ABSTRACT
A great deal of work has gone into the study of the effects of the various possible schedules of reinforcement on the behaviour of lower organisms. In the variable-ratio schedule, the number of responses that must be emitted before reinforcement is administered is allowed to vary around an average value. Experiments with lower organisms have shown that reinforcements have a greater effect in strengthening responses the more closely they follow the responses in time. Standard electrical devices also controlled the presentation of the reinforcements. All were reinforced with a mixture of candy and cigarettes on a one-minute variable-interval schedule of reinforcement. O. R. Lindsley has used the expression "conjugate reinforcement" to describe the way in which the intensity of the continuously available reinforcing stimuli may be made to vary directly and immediately with the rate of responding in this kind of situation.
