156 



BRAIN MECHANISMS AND LEARNING 



o — o— o— o S group 

 (8rats ) 



»--*--»--* F" group 

 ( 7 ra1s ) 



TRIALS 



Fig. 3 

 Runway experiment in which animals ran faster for electric reward 

 (solid line) than a control group running for food (dotted line) (Olds, 

 1956). 



Fig. 4 

 Obstruction box in which animals were required to cross grid 

 with shock to feet to reach pedal to stimulate brain. After three 

 self-stimulations on one side, pedal became inoperable and 

 animal crossed the grid again to get three more selt-stimulations 

 on the other side. Animal continued to shuttle as shock increased 

 until foot shock became so high as to inhibit further self- 

 stimulation behaviour. Foot shock of 60 laamp. stopped most rats 

 running for food; however, one hungry rat took almost 300 

 namp. for food reward. Self-stimulating rats took over 400 

 ijamp. for hypothalamic stimulus as reward. 



