46 Animal Intelligence 
more quickly, Here, too, accident may play a part, for a 
cat may merely happen to be attending to its paw when it 
claws. The kind of acts which insure attention are those 
where the movement which works the mechanism is one 
which the cat makes definitely to get out. Thus A (O at 
front) is easier to learn than C (button), because the cat 
does A in trying to claw down the front of the box and so 
is attending to what it does; whereas it does C generally 
in a vague scramble along the front or while trying to claw 
outside with the other paw, and so does not attend to the 
little unimportant part of its act which turns the button 
‘round. Above all, Gimplicity and definiteness in the act 
make the association easy) G (thumb latch), J (double) 
and K and L (triples) are hard, because complex. \E is 
easy, because directly in the line of the instinctive im- 
pulse to try to pull oneself out of the box by clawing at 
anything outside. It is thus very closely attended to. 
The extreme of ease is reached when a single experience 
stamps the association in so completely that ever after the 
act is done at once. This is approached in I and E. 
In these experiments the sense-impressions offered no 
difficulty one more than the other. 
Vigor, abundance of movements, was observed to make 
differences between individuals in the same association. 
It works by shortening the first times, the times when the 
cat still does the act largely by accident. Nos. 3 and 4 
‘show this throughout. Attention, often correlated with lack 
of vigor, makes a cat form an association more quickly after 
he gets started. No. 13 shows this somewhat. The ab- 
sence of a fury of activity let him be more conscious of what 
he did do. 
The curves on pages 57 and 58, showing the history of 
cats 1, 5, 13 and 3, which were let out of the »ox Z when 
