1 6 E. L. THORNDIKE. 



days, etc. If the interval was shorter the number of hours is 

 specified by i 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 failures 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 beneath, 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 book. 



The time-curve is obviously a fair representation of the 

 progress of the formation of the association, for the two essential 

 factors in the latter are the disappearance of all activity save the 

 particular sort which brings success with it, and perfection of 

 that particular sort of act so that it is done precisely and at will. 

 Of these the second is, on deeper analysis, found to be a part 

 of the first ; any clawing at a loop except the particular claw 

 which depresses it is theoretically a useless activity. If we 

 stick to the looser phraseology, however, no harm will be done. 

 The combination of these two factors is inversely proportional 

 to the time taken, provided the animal surel}^ 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 (£:. ^., 2 in K on page 

 26) 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 our purpose all these matters count little, 

 and we may take the general slope of the curve as representing 

 very fairly the progress of the association. The slope of any 

 particular part of it may be due to accident. Thus, very often 

 the second experience may have a higher time-point than the 

 first, because the first few successes may all be entirely due to 

 accidentally hitting the loop, or whatever it is, and whether the 



