HABIT FORMATION IN THE ALBINO RAT 51 



it and continually rising. In other words, final efficiency de- 

 creases rather than increases when practice is continued. An 

 interesting point is that errors will be made even after the prob- 

 lem is learned. Of the six rats used, three made errors in the 

 first test of six trials after the problem was learned, one in the 

 second test, and one not until the fifth test. Errors increased 

 as the work was continued. During the last half of the one 

 hundred sixty additional trials twice as many errors were made 

 as in the first half. 



A closer examination of the table shows: First, that the 

 best record in each case was made during the first fourteen 

 tests; Second, that the last test was better than the first in 

 only one case (rat 15) ; Third, that rats fourteen and fifteen 

 probably had not reached their efficiency level during the learn- 

 ing process, while the other rats had. This fact is deduced 

 from the number of times each rat made a record lower than 

 its absolute time record. 



Rat 8 9 times out of 28 



Rat 12 8 times out of 28 



Rat 14 21 times out of 28 



Rat 15 14 times out of 28 



Rat 16 2 times out of 28 



Rat 17 3 times out of 28 



BLOOD RELATIONSHIP AND LEARNING 



It was found that the learning ability of certain members 

 of a group could be predicted from the results obtained on other 

 members of the same litter. The data appear in Table XII. 

 Three rats from the Y(CF) litter were used when twenty-five 

 days old, and five rats from the same litter worked when sixty- 

 five days old. Two members of the GJ litter learned the prob- 

 lem at twenty-five days, and one at sixty-five days. Two AL 

 rats worked when twenty-five days old, and one when sixty-five 

 days old. Four XL rats learned the problem at twenty-five 

 days, three at sixty-five days and three at two hundred days. 



The rats belonging to the Y(CF) litter required a smaller 

 number of trials at twenty-five days than the average, but 

 their absolute time, total time and total distance were above 

 the average for rats of that age. At sixty-five days, rats of the 

 same litter made averages higher than the group averages for that 



