292 HARVEY CARR 



2. The distractions and resulting errors induce confusion and 

 excitement, and this confusion may now operate as a further 

 distraction. Adaptation is a process of minimizing and allay- 

 ing this excitement, and all familiar or unaltered stimuli will 

 possess this quieting and reassuring characteristic. Adaptation 

 is a matter of learning to direct the attention to the familiar 

 aspects of the environment. Rats with vision will have an 

 advantage because of their greater learning capacity and their 

 greater sensory contact with the environment. 3. The disturb- 

 ances are due to distracting stimuli, and adaptation is a pro- 

 cess of strengthening the maze habit up to a point where it is 

 immune to the distractive effects of those particular stimuli. 

 Adaptation is thus a further process of learning, and those ani- 

 mals with the greater learning capacity will manifest the greater 

 adaptive power. On this assumption the adaptive capacity of 

 normal rats will be greater than that belonging to blind animals. 

 4. Blind rats are less resistant to distractions because of the 

 operative effects. As previously noted, these effects may be 

 conceived as intraorganic distractive stimuli of some sort, or as 

 nervous conditions conducing to exaggerated and erratic re- 

 sponses. Blind rats will be regarded as essentially unstable 

 organisms, subnormal in their capacity of resisting distracting 

 stimuli. 5. Adaptation may be conceived as a process of de- 

 creasing sensory susceptibility to stimuli due to neural or end 

 organ changes somewhat akin to fatigue. On this hypothesis 

 any end organ can adapt only to those alterations which were 

 sensed by that receptor. 



The factual data are insufficient for any very confident judg- 

 ments as to the relative validity of these various hypotheses. 

 The normal animals manifested by far the greater adaptive 

 power; this fact is readily explicable in terms of any one of the 

 first four conceptions. The difference of adaptive capacity of 

 the two groups is generally greater than their differences in 

 learning ability as manifested in the mastery of the maze; this 

 fact militates against the 1st and 3rd conceptions as complete 

 explanations of adaptation. The first conception must be sum- 

 marily dismissed as the facts indicate rather conclusively that 

 extraneous stimuli do not function as motor controls after the 

 maze is mastered. The greater variability of the blind rats 

 may be explained on the basis of either the 2nd or the 4th hy- 

 potheses. The immunity to distractions due to adaptation is 



