284 HARVEY CARR 



in the hunger experiment. Both groups of animals reacted to 

 these alterations through a common mode of sensitivity and the 

 percentage affected was the same for both groups. Vision, how- 

 ever, operated to minimize and overcome the effects of the 

 disturbing conditions. The normal animals were able to make 

 more perfect runs; they were able to resist the distracting in- 

 fluences more frequently than the blind rats. When disturb- 

 ances did occur, the normal animals made by far the fewer 

 errors; vision decreased the number of errors. Animals with 

 vision exhibited the greater tendency to adapt themselves to 

 these novel situations; they also recuperated from the effects 

 more quickly after a return to normal conditions. Comparing 

 the records of the two groups in the various experiments of the 

 fourth class, we find that the adaptive and recuperative power 

 of the normals is equal to or greater than that of the blind ani- 

 mals in every case. The normal animals made a greater per- 

 centage of perfect runs with the exception of one experiment; 

 evidently they are more able to resist the distractive conditions. 

 Rats with vision gave the smaller error score in every experiment 

 but one; they thus possess the power of minimizing the disturb- 

 ance when it occurs. When comparisons are possible as to the 

 correlation between the maximum disturbance and the dura- 

 tion of exposure to the novel conditions, we find that the normal 

 animals are the more resistant in three of four cases. The 

 blind rats invariably exhibit the greater variability as to the 

 range of errors. Blind rats are extremely variable as to num- 

 ber of errors; they are more likely to go to pieces, become lost 

 and run high error scores when they are disturbed; this fact 

 would indicate that vision operates as a corrective and control. 

 The discrepancies and exceptions in the application of the 

 above two principles of explanation become explicable when we 

 consider that the two functions of sensitivity and adaptation 

 are antagonistic in their effects. The greater the sensitivity the 

 larger will be the number of animals affected, the percentage of 

 runs with error, and the total number of errors. The corrective 

 function will operate to decrease the number of errors and the 

 percentage of runs with error; it might also decrease the number 

 of animals susceptible to the disturbing changes. The two func- 

 tions, although antagonistic in their effects, are not necessarily 

 mutually exclusive; both may conceivably operate at the same 



