INSTINCTS AND HABITS IN CHICKS 



31 



on that date. Twelve of no. 58's striking reactions were at one 

 particle. It followed this up, hitting it time after time until the 

 grain was knocked off the table. 



The final test of social influence in its relation to pecking 

 was made on two comparable groups of six chicks each, which 

 will be referred to as Group E and Group F. The chicks of Group 

 E were hatched on Dec. 2, 1908; those of Group F on Dec. 12, 

 1908. The members of Group F, thus ten days younger, were 

 transferred from the incubator to the cages and brooder occu- 

 pied by Group E. Records were taken as before. Still greater 

 precaution was observed as to food supply. The food was not 



50 



Oiya 1 2 3 4 5 6 7 S 9 10 U 12 13 r4 IS 16 17 IS 19 20 21 S 23 24 25 



Figure 4 — A comparison of curves of development of the pecking instinct to show 

 the possible effect of social influence. Distances along axis of abscissae repre- 

 sent days of age ; distances along axis of ordinates, the number of a given type 

 of reaction in a daily series of fifty pecking reactions. Curves III-E and Ill-F 

 show respectively the rate of decrease in the number of reaction 3 for Groups 

 E and F; Curves IV-E and IV-F show the improvement in accuracy of reac- 

 tion 4 for the same groups. 



unnecessarily stinted, however. The chicks chirped loudly when 

 I came into the room in the morning and crowded toward me 

 when I approached the side of the brooder. In the tests they 

 picked up the grains very energetically. 



The records for Group E are given in full in table 5 , the sum- 

 mary for Group F in table 6. The curves for reactions 3 and 

 4 of both groups are plotted in fig. 4; for reactions i and 2 in 

 fig. 5. The efficiency of the pecking of the older group is repre- 

 sented numerically by 42.2 on a scale of 50 on their eleventh 

 day, when the chicks of Group F entered the cage. The twelve 

 chicks were confined in the brooder each evening together, were 



