10 JOHN B. WATSON AND MARY I. WATSON 



All the animals being sufficiently automatic in their responses 

 to one stimulus, we decided gradually to introduce the second 

 stimulus. Accordingly both lights were equated in energy. Then 

 the light reacted against was cut down by means of the rotating 

 sector. Table IV shows the results. 



In the case of Rat I and the Rabbit (reacting positively to 

 blue) the introduction of the second stimulus at the energy 

 designated produced no break down in the habit. The associa- 

 tion was maintained fairly well up to the point of equal energy. 

 Rat III (black and white, reacting positively to blue) shows 

 extreme unsteadiness for a time after the energy of the yellow 

 had been increased to one-tenth that of the blue. This may 

 be due to the fact that the yellow possesses slightly more stim- 

 ulating value for him than for the white rats and the rabbit. 

 Consequently the introduction of the yellow (although grad- 

 uated to the same energy values as for the other animals) was 

 for him more abrupt than for them. The records show that 

 after one or two break downs this animal became very steady. 

 The failure of Rat II to discriminate shows, we think, even 

 without further control tests, that yellow has very low stimulating 

 value. Since he was habituated to respond to an intensity value 

 which for him did not lie very high in the scale he was dis- 

 turbed by the blue the moment its intensity equaled that of 

 yellow. This point is reached when the energy of the blue is 

 one-eighteenth that of yellow. All of our tests are in harmony 

 with the view that blue has a tremendously high stimulating 

 value. 



After Rats I and II had learned to discriminate between the 

 lights at equal energies, control tests were introduced for the 

 purpose of finding out whether the discrimination could be 

 held, whatever the energy relations between the two stimuli. 

 On account of the approach of summer, when the tests were to 

 be discontinued we did not gradually cut down intensity of 

 light reacted against as we had previously planned. Instead we 

 chose a variety of tests which we thought would show most 

 rapidly whether the animals were responding to wave length 

 difference or to intensity difference. We give an individual 

 diary record of tests on Rat I. The results of tests on Rat III 

 are quite similar to those reported for Rat I. 



