68 IOWA ACADEMY OF SCIENCE Vol. XXV. 1918 



respect. The instructions are : If the sound is strong do not 

 respond, if it is weak, respond. This type of action requires a 

 high form of mentality, the power of deliberation and choice. 

 The observer has first to delay reaction and discriminate between 

 a weak and a strong sound, and after this is done, choose either 

 to act or not to act. 



5. A complex response to a complex stimulus — serial acti&n. 

 The highest form of action may be represented in a generic way 

 by presenting one from a group of stimuli calling for a partic- 

 ular one of a group of po.isible actions. For example, suppose 

 four bells are located in dififerent parts of the room and the 

 observer is seated at a tj^pewriter with two fingers of each hand 

 on designated keys with the instruction that each bell shall be 

 identified by a particular key so that, when that bell rings, the 

 correct key is to be pressed. "We then have a contrivance by 

 which the pressing of the key rings another bell which calls for 

 a similar action, and this keeps on indefinitely, making it pos- 

 sible to record the speed of action, the amount of action in a 

 given time, and the degree of reliability in terms of errors. 



6. Precision of action. The control of movement may be 

 measured in terms of precision in direction, precision in distance, 

 precision in force, and precision in time of movement. In 

 measuring precision of direction we use a drill gauge so mounted 

 with an electric pointer that the observer can put the pointer 

 into the hole without touching the margin of the hole ; if it 

 touches the bell rings. The test consists in finding for a given 

 form of movement how small a hole he can put the pointer into 

 without toi*ehing the edge, using a steady regular movement. 

 Similar tests may be made for distance, time, and force of action. 



7. Strength and endurance. — The ergograph. Here we 

 employ a new model of ergogi'aph in which a person is required 

 to m^sc his maximum lift against the spring with the biceps 

 and associated muscles in a given position, thirty consecutive 

 times, and a graphic record is made showing the exact amount 

 of each pull. The regularity and the rate in the falling off of 

 the strength of the pull in thirty trials is a fair index to relia- 

 bility and endurance. 



In order to make these tests available on a large scale, we 

 have encountered the very difficult problem of adapting instru- 

 ments. The instruments which we employ in the Psychological 

 Laboratorv for these tests would cost over a thousand dollars 



