Almost all traditional animal training consists of the applied use of negative reinforcers. The horse learns to turn left when the left rein is pulled, because by doing so it can ameliorate the tugging feeling in the left corner of it's mouth. Elephants, oxen, camels, and other beasts of burden learn to move forward, halt, pull loads, and so on to avoid the tug of a halter, the poke or blow of a prod, goad, or whip.
Negative reinforcement can be used to shape behavior. As with positive reinforcement, the reinforcer must be contingent upon the behavior: one must cease "prodding" when the response is correct. Unfortunately, because the prodding, in whatever form results in a change in behavior, the behavior of the person doing the prodding may be positively reinforced, so that, as with punishing, the tendency to lay on with the aversives increases. Naggers, for example, may eventually get results, and this is reinforcing to the nagger. So nagging escalates, sometimes so much that the nagger goes on nagging whether the desired response has occurred or not. Think of the mother in Portnoy's Complaint, who complains, while her son is visiting, "We never see you!"
Positive and Negative reinforcement contingencies are often reciprocal. Behaviorist Myrna Libby, Ph.D., gave me this example: child is tantruming in the store for candy. The parent gives in and lets the child have a candy bar. The tantrum is positively reinforced by the candy, but the more powerful event is that the parent is negatively reinforced for giving in, since the public tantrum, so aversive and embarrassing for the parent, actually stopped.
Tantrums can become part of a vicious circle. The parent will go to all kinds of lengths-soothing, protesting, arguing, and reinforcing- to stop a tantrum. So the tantrums escalate, and because they do, the parent's inadvertently reinforcing efforts escalate as well. I know of one household in which a child threw a full-blown, fifteen-or twenty-minute screaming tantrum nearly every night, just at dinnertime. Both the child's behavior and the parents' anxious responses were so strongly maintained, by interlocking positive and negative reinforcements, that the behavior continued for over three years.
People use spontaneous negative reinforcers on each other all the time: The warning glance, the frown, the disapproving remark. Some children's lives, and some spouses' lives too, are filled with constant daily effort to behave in such a way as to avoid disapproval. The overpunished child may become hostile, evasive and a punisher himself in adulthood. In contrast, the child that grows up striving, not to please, exactly, but to bring a halt, if only temporarily to chronic disapproval, may become timid, self-doubting, and anxious in adult life. A therapist specializing in phobic patients tells me that her clientele, with their crippling irrational fears of crowds or elevators, were all raised on a steady diet of negative reinforcement.
However, because negative reinforcers are aversive-something the subject wants to avoid-every instance of their use contains a punisher. Pull on the left rein, and you are punishing going straight ahead, as well as negatively reinforcing turning to the left when that occurs. The traditional trainer typically doesn't think of his negative reinforcers-his reins or choke chains or verbal corrections-as punishment. After all, trainers explain these tools are gently used, on the whole: if the trainer really wanted to punish, there are much more severe corrections available. And, the argument typically continues if you use a lot of praise and positive reinforcers as well, no harm is done in the long run.
However, the strength of the aversive can only be judged by the recipient. What the trainer may consider to be mild may be seen by the trainee as blisteringly severe. Furthermore, since all negative reinforcement, by definition, includes a punisher, making a practice of using negative reinforcement puts you at risk for all the unpredictable fallout of punishment: avoidance, secrecy, fear, confusion, resistance, passivity, and reduced initiative, as well as spillover associations, in which anything that happens to be around, including the training environment and the trainer, becomes distasteful or disliked, something to be avoided or even fled from.
Because training with negative reinforcers or correction is the traditional and conventional system, the resulting fallout is extraordinarily obvious once you look for it. I have attended national level dog obedience competitions and been startled by the glum faces, unwagged tails, and cautious, inhibited movements of many of the top-level performance dogs. Go to any riding academy or horseback event, and ask yourself if the horses look cheerful. Most people, even professional equestrians, and even those that consider themselves to be modern and humane trainers, don't know what a happy-eyed horse looks like. They've never seen one.