192 Bulletin Wisconsin Natural History Society [Vol. 13, No. 4 
turned on a turtle on the plate would complete the circuit and 
would receive a shock when he touched the forceps at the end of 
the feeding stick. The current came from an induction coil con- 
nected with a dry cell. The coil made a faint buzzing sound and 
vibrated slightly. It therefore was removed from the table on 
which the box containing the turtles was placed, to a small stool 
which did not touch the table so that the turtles would be unable 
to feel this vibration and so associate it in any way with their 
feeding. 
The problem set for the turtles was to distinguish between a 
whistle and a bell. Both these instruments were sounded be- 
neath the table in such a way that there was no direct mechanical 
stimulation connected with their use. When the whistle was 
sounded the electric circuit was on, and any turtle attempting to 
feed received a shock. When the bell was ringing food was of- 
fered without danger of receiving the electric current. At first 
the trials were made alternately, but afterwards two, or three bell 
trials might be followed by one or more whistle trials or vice- 
versa in order that the animal might not react to mere rhythm 
of sounds. In each trial, care was taken not to give by move- 
ments of the hand, or in any other manner, any cue to the proper 
response. The severity of the shock used was varied considerably 
for different individual turtles. For the large turtle, No. Ill, a 
very slight shock was effective, while for the smallest turtle, No. 
I, a shock of much greater intensity was necessary. 
All the turtles learned their lesson. Their attempts to take 
food when the whistle was blowing became fewer and fewer, and 
increased in number when the bell rang, as the appended tables 
show. All were voracious feeders and extremely eager for their 
daily ration. They were very active and when tamed would 
swim quickly to the place of feeding whenever anyone approached. 
Often two or three would be sitting on the zinc plate in readiness 
to be fed before I had put my apparatus together. Several times 
I would start the trials with the whistle, and all would scramble 
off, to come back again when I rang the bell. Turtle No. I, how- 
ever, was often so eager for food that he would not listen to the 
bell and therefore would get a shock to remind him to be more 
careful next time. 
When a turtle grabbed the meat, he turned around and scrambled 
