40 Animal Intelligence 
hours is specified by 1 hr., 2 hrs., etc. In many cases the 
animal failed in some trial to perform the act in ten or 
fifteen minutes and was then taken out by me. Such fail- 
ures are denoted by a break in the curve either at its start 
or along its course. In some cases there are short curves 
after the main ones. These, as shown by the figures be- 
neath, represent the animal’s mastery of the association 
after a very long interval of time, and may be called memory- 
curves. A discussion of them will come in the last part of 
the chapter. 
The time-curve is obviously a fair representation of the 
progress of the formation of_the association, ofthe two 
essential factors in in the latter are the diseppearante of of all 
activity save the particular sort which brings su siitcess with 
it, and perfection of that particular sort.of-act.so that itis 
done precisely and at will) Of these the second is, on deeper 
analysis, found to be a p4rt of the first; any clawing at a 
loop except the particular claw which depresses it is theoreti- 
cally a useless activity. If we stick tothe looser phraseology, . 
however, no harm will be done. The combination of these 
two factors is inversely proportional to the time taken, 
provided the animal surely wants to get out at once. This 
was rendered almost certain by the degree of hunger. 
Theoretically a perfect association is formed when both 
‘factors are perfect, — when the animal, for example, does 
‘nothing but claw at the loop, and claws at it in the most 
(useful way for the purpose. In some cases (e.g. 2 in K on 
page 53) neither factor ever gets perfected in a great many 
trials. In some cases the first factor does but the second 
~does not, and the cat goes at the thing not always in the 
desirable way. In all cases there is a fraction of the time 
which represents getting oneself together after being 
dropped in the box, and realizing where one is. But for 
