105 



were controlled and a 12 hour light (0700 to 1900 hrs) - dark cycle was 1n 

 effect. 



Apparatus 



Four identical oprant conditioning chambers (Lehigh Valley Electronics Ho. 

 143-25), each contained a sound and light attenuating cubicle (LVE No. 132-02K 

 were used. . On, one wall of the chamber were two levers (LVE No. 121-05), a 



pellet receptacle, six cue lights (lever lights), a speaker and a house light. 



-r -^ _ ^ 



A pellet dispenser delivered one 4S~nigrbod pellet (Bio-Serve) with^ach opera- 



> 



tion. White noise was constantly present in the testing room and an exhaust 

 fan mounted in each cubicle provided ventilation. Programming of experimental 

 contingencies and recording of data were accomplished with the use of solid 

 state logic module digital counter and cumulative recorders located in an 

 adjoining room. . _ • .. i*". 



Procedure 



Rats were tested initially in daily sessions under a fixed ratio 1 (FR 1) 

 schedule for either 60 minutes or until the food pellets were delivered, which- 

 ever occurred first. There was no attempt to hand-shape the lever press 

 response and all rats were responding reliably after a maximum of sexen days. 

 Food pellets were delivered for responses on the left le\ter-only. Responses on 

 the right lever had no programmed consequence but were recorded as a measure of 

 general activity. After 2-3 sessions in which 100 food pellets were 

 delivered under the FR 1 schedule, session duration was decreased to 30 minutes 

 and the FR response requirement was gradually increased over a 2 to 4 week 

 period until an FR 32 schedule was in effect. Responding under the FR 32 

 schedule stabilized after 4 to 6 weeks of testing daily, Monday through Friday. 



