Skinner (1938) was one of the first to report that animals well exposed to the pairing of primary reinforcement, such as food or water, with the sound of a mechanical delivery device (a "magazine"--thus establishing a procedure called "magazine training") was sufficient to train rats to press levers for just the magazine sound alone. Thus it might be expected that this "secondary reinforcement" would result in some degree of bar pressing in trained animals, even though they were not deprived of the reinforcement used for their training. To study both this phenomenon and to accomplish a reasonable measure of time-to-satiety in subsequent experiments where pre-session deprivation of water was used as an establishing operation, we first conducted one "satiation test" session of 60 minutes duration to establish the expected bar press rate during sessions where no pre-session deprivation (i.e., home-cage ad libitum water availability) of the reinforcer had been applied.

For subsequent research on when satiation was reached in extended bar press sessions under deprivation conditions, we applied the criterion of "a continuous 5 minute period where the average bar press rate within that 5 minute window was at or below the average bar press rate for that subject established from the satiation test session." The time of onset for this 5 minute period was then used as the time at which "satiety" had been reached for that animal, regardless of subsequent bar press rates. However, because we had some subjects who met this criteria before any sustained rates of bar pressing had been established (see discussion below concerning session "warm-up/habituation" phenomena and measures), we specifically excluded this period by imposing a "prerequisite" criterion that the "average rate of bar pressing for the entire session had to be reached and/or exceeded prior to application of the satiation criterion."

Subsequent research on CRF under water deprivation establishing operations revealed that it may take some time for a subject to "habituate" to being placed in the opreant chamber, even after significant prior training histories in this environment. This "warm-up" period comes before a steady and sustained rate of bar pressing occurs. We thus calculated the amount of time it took to reach the 5th, 10th, 15th, and finally the 20th bar press to determine the character of this warm-up/habituation period, and these data are reported for the satiation test experiment as well as for subsequent experiments.

---------- Subject A2 --------    ------- Subject A3 -------    --------- Subject A4 ----------

   

Despite being maintained on an ad-libitum schedule of water access, all 3 animals pressed the bar for water between approximately 60 to 90 times across the one hour sessions. Each of the 3 subject's average bar press rates, plus the time elapsed until the 5th, 10th, 15th, and 20th bar press (warm-up period) are reflected in the notes for each graph.

Following this session under no deprivation conditions, we re-established deprivation as setting factor and conducted another series of CRF "maintenance" sessions to assess the rates and rate stability for these same animals. These sessions are reported in the Next Experiment.