auditory imagery are very vivid; in a third class of persons the same is to be said of kinesthetic mental states. We therefore distinguish visual, auditory, and kinesthetic types of consciousness. There may be also gustatory, olfactory, and other types, but they are of little practical importance. Extreme cases, where one of these classes of mental states is extraordinarily developed at the expense of all others, are rare. Eminent ability in art or music probably depends on such development. Generally, one kind of imagery is but slightly superior to the rest. There seem to be further individual differences with respect to a predominance of either word images or images of the things of nature. All these differences bring about numerous variations of memory. The visual type is able to play chess blindfolded, to repeat a memorized series of numbers somewhat slowly also backwards. To the auditory type these performances seem miraculous. But the former in recalling easily confuses similar looking elements of such a memorized series, which the latter would certainly distinguish because of their difference in sound. The auditory type, however, confuses elements that are similar in sound or accent. The auditory and kinesthetic types depend largely on reading aloud for memorizing, while the visual type is scarcely aided by it. These differences are of much importance for all the various kinds of professional activity. QUESTIONS 95. In what respect is memory the opposite of attention? 96. In what respect is reproduction by similarity superior to reproduction by simultaneity of previous experience? 97. Can you illustrate the relations between feeling and memory? 98. What is meant by the set of the mind? 99. Illustrate the dependence of memory on recency. 100. Illustrate the two laws of repetition. 101. What method has been devised for the diagnosis of memory which is not voluntarily revealed? 102. What is meant by perception or imagery types? 103. Can you illustrate the practical importance of the types of consciousness? § 10. PRACTICE