A second primary objective for training dogs is to reduce or suppress the fre-quency of undesirable behaviour. Pet dog owners find themselves faced with a myriad of normal, yet objectionable dog behaviours: dogs bark at inappropriate times, urinate on the furniture, pull on the leash, barge out the front door and growl at strangers. Working dogs also display behaviours that interfere with suc-cessful performance of their tasks. Herding dogs bite their charges; retrieving dogs run off with the game; agility dogs are so keen that they leave obstacles prema-turely; and guide dogs lead their owners too close to moving traffic. Some type of punishment, whether positive or negative, may be required to eliminate such problematic behaviour.
In this section, I outline the general processes by which dogs inhibit instru-mental behaviour for the purpose of escaping or avoiding an unpleasant outcome, in other words, learning by punishment. The stimuli used to motivate such learn-ing are the same as for learnlearn-ing by reinforcement: appetitive and aversive stimuli.
However, negative punishment can result from the cessation or prevention of appetitive stimuli; and positive punishment can result from the threat or presen-tation of aversive stimuli. I also include a procedure called extinction that is not punishment but still functions to produce a decline in behaviour.
Extinction
Extinction involves the discontinuation of reinforcement for a conditioned behav-iour. As such, any associative learning, whether operant or classical, can be subject to extinction. However, the most common application of extinction is to cease reinforcement, whether intentional or adventitious, of established operant behaviour. For instance, imagine the pet dog owner who, quite innocently, teaches the dog to whine to be released from confinement. Initially, the dog whines from the distress of separation. The owner releases the dog and whining is negatively reinforced with escape from an unpleasant situation. Eventually the
dog learns to whine relentlessly whenever it is placed in confinement until the owner breaks down and releases it. If the owner commits to ignoring the dog when it whines, in other words, omitting the reinforcement, whining will extin-guish.
The goal of extinction is to reverse the effects of acquisition. Extinction does indeed lead to a gradual decline in the frequency of a conditioned behaviour. The confined dog gradually, over time, whines less. However, the first effect of extinc-tion is that the behaviour becomes more variable (Neuringer et al., 2001). Maybe the dog tries barking, scratching or digging. Nonreinforcement produces frustra-tion and frustrafrustra-tion typically energizes behaviour (Amsel, 1962). Whining may actually increase beyond previous levels, called an extinction burst. Frustration also produces strong emotional responses, such as aggression (Azrin et al., 1966). If a second animal is present, extinction-induced aggression may be directed toward the innocent third party or toward the owner.
One of the hallmark effects of extinction is spontaneous recovery (Rescorla, 1997). Suppose the dog ceases whining and is released from confinement. The next time the dog is placed in confinement, whining resumes for a while.
Recovery of the response is rarely complete and extinction occurs more rapidly than the first time. With each subsequent period of confinement, the extent of spontaneous recovery diminishes. The occurrence of spontaneous recovery can be devastating to a dog owner. Other recovery effects can also cause a restoration of the unwanted behaviour. Confine the dog in a different environment and whining is likely to emerge; this is called renewal of the response. Renewal occurs because extinction was linked to the contextual cues present in the original situa-tion (Bouton and King, 1983). Exposing the dog to the reward of being released from confinement, or even the stimuli leading up to the reward, such as attend-ing to the dog, can also prompt resumption of whinattend-ing. This is called reinstatement (Bouton, 1994).
Yet another potential limitation of extinction is the partial reinforcement extinc-tion effect. Prior to extincextinc-tion, the condiextinc-tioned behaviour was reinforced on either a continuous or an intermittent schedule. Behaviours with an intermittent rein-forcement history extinguish much more slowly than behaviours with a continu-ous reinforcement history (Jenkins and Stanley, 1950). Think of how long the string of losses would need to be for a habitual gambler to stop playing the slot machines! Extinction that follows partial reinforcement also produces fewer frus-tration responses. Resistance to extinction can also be beneficial. Desirable behaviours that have been maintained on partial reinforcement are likewise resistant to extinction. Dogs can be expected to perform reliably in the competi-tion ring where tangible reinforcement is prohibited, if the training incorporated intermittent reinforcement.
Instituting extinction is a popular procedure for reducing unwanted behav-iour because it does not involve the use of aversive stimuli. However, there are so many variables prompting restoration of the behaviour that the practical value of extinction is extremely limited.
Negative punishment
Negative punishment can be used to discourage or suppress unwanted behaviour in cases where the animal is anticipating a pleasant outcome. When the unwanted behaviour occurs, delivery of the appetitive stimulus is prevented or, if the appet-itive stimulus has already been presented, occurrence of the unwanted behaviour causes withdrawal of the appetitive stimulus. Suppose an owner wants the dog to cease jumping up to greet them upon their arrival home after an absence. The dog jumps up in anticipation of a friendly reunion. If, instead, the owner turns away and ignores the dog for a period of time, the anticipated reward is withheld.
This is an application of negative punishment and one would expect the likeli-hood of jumping up to diminish.
Negative punishment sounds a lot like extinction but it is distinctly different.
Extinction occurs when a previously reinforced behaviour no longer produces reinforcement. In the case of negative punishment, there is no requirement that the behaviour be reinforced previously. The essence of negative punishment is that when the unwanted behaviour occurs, sources of reinforcement are withheld for some period of time. In most applications of negative punishment, it is commonly referred to as time out. In some cases, only the existing reinforcement is withheld; in other cases, all sources of reinforcement are removed. For instance, arranging for the dog owner to turn away from the dog when it jumps up prevents the dog from enjoying a social greeting. However, removing the dog to a small area of confine-ment, with no access to alternative activities, temporarily restricts the dog from all potential sources of reinforcement. While we might assume that removal from all sources would be more effective, sometimes it is difficult to achieve because the act of moving the dog to an isolation area can be problematic and, once there, dogs are adept at finding ways to entertain themselves with other undesirable behaviour (chewing, digging, barking, etc.). In general, short time-out durations of a few seconds to a minute or two are effective (Lindsay, 2000). Longer time out periods do not increase effectiveness (White et al., 1972).
The use of time out to eliminate unwanted behaviour during controlled situations, such as training sessions, can be extremely effective, provided the dog finds training pleasurable. For instance, a savvy trainer ignores the dog for a second or two when the dog barks rather than performing the requested behaviour, another trainer requires that the agility dog lie down for a moment after performing an obstacle incorrectly, and still another trainer sends the dog into its crate after an infraction so that it must wait while the trainer works another dog. However, it should be clear that these examples of time out would not be appropriate for a dog that would prefer to avoid training!
Like extinction, time out is an appealing technique for reducing unwanted behaviour because it does not involve the use of aversive stimuli. A few studies have contrasted the effectiveness of extinction and negative punishment with positive punishment, suggesting that: (i) negative punishment is more effective than extinc-tion in suppressing unwanted behaviour; and (ii) negative punishment takes longer than positive punishment to reduce the frequency of unwanted behaviour and that suppression is rarely complete (Uhl and Sherman, 1971).
Positive punishment
Positive punishment is the presentation of an aversive stimulus, contingent upon the occurrence of an unwanted behaviour. If the procedure is effective, the unwanted behaviour should decrease in frequency or be eliminated altogether.
For example, suppose an owner wants to discourage the dog from getting up on the couch. The owner could watch the dog carefully and each and every time the dog jumps on the couch, the owner loudly shakes an aluminium can filled with pebbles. After a few attempts, the dog learns that the way to avoid hearing the noxious sound is to stay clear of the couch. Learning curves are often steeper with positive punishment than with other operant conditioning procedures. Positive punishment can produce dramatic suppression of behaviour in just a few repeti-tions (Domjan, 2003).
Much of the research on positive punishment has been devoted to delineat-ing its use. In general, positive punishment leads to more effective suppression of behaviour when these conditions are met:
● The more intense and/or long lasting the aversive stimulus, the more behav-ioural suppression (low intensity aversive stimulation produces only moderate suppression and eventual response recovery) (Azrin, 1960).
● An aversive stimulus introduced at high intensity is more effective than if ini-tially presented at low intensity and then increased (animals become resistant to the effects of the aversive stimulus if it is initially presented at low intensity; con-versely experience with high intensity aversive stimulation increase the effec-tiveness of later low intensity aversive stimuli) (Azrin and Holz, 1966).
● Even response-independent positive punishment can lead to some suppression, but response-dependent positive punishment is significantly more effective (in other words, exposure to an aversive stimulus, whether contingent on behav-iour or not, leads to some dampening down of all instrumental behavbehav-iour) (Church et al., 1970).
● Immediate punishment (both negative and positive) is more effective than delayed punishment (Camp et al., 1967).
● The degree of suppression produced by positive punishment is a direct function of the number of responses punished (intermittent punishment can work, but not as effectively as a continuous schedule of punishment) (Azrin, 1956).
Positive punishment is more effective when the animal is provided with other appropriate activities for obtaining reinforcement (Herman and Azrin, 1964). For instance, a dog jumps on the couch for the reinforcement of a soft place to lie down. If the dog is provided with its own comfortable resting area, punishing the dog for getting on the couch is more likely to work than if the dog has no alter-native for obtaining the reinforcement. If a discrimialter-native stimulus signals that positive punishment is in effect, the animal will learn to suppress behaviour only in the presence of that SD(Dinsmoor, 1952). If the dog is only punished for getting on the couch when the owner is home, the dog will only learn to refrain from getting on the couch when the owner is present.
The use of positive punishment (and negative reinforcement), because they entail aversive stimuli, is highly controversial. This issue is not whether positive punishment works; there is no question that the aversive control of behaviour is effective. The concern is whether the use of positive punishment is ethical, espe-cially for animals, because they cannot consent. When deciding whether the ben-efits of positive punishment warrant its use, there are numerous factors to be considered, including the expertise of the trainer, the seriousness of the unwanted behaviour, the urgency of the need for behaviour change, and the quality of life of the dog and of the humans coming into contact with the dog. Another concern is that the line between positive punishment and abuse can be unintentionally crossed, both by pet owners and skilled professionals. Indeed, dog-training texts dating pre-1990s are peppered liberally with techniques that waver along that line, such as scruff shakes, alpha rolls, severe collar corrections, hanging and heli-coptering (e.g. Saunders, 1946; Koehler, 1962; Strickland, 1965; Monks of New Skeet, 1978; Brown, 1983). Fortunately, as dog trainers become well versed in learning theory, more humane applications are being developed. While it is outside the scope of this chapter to explore the controversy in detail, let me suggest that animal care professionals comply with the principle of the least aver-sive alternative: that the least averaver-sive technique that is reasonably expected to succeed should be the technique of choice (Delta Society, 2001). Adherence to this principle will at least give pause for thought and, hopefully, people will err on the side of humane treatment.