The critical feature in learning is the immediate delivery of a consequence following an appropriate response. (A consequence need not follow every response, but when these consequences occur they should do so immediately after the targeted response.) Over the years a sophisticated technology evolved for such delivery. In the case of laboratory research with animals, this has involved using electrical and electromechanical devices to deliver, most often, food or water precisely. This precision was in the form of both the amount delivered per reinforcement period and the immediacy with which it followed the response. Most research with animals involved automatic control, first by simple electromechanical programming circuitry and more recently by digital computers that record responses and arrange reinforcers according to a program created by the experimenter. As a result, the program can detect the response virtually immediately, determine whether the schedule calls for it to be reinforced and, if so, operate the reinforcement device.
One of the first steps in controlling the reinforcer is to ensure its consistency. With pigeons this is done by presenting access to mixed grain or food pellets for a fixed period of time, as is illustrated with the grain hoppers. The precision of a liquid reinforcer is controlled by presenting pre-measured amounts of the liquid with either a small dipper or by allowing a fixed amount to drain from a reservoir connected to a tube that can be pinched or released electromechanically. Another way of ensuring consistency is to deliver food pellets of a predetermined size through a feeder of the sorts shown in the section on delivery devices for rats.
Reinforcers are not limited to biological events like food and water, of course. Because reinforcers are defined functionally in behavior analysis, in principle almost anything can serve as a reinforcer. As a result, devices were developed to allow the experimenter to dispense a variety of different things as reinforcers, appropriate to the subject or participant and the circumstances of the experiment. These devices were described as universal reinforcer dispensers. Several are featured in this room of the virtual museum.
Delivering Reinforcers to Rats
Delivering Reinforcers to Pigeons
Universal Reinforcer Dispensers