I 4 JOSEPH U. Y ARE ROUGH 



of the current passed over these wires is so controlled that the 

 animal never becomes frightened by a severe shock. 



This box was developed from the one used by Carr and Free- 

 man 1 in their experiments. The following improvements were 

 made in the construction of the present box : i ) The glass cover 

 was extended so that the animal is not required to come out in the 

 open until it enters the food-box. 2) There is but one door to 

 the food-box. 3) The source of the stimuli is above the glass 

 cover, making contact with the animal impossible. Further- 

 more, it was necessary to increase the box in length and number 

 of compartments to secure sufficient time between the point 

 of choice and the food-box for the presentation of the two 

 stimuli with an interval of six seconds between them. The 

 animals seldom made the distance in so short a time, but in their 

 most rapid responses the entire distance was traversed. The 

 additional apparatus used in presenting the pair of stimuli in 

 certain temporal relations are rather tediously described below. 



About 1 8" above the center of the box a light of very low 

 candle power is suspended. The light from this source is just 

 sufficient to enable the experimenter to see the animal move 

 through the maze. Similarly, an electric buzzer is suspended 

 10" above the glass cover of the middle portion of the box and 

 connected with the batteries and the timing apparatus as is in- 

 dicated in Fig. 2. The timing apparatus is, in turn, attached to 

 a Zimmerman kymograph by screws E and E 1 in a way shown 

 very well in Fig. 3.. The revolving disc upon which the arm A 

 rests is in direct connection with the shaft of the kymograph, 

 which turns it around the dial at any speed desired. The dial is 

 graduated so as to read seconds, half seconds, and quarter sec- 

 onds, when the kymograph is adjusted at the rate of one revolu- 

 tion for every 15 seconds. Each of the numerals, therefore, 

 represents the number of seconds necessary for the arm A to 

 move from the zero point to the respective numeral as it appears 

 on the dial. The contact B may be moved along the dial and 

 firmly set at any point by the thumb screw. The arm A is not 



iCarr, H. A., and Freeman, A. S., "Time Relationships of Association," 

 Psychol Rev., Vol. XXVI, p. 465. 



