the door
where the cat could see it. At first, the animal escaped from the cage by
freeing the door during its aimless scrambling about the catch, but as
trial after trial was made, the time necessary for the cat to make its way
out was shortened, until after seventy-five or one hundred trials, the
animal immediately opened the door and seized the food. In mechanical
terms, the connection between "scrambling about the door" and "freedom to
get the meat" became established by numerous repetitions until the
originally disconnected elements were physiologically associated and made
inseparable. When animals like horses and seals and dogs are trained for
the circus, it is by exactly the same method, for training consists merely
in the establishment of a psychological sequence so that the performance
of one series of acts leads mechanically to others. Thus we learn that the
psychological property called intelligence is the ability to establish
wide relations between numerous activities which are themselves of a more
or less complex nature; and we find also that because these elements are
ultimately nerve-cell and sense-cell reflexes, an intelligent response is
quite as machine-like as any and all of its elements. A difference in
degree of complexity and extent is the only thing that places intelligence
apart from instinct and reflex action, for the units are the same in all
cases,--so far as science knows.

The apes are of the greatest value in providing the transition from the
grade of intelligence to the human level where reason is found. Whether or
not a chimpanzee can reason at all is less important than the fact that
its total "mental" powers are lower than those of man, and higher than
those of inferior mammalia. Apes are far more susceptible to training than
cats and dogs, because their improved nervous mechanism enables them to
establish a psychological sequence with greater facility. If we are to
judge by the facts at hand, these creatures possess a low order of
mentality, like, but by no means equivalent to, that of man.

At the end of the comparative scale, we reach the human mind which is
characterized by its ability to perceive and recognize far wider relations
than those which are involved in intelligence. Human consciousness is the
stream of thoughts and feelings which constitute the immediate contents of
mind. In our own case, we know both the activities we perform and some of
the internal phenomena with whic