The Maintenance of Behavior by the Termination and Onset of Intense Noise1

The purposes of the present investigation were, first, the establishment of the strength and temporal distribution of responses maintained by the termination and onset of a noise; and, secondly, the isolation of some of the variables which control such behavior. METHOD Subjects and apparatusForty-two white rats were used in this experiment.The apparatus consisted of a lightproof and sound-resistant box containing a rat lever (Gerbrands) and a source of sound ("tweeter" loudspeaker).An essential feature of this equipment was a wire-mesh cage placed in the center of the larger box.The purpose of the wire-mesh cage was to insure that the animal was restricted within a uniform sound field.Preliminary experiments showed that the intensity of the sound rose sharply in the vicinity of the inner walls of the box, a possible factor in keeping the animal away from a lever mounted close to or through a wall.The sound consisted of a signal containing all frequencies between 500 and 20,000 cycles per second.Sound intensities were measured by an H. H. Scott sound level meter, the microphone of which was placed in the vicinity of the lever at about the same height above the floor as the rat's head.Measurements were taken at other locations within the wire-mesh enclosure, and little variation in intensity was found.Intensities between 108 and 116 decibels were used.The sound signal was switched at the output of the amplifier to minimize switch- ing transients.During the time the sound was off the loudspeaker was short- circuited to prevent it from picking up any impulses from relay operation during this period.Unless otherwise stated, the switching of the sound signal was as rapid as the operation of the appropriate relay contacts.Further technical details will be found elsewhere (Barry & Harrison, 1957; Harrison & Tracy, 1955).Two operants, Rp (the depression of the lever) and RR (the return of the lever to its normal position), were used in this experiment.Two schedules were used.In the first, the escape schedule of Keller (1941), an occurrence of RP in the presence of sound was followed by three events: (1) the termination of the sound: (2) the initiation of a time interval, Ts (silent period); and (3) the restoration of the sound at the end of the time interval.An occurrence of Rp during the silent period was without effect on the animal's environment.An occurrence of RR was also without experimental contingency.Rate of escape re- sponding was obtained by dividing the total number of escape responses (i.e., Rp in presence of sound) by the total time the sound was on during the session.