|An Animal Trainer's Introduction To |
Operant and Classical Conditioning Part II
By: Stacy Braslau-Schneck, MA
This is possibly the easiest, most effective consequence for a trainer to control (and easy to understand, too!). Positive reinforcement means starting or adding Something Good, something the animal likes or enjoys. Because the animal wants to gain that Good Thing again, it will repeat the behavior that seems to cause that consequence.
The dolphin gets a fish for doing a trick. The worker gets a paycheck for working. The dog gets a piece of liver for returning when called. The cat gets comfort for sleeping on the bed. The wolf gets a meal for hunting the deer. The child gets dessert for eating her vegetables. The dog gets attention from his people when he barks. The elephant seal gets a chance to mate for fighting off rivals. The child gets ice cream for begging incessantly. The toddler gets picked up and comforted for screaming. The dog gets to play in the park for pulling her owner there. The snacker gets a candy bar for putting money in the machine.
Secondary positive reinforcers and Bridges
A primary positive reinforcer is something that the animal does not have to learn to like. It comes naturally, no experience necessary. Primary R+s usually include food, often include sex (the chance to mate), the chance to engage in instinctive behaviors, and for social animals, the chance to interact with others.
A secondary positive reinforcer is something that the animal has to learn to like. The learning can be accomplished through Classical Conditioning or through some other method. A paycheck is a secondary reinforcer - just try writing a check to reward a young child for potty training!
Animal trainers will often create a special secondary reinforcer they call a bridge. A bridge is a stimulus that has been associated with a primary reinforcer through classical conditioning. This process creates a conditioned positive reinforcer, often called a conditioned reinforcer or CR for short. Animals that have learned a bridge react to it almost as they would to the reward that follows (animals that have learned what clicker training is all about may somethings prefer the CR that tells them they got it right to the actual "reward").
Schedules of Reinforcement, and Extinction
A schedule of reinforcement determines how often a behavior is going to result in a reward. There are five kinds: fixed interval, variable interval, fixed ratio, variable ratio, and random.
A fixed interval means that a reward will occur after a fixed amount of time. For example, every five minutes. Paychecks work on this schedule - every two weeks I got one.
A variable interval schedule means that reinforcers will be distributed after a varying amount of time. Sometimes it will be five minutes, sometimes three, sometimes seven, sometimes one. My e-mail account works on this system - at varying intervals I get new mail (for me this is a Good Thing!).
A fixed ratio means that if a behavior is performed X number of times, there will be one reinforcement on the Xth performance. For a fixed ratio of 1:3, every third behavior will be rewarded. This type of ratio tends to lead to lousy performance with some animals and people, since they know that the first two performances will not be rewarded, and the third one will be no matter what. Some assembly-line production systems work on this schedule - the worker gets paid for every 10 widgets she makes. A fixed ratio of 1:1 means that every correct performance of a behavior will be rewarded.
A variable ratio schedule means that reinforcers are distributed based on the average number of correct behaviors. A variable ratio of 1:3 means that on average, one out of every three behaviors will be rewarded. It might be the first. It might be the third. It might even be the fourth, as long as it averages out to one in three This is often referred to as a variable schedule of reinforcement or VSR (in other words, it's often assumed that when someone writes "VSR" they are refering to a variable ratio schedule of reinforcement).
With a random schedule, there is no correlation between the animal's behavior and the consequence. This is how Fate works.
If reinforcement fails to occur after a behavior that has been reinforced in the past, the behavior might extinguish. This process is called extinction. A variable ratio schedule of reinforcement makes the behavior less vulnerable to extinction. If you're not expecting to gain a reward every time you accomplish a behavior, you are not likely to stop the first few times your action fails to generate the desired consequence. This is the principle that slot machines are based on. "OK, I didn't win this time, but next time I'm almost sure to win!"
When a behavior that has been strongly reinforced in the past no longer gains a reinforcement, you might experience what's call an extinction burst. This is when the animal performs the behavior over and over again, in a burst of activity. Extinction bursts are something for trainers to watch out for!
See some nice graphs of various schedules here (but skip the table of "Outcomes of Conditioning" - it's misleading. This author uses "positive" to mean both "added" and "nice" - confusing!)
Recently Bob Bailey has cautioned against needlessly using variable schedules. Most useful behaviors, he points out, will get some sort of reinforcement every time. You might not always click and treat your dog for sitting on cue, but you will always reward it with some recognition and praise ("Good dog!"). If there is some circumstances where you will be unable to deliver any reinforcement (during a long sequence of behaviors, or when the animal is out of contact), then you will need to build a buffer against extinction with a VSR. Otherwise, don't bother.
Cautions in using positive reinforcement
If the animal is acting out of fear, you may be rewarding the fear response. This can happen when you coddle a shy dog.
The timing must be good. If the animal did a great "stay" and you reward after the release, you are rewarding getting up.
The reward has to be sufficient to motivate a repetition. Mild praise won't be enough for some animals. Others require the richest of food rewards, etc.
Reinforcements can become associated with the person giving them. If the animal realizes that he can't get any rewards without you present, he will not be motivated to act.
Animals can get sated with the reward you're offering when they've had enough, and it will no longer be motivating.
Reinforcers incrase behavior. If you don't want your animal actively traying out new behaviors ("throwing behaviors at the trainer"), don't use positive reinforcement. Use a positive reinforcement to train an animal to do something.
Negative punishment is reducing behavior by taking away Something Good. If the animal was enjoying or depending on Something Good she will work to avoid it getting taken away. They are less likely to repeat a behavior that results in the loss of a Good Thing. This type of consequence is a little harder to control.
The child has his crayons taken away for fighting with his sister. The window looking into the other monkey's enclosure is shut when the first monkey bites the trainer. "This car isn't getting any closer to Disneyland while you kids are fighting!" The dog is put on leash and taken from the park for coming to the owner when the owner called (this causes the unintentional result of the dog being less likely to respond to the recall). The teenager is grounded for misbehavior. The dolphin trainer walks away with the fishbucket when the dolphin acts aggressive. "I'm not talking to you after what you did!" Xena cuts off the air of an opponent until he tells her what she wants.
Secondary Negative Punishers
Trainers seldom go to the trouble of associating a particular cue with negative punishment. It's sometimes called a "delta", from SD or discriminative stimulus. Some dog owners make the mistake of calling their dogs in the park and then using the negative punishment of taking the dog away from the fun. "Fido, come!" then becomes a conditioned negative punisher. My mom conditioned a similar CP- as "Time to go!".
Positive punishment is something that is applied to reduce a behavior. The term "positive" often confuses people, because in common terms "positive" means something good, upbeat, happy, pleasant, rewarding. Remember, this is technical terminology we're using, though, so here "positive" means "added" or "started". Also keep in mind that in these terms, it is not the animal that is "punished" (treated badly to pay for some moral wrong), but the behavior that is punished (reduced). Positive punishment, when applied correctly, is the most effective way to stop unwanted behaviors. Its main flaw is that it does not teach specific alternative behaviors.
Our society seems to have a great fondness for positive punishment, in spite of all the problems associated with it (see below). The peeing on the rug (by a puppy) is punished with a swat of the newspaper. A dog's barking is punished with a startling squirt of citronella. The driver's speeding results in a ticket and a fine. The baby's hand is burned when she touches the hot stove. Walking straight through low doorways is punished with a bonk on the head. In all of these cases, the consequence (the positive punishment) reduces the behavior's future occurences.
Secondary Positive Punishers
Because a positive punisher, like other consequences, must follow a behavior immediately or be clearly connected to the behavior to be effective, a secondary positive punisher is very important. (This is especially true if the punisher is going to be something highly aversive or painful). Many dog trainers actively condition the word "No!" with some punisher, to form an association between the word and the consequence. The conditioned punisher (CP+) is an important part of training with Operant Conditioning.
Cautions in using Positive Punishment
Behaviors are usually motivated by the expectation for some reward, and even with a punishment, the motivation of the reward is often still there. For example, a predator must face some considerable risk and pain in order to catch food. A wild dog must run over rough ground and through bushes, and face the hooves, claws, teeth, and/or horns of their prey animals. They might be painfully injured in their pursuit. In spite of this, they continue to pursue prey. In this case, the motivation and the reward far outweigh the punishments, even when they are dramatic.
The timing of a positive punishment must be exquisite. It must correspond exactly with the behavior for it to have an effect. (If a conditioned punisher is used, the CP+ must occur precisely with the behavior). If you catch your dog chewing on the furniture and you hit him when he comes to you, you are suppressing coming to you. The dog will not make the connection between the punishment and the chewing (no matter how much you point at the furniture).
The aversive must be sufficient to stop the behavior in its tracks - and must be greater than the reward. The more experience the animal has with a rewarding consequence for the behavior, the greater the aversive has to be to stop or decrease the behavior. If you start with a small aversive (mild electric shock or a stern talking-to) and build up to a greater one (strong shock or full-on yelling), your trainee may become adjusted to the aversive and it will not have any greater effect.
Punishments may become associated with the person supplying them. The dog who was hit after chewing on the furniture may still chew on the furniture, but he certainly won't do it when you're around!
Physical punishments can cause physical damage, and mental punishments can cause mental damage. You should only apply as much of an aversive as it takes to stop the behavior. If you find you have to apply a punishment more than three times for one behavior, without any decrease in the behavior, you are not "reducing the behavior", you are harassing (or abusing) the trainee.
Punishers suppress behaviors. Use positive punishment to train an animal not to do something.
Negative reinforcement increases a behavior by ending or taking away Something Bad or aversive. By making the animal's circumstances better, you are rewarding it and increasing the likelihood that it will repeat the behavior that was occurring when you ended the Bad Thing.
In order to use negative reinforcement, the trainer must be able to control the Bad Thing that is being taken away. This often means that the trainer must also apply the Bad Thing. And applying a Bad Thing might reduce whatever behavior was going on when the Bad Thing was applied. And reducing a behavior by applying a Bad Thing is positive punishment. So when you start your Bad Thing that you're going to end as a negative reinforcer, you run the risk of punishing some other behavior.
One of the major results of taking away Something Bad is often relief. So another way to think of negative reinforcement is that you are providing relief to the animal but of course, this makes it an example of positive reinforcement - you are providing Something Good - relief. Confusing?
The choke collar is loosened when the dog moves closer to the trainer. The ear pinch stops when the dog takes the dumbbell. The reins are loosened when the horse slows down. The car buzzer turns off when you put on your seatbelt. Dad continues driving towards Disneyland when the kids are quiet. "I'm not talking to you until you apologize!" The hostage is released when the ransom is paid. The torture is stopped when the victim confesses. "Why do I keep hitting my head against the wall? 'Cause it feels so good when I stop!" The baby stops crying when his mom feeds him.
Secondary Negative Reinforcers
Trainers seldom go to the trouble of associating a particular cue with negative reinforcement. You can still go ahead and do it.
Internal Reinforcers and Punishers
Trainers can not control all reinforcers and punishers, unfortunately. There are a number of environmental factors that are going to affect the animal's behavior that you have no control over, but which will still be a significant consequence for your trainee.
Some of these come from the animal's internal environment - their own reactions. Relief from stress, pain, or boredom are common reinforcers and some "self-reinforcing" behaviors are actually maintained because of this. Examples are a dog barking because it relieves boredom, or a person chewing on her fingers or smoking a cigarette because it relieves stress. Drivers speed because it is fun. Guilt is an internal punisher that some people experience.
"No Reward Markers" and "Keep Going Signals"
There's actually a fifth possible consequence to any behavior: nothing. You push the button and nothing happens. You raise your hand and the teacher doesn't call on you. You get no response to your e-mail, your proposal, or your job application. The question you then have is, did no one notice your behavior? Or was it just not worthy of a reinforcement?
To differentiate between these two possibilities, a trainer can use a no reward marker (NRM). The NRM tells the animal that its behavior will not gain it a reinforcer. A lot of dog trainers use "Nope!" "Wrong!" "Uh-uh!" or "Try again" as NRMs. For example, if you're teaching your dog to sit in response to the cue "sit" (it's not as obvious to the dog as it is to you; after all, dogs don't have the experience of verbal words being labels for actions), and the dog lies down or barks, you can give a NRM. The purpose of the NRM is to get the animal to try something different. It is not a conditioned punisher and should not be used when the dog does something you don't want it to ever do. It's for when a behavior might be correct in a different circumstance but not in this one.
Some trainers also have developed a keep going signal (KGS). This signal tells the animal that it's on the right track, that its behavior is leading to something that will gain it a reinforcer. For example, if you're teaching a dog to roll over and it will lie on its side, you can use a KGS to tell it that it's close to a behavior that will get it a reward, but not there yet. Read more on the KGS here.
Reprinted by permission
Stacy Braslau-Schneck, CPDT