BEHAVIOR OF ANIMAL ORGANISMS 473 



individuality of the habit will then become apparent. Habits exhibited 

 with instincts make it seem as if the instincts were subject to modification. 

 However, the same test of comparison with other individuals may be 

 applied to separate the habitual from the instinctive element when the 

 two are combined. 



522. Learning. — The fact that habit involves repetition and in this 

 sense learning has led to its confusion with intelligence, but learning by 

 repetition without an appreciation of cause and effect is not at all the 

 same as the learning which accompanies intelligent activity. 



523. Intelligence. — Intelligence on the part of an animal is the 

 capacity to profit by previous experience. It is distinguishable from 

 habit by requiring few if any repetitions for its development and by 

 its free modifiability. Habits, though capable of modification, are 

 modified slowly and by repetition, in the same manner as that by which 

 they are formed. An intelligent animal, as opposed to one controlled 

 by habit, changes its behavior quickly, adjusting it to the results of past 

 experiences. 



Intelligence is usually considered as involving (1) associative memory, 

 (2) consciousness, and (3) ability to exhibit emotions and to feel pain and 

 pleasure. 



By associative memory is meant the ability to connect previous experi- 

 ences with the results of such experiences — in other words, to appreciate 

 cause and effect — and to profit by that ability. An insect acting only 

 from instinct will persistently try to reach a certain opening even though 

 beaten back time after time. An animal, like a dog, when guided by its 

 intelligence, will, if beaten back, retire and endeavor to find another 

 means of escape. Consciousness in the sense in which it is here used 

 implies this awareness of cause and effect. 



Emotions are somewhat difficult to define because different theories 

 are held as to their nature. They are produced under certain conditions 

 in the brain of intelligent animals, but they seem to be affected by condi- 

 tions in other parts of the body. Especially is the production of certain 

 emotions stimulated by the presence of particular hormones in the blood. 

 The physiological state of the body predisposes the organism to anger or 

 fear. Emotional conditions often have a controlling effect in the sus- 

 ceptibility of the body to pain, for an intelligent animal under great emo- 

 tional excitement is insensible to injuries which under normal conditions 

 would cause severe pain. This has often been noted in human experience. 

 Three of the most primitive emotions are anger, fear, and love. These 

 have their counterparts in instinctive activity, which frequently gives rise 

 to confusion. We speak of the "angry bee" when undoubtedly the bee 

 is actuated only by an instinct which leads it to defend itself or its home. 

 An insect frequently flies as if trying to escape under the influence of 

 fear, when it is only the instinct which is aroused by the sight of move- 



