28 Animal Intelligence 
unless I was sure that his motive was of the standard 
strength. With chicks this is not practicable, on account of 
their delicacy. But with them dislike of loneliness acts as 
a uniform motive to get back to the other chicks. Cats (or 
rather kittens), dogs and chicks were the subjects of the 
experiments. All were apparently in excellent health, save 
an occasional chick. 
By this method of experimentation the animals are put 
in situations which call into activity their mental functions 
and permit them to be carefully observed. One may, by 
following it, observe personally more intelligent acts than 
are included in any anecdotal collection. And this actual 
vision of animals in the act of using their minds is far more 
fruitful than any amount of history of what animals have 
done without the history of how they did it. But besides 
affording this opportunity for purposeful and systematic 
observation, our method is valuable because it frees the 
animal from any influence of the observer. The animal’s 
behavior is quite independent of any factors save its own 
hunger, the mechanism of the box it is in, the food outside, 
(and such general matters as fatigue, indisposition, etc. 
Therefore the work done by one investigator may be re- 
peated and verified or modified by another. No personal 
factor is present save in the observation and interpretation. 
Again, our method gives some very important results 
which are quite uninfluenced by amy personal factor in any 
way. The curves showing the progress of the formation of 
associations, which are obtained from the records of the 
times taken by the animal in successive trials, are facts which 
may be obtained by any observer who can tell time. They 
are absolute, and whatever can be deduced from them is 
‘sure. So also the question of whether an animal does or 
does not form a certain association requires for an answer 
