Evening star., 1932-02-28

represent perhaps one o9 the G1rSt great steps
In experimental psychology A bell was rung
each time that food was given. After several
repetitions the bell was rung alone and found
to produce the same reaction, watering Of the
mouth.
THUS q new kind Of reflex had been set I'D
] which was not present In the dog before the
experiment. The BEN stimulus now acted as o
sort Of signal stimulus for the food
A new set Of nervous connections had been
set up in the dog by this experiment. by which
the message from the ear was automatically
routed to the salivary gland. A Conditioned"
reflex is the name that Pavlov gave this kind Of
reflex as contrasted with the "unconditioned"
reflex of food, saliva.
AL that Is necessary for the formation of
such conditioned ref1exes in the dog is that the
two stimuli be presented to the animal at the
same time when It is in a receptive mood.
Men or animals are subject to complex conn
binations of stimuli every hour Of the day. En-
thusiastic psychologists Of the behaviorist school
believe that practically all the powers Of the
human mind can be explained in this way.
Others not going so far, agree that the Pavlov
type of experiment is very powerful explanatory
mechanism for large regions Of human behavior.
If non-living matter can be made to show
behavior that Is formally indistinguishable
from the conditioned reflex, 1t is long step
toward establishing the idea that the brain In
just q particular kind Of machine.
This is Just what DIR. Hull of Yale University
and his co-workers have done They have
made machines that, for two specially chosen
stimuli, can show the conditioned reflex IN all
Of its essential aspects.
DR. HULL and his associates can be said to
- teach" their apparatus to light the bulb
by means Of one of the storage cells without the
fHalvN fI1cS
alone evoke the response" In another similar
model constructed by DR.. Baernstein, a COM
bination Of temperature regulators with mag
netic relay switches achieved the same result.
From the start Of the experiment. the closing
Of one switch On the HuH-Krueger machine.
which can be called the food" switch lights
the lamp. Lighting the lamp corresponds to
the secretion Of saliva IN the dog Other
switches In the circuit, called the bell"
switches. win not light the lamp at the start
To teach the machine that bell" number one
stands for food, the scientist depresSes the food
switch and bell number one switch several
times together
This is exactly the equivalent of presenting
the food and bell simultaneously to the dog. II
the scientist now presses the bell number one
switch alone, he finds that it now has the
power to light the lamp without the assist
ance Of the food switch The electrical dog
has learned his lesson!
The same process can be repeated with any
one Of the other bell" switches.
It is not claimed by the inventors that their
device actually shows how the brain works.
The Hull machine simply initiates brain action
and so helps convince those who have difficulty
in accepting the creed that man is a machine.
This philosophical idea Of mechanism" was
stated clearly long time ago by the physician
of Frederick the Great of Prussia, La Metric.
BY arguments that were remarkably good for
his time this philosopher tried to prove that
no supernatural soul" was necessary to explain
man.