METHODS OF EXHIBITING REACTIVE TENDENCIES 



23 



Ex 



En 



Figure 5.— Diagram of lever-key mechanism for raising and lowering doors. En, 

 entrance door; Ex, exit door; T, observer's table: s, hinged lever key in vertical 

 position; p, same, in horizontal position; A, pulley for cord between entrance 

 door and lever key; B. pulley for cord between exit door and lever key; C, 

 second pulley for cord from exit door. 



For the medium sized apparatus also, the lever key mechan- 

 ism is feasible, but it requires considerably more space and 

 much greater effort on the part of the experimenter. A sub- 

 stitute for it is the weighted cord mechanism. 5 A cord with 

 appropriate carrying pulleys is provided for each door, and to 

 the end of the cord, which drops in front of the experimenter's 

 table and within easy reach, is attached an iron or lead weight 

 which is just sufficient to hold the door in position after it has 

 been raised by the experimenter. If the weight is too heavy, 

 the door will tend to rise at inappropriate times; if too light, it 

 will not stay in position after being raised. This device has the 

 defect of varying in reliability with humidity and temperature, 

 since the door will slide more or less easily in accordance with 

 these varying conditions. The lever mechanism is preferable, 



5 Described in previous papers on the multiple- choice method. A study of the 

 behavior of the pig Sus Scrofa by the multiple-choice method, Journal of Animal 

 Behavior, 1915, 5, p. 188. The mental life of monkeys and apes: a study of idea- 

 tional behavior, Behavior Monographs, 1916, 3, p. 14. 



