punishment in horse-training and the concept of ethical equitation
TRANSCRIPT
Address repr
ulty of Veterina
2006, Australia.
E-mail: paul
1558-7878/$ -se
doi:10.1016/j.jv
Journal of Veterinary Behavior (2009) 4, 193-197
ROUNDTABLE/CURRENT TOPICS IN DISCUSSION
Punishment in horse-training and the concept of ethicalequitation
Paul D. McGreevy, BVSc, PhD, MRCVS, MACVSc (Animal Welfare)a,Andrew N. McLean, BSc, PhDb
aFrom the Faculty of Veterinary Science, University of Sydney, Sydney, NSW 2006, Australia; and thebAustralian Equine Behaviour Centre, Broadford, VIC 3658, Australia.
KEYWORDS: Abstract By definition, punishment makes a response less likely in the future. Because horses are
conditioning;welfare;ethical equitation;horse;punishment;
traininglargely trained by negative reinforcement, they are susceptible to inadvertent punishment. Delays inthe release of pressure can make desirable responses less likely and thus punish them. This study ex-amines the correct use of negative reinforcement and identifies a continuum between poorly timed neg-ative reinforcement and punishment. It explores some of the problems of non-contingent punishmentand the prospect of learned helplessness and experimental neurosis. It concludes by introducing theconcept of ethical equitation.Crown Copyright � 2009 Elsevier Inc. All rights reserved.
Introduction
Training relies on timing and consistency and so, bydeduction, impaired learning soon arises when there isinconsistency and variable timing. Clear trainers are con-sistent in their signals and the way in which they set uppuzzles for an animal to solve (i.e., the way in which theypose questions). Good technique that reflects these qualitiesis more sustainable than the size or strength of handlers orindeed any devices that allow handlers to apply more force.
Punishment
Many events are aversive to horses. For example, a suddennoise, the sudden appearance of a stimulus, such as largeand/or moving objects, unfamiliar animals even including
int requests and correspondence: Paul D. McGreevy, Fac-
ry Science (B19), University of Sydney, Sydney, NSW
e front matter Crown Copyright � 2009 Elsevier Inc. All rig
eb.2008.08.001
their close relative, the donkey. Horse people typicallyclaim that the more unusual looking a species appears tothe horse (compared with those to which it has previouslybecome habituated) the more aversive it is. For example,the sight of ostriches and emus is particularly alarming tomost horses. Prey animals, such as horses, may evenbecome sensitized to aversive events and this can occurafter surprisingly few exposures (McGreevy and Boakes,2007). Consequently, experiments on fear conditioningcan be confounded by habituation. Furthermore, horsescan even become aroused and subsequently fearful as a re-sult of rider anticipation. When a rider is told to expect afear-eliciting stimulus to appear suddenly, his/her horse’sheart rate rises (Von Borstel et al., 2007).
Punishment refers to the presentation of a stimulus thatsuppresses a behavior (McGreevy et al., 2005). It can be di-vided into 2 categories: positive punishment and negativepunishment, depending on whether the punitive situationis either an added or removed stimulus (McGreevy,2007). Smacking, slapping, whipping, punching, and kick-ing are typical examples of positive punishment. However,
hts reserved.
194 Journal of Veterinary Behavior, Vol 4, No 5, September–October 2009
the term also embraces even minor amounts of discomfortthat suppress any behavior. Negative punishment is thewithholding of something attractive, such as food, that ispunitive by omission. It is usually not deliberately used inhorse training, but does, however, occur inadvertently. An-imals being trained in some new behavior will first attemptto offer an established response. The absence of reinforce-ment at that point makes repetition of this now-unwantedresponse less likely. Reinforcement has been omitted andtherefore the animal has been punished negatively. How-ever, defining punishment purely in terms of its suppressivefeatures is superficial. It is easy to imagine that at one timeor another in training, regardless of a trainer’s intention toreward or punish, some behavior is being thwarted at anygiven moment in favor of the one being carried out. Labelssuch as punishment are therefore limiting.
Punishment terminates the behavior that it follows. How-ever, the behavior that actually follows after the punisher isunimportant, whereas in negative reinforcement the behaviorthat ensues is critical. Thus the theoretic distinction betweenpunishment and negative reinforcement becomes tenuous ifthe behavior that follows punishment is consistent with a neg-atively reinforced goal. For example, if the punishing stimu-lus results in the same behavior each time, one could arguethat negative reinforcement is taking place. Take the exampleof trailer loading. In some countries, horse people have beenknown to use a long whip or stock whip on the animal’s hind-quarters when it refuses to go any farther. However, each timethe whip is used the horse runs backward faster, thus havingthe opposite effect to what was intended. What began as a fu-tile exercise in punishment has now turned into a (more fu-tile) process of negative reinforcement in which the horse,by running backward, has removed itself from the whip. Un-fortunately, the amount of violence meted out in the name ofpunishment is, all too often, totally out of proportion to theoriginal misdemeanor.
Punishment is associated with certain emotional statessuch as fear and frustration in the punished animal (Lindsay,2000) and has been shown to decrease learning in horses(Kratzer et al., 1977). Fear and anxiety can be adaptive inthat they raise vigilance and promote attempts to regain con-trol of aversive situations. Frustration enhances attempts atrestoring instrumental control over available reinforcers.Kandel et al. (2006) pointed out something that Freud also re-ported: that although certain amounts of fear and frustrationmay actually enhance learning, high levels tend to depress it,and may contribute to pathologic emotional states. Mills(1998) summarized an array of problems associated withpunishment. Specifically, punishment:
1. is nondirective, suppressing but not enhancing alterna-tive behaviors;
2. has the potential to desensitize an animal to the punish-ing stimulus if the punishment intensity is not optimal;
3. carries the risk of deleterious emotional changes that caninterfere with attention and learning; and
4. may be associated by the animal with the person deliv-ering it.
Mills (1998) concluded that punishment presents a rangeof problems that amount to abuse, and both are bestavoided. That said, it should be remembered that horsemanagement relies on punishment frequently. Consider anelectric fence, for example. The electric fence is not onlya positive punisher but also a highly aversive punisherthat may register as such a serious punitive event that an an-imal will scarcely venture to touch it a second time. As apunishing stimulus, an electric fence at least offers somecontrollability in the sense that the horse actively choosesto move away and release itself from the aversive stimulus.Compare this with an electric shock collar where the con-trols are in human hands. The animal has diminished con-trollability and is at the mercy of the skill and mood of ahuman. For this reason, many countries have outlawedthe use of electric shock collars.
Punishment is used commonly when a horse bites orkicks a human, lunges toward a human or threatens to doso. McLean (2005) has shown that biting and kicking cor-relate with specific dysfunctions of the go and stop signalsin-hand and under-saddle, so it follows that punishing thehorse for biting and kicking may be inadvisable. Further-more, it may not prevent future biting and kicking becauseit does not remove the cause. This important caution mustapply to all situations where punishment occurs. Punish-ment, therefore, may provide the wrong answer to a prob-lem and as a solution may be too simplistic.
An example is a show-jumping horse that is punished forhitting rails. It cannot be reformed by punishing it onlanding. In contrast, the importance of contingency hasprompted some jumping trainers to resort to anothertechnique: rapping. Rapping is an illegal practice (outlawedby the Federation Equestre Internationale rules) that in-volves an assistant hitting a horse’s forelegs as he clears ajumping obstacle. When this is done repeatedly there is atemporary alteration in perception of jumping effort re-quired for a given height.
Negative reinforcement versus positivereinforcement
Many animal trainers focus only on training via positivereinforcement, because their subjects are required to per-form at a distance and negative reinforcement (typically byapplying pressure) is not possible in these circumstances.Animals such as dolphins, seals, bears, zoo elephants, anddogs, to a large extent, are trained via positive reinforce-ment. In positive reinforcement, the trainer ignores errorsmade by the animal. If an animal takes fright, for whateverreason, during training, the trainer waits until the animalchooses to return to the training station. This presents noproblem when the subject is at liberty. However, when a
McGreevy and McLean Ethical Equitation 195
rider is astride the animal, the fleeing-animal situation iscritically dangerous. Horse, camel, and working elephanttrainers almost universally use negative reinforcementbecause by this means in adverse circumstances they canvirtually ‘force’ the animal to turn slow or go (Warren-Smith et al., 2007). Herein lies a fundamental differencebetween positive and negative reinforcement: in the latterthe trainer does not have to wait for the animal to offerthe response, he can orchestrate it.
Because of the damaging effects of its incorrect use,punishment should be used only when other avenues havebeen exhausted. In addition it is best used in conjunctionwith an antecedent secondary punisher (such as the word‘No!’) so that the primary punisher itself can be eliminatedat some stage. The need for caution with regard topunishment underscores the importance of teaching horseriding coaches the fundamentals of learning theory.
How to use negative reinforcement
Stimulus control can be defined as the degree to which thedesired response occurs in the presence of a specific stimulusand does not occur in the absence of this stimulus (McGreevyet al., 2005). In horse training, achieving stimulus control ofthe basic locomotory responses involves negative reinforce-ment (Warren-Smith et al., 2005, 2007; Warren-Smith andMcGreevy, 2007, 2008), and the following steps have beenproposed to achieve this (McLean, 2005):
1. The response to be trained is ‘targeted’ by the trainer. Itis important that only the targeted behavior results in theremoval of pressure/discomfort.
2. The pressure (aversive stimulus) should be increasedduring the ‘incorrect’ behavior. During this phase, thepressure must not fluctuate or decrease because this con-stitutes a lowering of pressure and thus could be per-ceived as reinforcing. The pressure is increased untilthe targeted response emerges.
3. If intermittent pressures are used (such as nudging bythe rider’s legs or tapping with a dressage whip) thereshould be no gaps greater than one second so that thehorse does not perceive this transient relief asreinforcing.
4. At the onset of the targeted response, the aversive stim-ulus should be removed immediately. Removal of theaversive stimulus must be absolutely contingent on theonset of the ‘correct’ behavior.
Non-contingent punishment
In cases where horse behavior is dangerous, such asbucking, rearing, shying, or bolting, trainers often feeljustified in delivering punishment. Sometimes this may beeffective, although it is difficult to conceive any practicalapproach for bolting. There are 2 common issues in this use
of punishment. (Both relate to the belief, in some circles,that the horse’s behavior was deliberate and that he is awareof his misdemeanors.) The first is the potential for exces-sive physical punishment (to ‘teach him a lesson’), whichhas no place in a modern training program, and the secondis the use of non-contingent punishment. For punishment tobe effective it must be contingent. Contingency means thepunishment must literally be connected to the offending be-havior. For example when punishing a horse for kicking,the punishment must occur while the horse is kicking orat the precise moment the kick ends. The use of non-contin-gent punishment is likely to confuse and frustrate for theanimals concerned and will most certainly have deleteriousconsequences, as it does with dogs (Lindsay, 2000).Because of such problems, punishment is best avoided.
Non-contingent punishment is ineffective
When jumping horses refuse obstacles, it is not uncommonfor trainers to use the whip as the horse stands motionless infront of the obstacle after its refusal. Punishment at thatpoint is non-contingent and therefore is devoid of anyuseful training effect. If it is going to be used, punishmentshould occur as the horse begins to slow or swerve. In somecases, the refusing horse is punished and then turned awayfor another presentation. When horses do attempt anobstacle after a random act of punishment, it is possiblethat increased anxiety levels enhance the flight responseand if the horse is successfully steered towards the obstacleit may well jump it. At best, this is a haphazard trainingexercise destined to have low efficiency, if any. At worst, itsimply trains the horse to default to a flight response in thepresence of jumps.
Learned helplessness
When animals are exposed repeatedly to pain in the form ofsustained, highly aversive stimuli, conditions such asexperimental neurosis may escalate so that the animalloses all active control. When the highly aversive stimulusis totally inescapable, learned helplessness may set in. Theimportant distinction here is that the animal no longer triesto cope; it gives up and becomes dull.
Learned helplessness was first identified by Seligmanand Maier (1967) and Maier et al. (1969) as a result of theirexperiments with dogs. These animals showed a deteriora-tion of cognitive, emotional and motivational attributes af-ter repeated exposure to inescapable aversive stimuli. In theexperiments, some dogs were trained to switch off an elec-tric shock, administered to their feet, by moving their headsideways, thereby contacting a switch. Other dogs weresimilarly shocked but were unable to switch off the elec-tricity. The next day, these 2 groups of dogs plus anotherunexposed group were subjected to electric shocks in a
196 Journal of Veterinary Behavior, Vol 4, No 5, September–October 2009
shuttle box apparatus, where the shocks could be termi-nated by the dogs jumping a small hurdle. All dogs rapidlylearned to jump the hurdles except some of the group thathad been unable to avoid the shocks during the experimentthe previous day. Those dogs were helpless and instead oftrying a response to avoid the shocks, they showed intensehyper-reactivity and then became passive. Weinraub andSchulman (1980) proposed more recently that it was theuncontrollability of the experience rather than the experi-ence of shock itself that interfered with subsequent avoid-ance learning. It was noted that with sufficient exposures,diminished aggression, and a loss of appetite occurredand the apathy of these dogs persisted long after the exper-iment. Some trainers may argue that learned helplessnessmodels of horse training (that may include burying horsein grain or even casting) are ethically justified in cases ofaggression. The current authors do not concur, becausemost cases of aggression are based in fear, play, and re-source guarding and so can be resolved by removing themotivating causes.
Investigating the effects of previous exposure and con-trollable shock with rats, Seligman (1975) showed that pastexperience in dealing with escapable shock immunized sub-jects from the effects of learned helplessness when exposedto inescapable shock later on. On the other hand, naıve ratsthat had never been exposed to escapable shock becamehelpless after exposure to inescapable shock. Furthermore,Hannum et al. (1976) showed that rats with previous expe-rience in escaping shock early in their lives performed bet-ter in escape learning tasks than did nonshocked controls.In dogs it has been shown that individuals exposed repeat-edly to excessive punishment, where they have learned totolerate pain but not to benefit from it, gradually becomeunmoved by increasing pain (Lindsay, 2000). Previous ex-posure to correct pressure-release can partially immunizehorses against subsequent bad riding but bad breaking-incan leave a lifetime legacy.
The symptoms of learned helplessness in rats and dogsthat have been noted include anhedonia, depression, moti-vational, emotional, and cognitive deficits (Seligman andAltenor, 1980). Worse still, in the experiments carried outby Weiss et al. (1975) as well as Seligman and Maier(1967), several rats and dogs died as a direct result of theexperimental treatments. These events confirm the impor-tance to animals of predictability and controllability, partic-ularly when they are dealing with aversive stimuli. It is notsurprising that learned helplessness has been held as an an-imal model of human reactive depression and post-trau-matic stress syndrome (Hall et al., 2007). The neuraltissues responsible for generating experimental neurosisand learned helplessness are similar to those that generatedepression in humans (Cabib, 2006) and their mechanismsseem to share a profound inhibition of dopamine release inthe nucleus accumbens.
Learned helplessness in horses remains unresearchedand subject to considerable speculation at this stage.
However, several researchers have identified the possibility(Odberg, 1987; Lieberman, 1993; Odberg and Bouissou,1999). It is likely that some behavioral responses exhibitedby the domestic horse are indeed examples of learned help-lessness. McLean and McGreevy (2004) pointed out that al-though many horse people assume the loss of sensitivity inhorses with ‘hard mouths’ and ‘dead sides’ is the result ofaccumulated scar tissue, it is more likely to reflect habitu-ation. Just where this habituation emerges on the continuumthat terminates in learned helplessness is not clear. How-ever, the practice of using contradictory acceleration anddeceleration signals simultaneously and indeed deliveringthese signals via amplifiers such as the (lever-action)curb-bit and rowelled spurs make the horse a likely candi-date for learned helplessness. Learned helplessness wouldshow up only after the failure of active coping mechanismssuch as bucking and hyper-reactivity. Established learnedhelplessness may compromise horse welfare because an an-imal in this state has undergone a critical loss of control ofits environment (Webster, 1994).
Experimental neurosis
We have seen that gaining control over aversive stimuli isof vital importance to animals. When such control isthwarted, the animal’s well-being is threatened and neuro-sis may develop. Hence, extra care must be taken whentraining animals using aversive stimuli because of animals’imperative to achieve control over such stimuli. Solomon(1964) showed that maladaptive behavior arises when:
1. there are sustained raised levels of arousal;2. the aversive stimulus is unpredictable;3. the aversive stimulus is uncontrollable; and4. the aversive stimulus is inescapable.
Numerous studies attest the problems that emerge whenthese conditions arise. Pavlov’s (1941) experiments withdogs provided one of the earliest accounts of experimentalneurosis, based on discrimination training. In one experi-ment, he rewarded dogs for associating a leg movementwith a circular patch of light, but punished them with anelectric shock when they responded to an elliptical one.When the dogs had learned these associations, he begansome alterations to the experiment: the elliptical patchwas made more circular. At some point the dogs were un-able to distinguish between a rewarded shape and a pun-ished one. Some of the dogs became very aggressivewhereas others gave up responding and fell asleep. Masser-man (1950) carried out a similarly confounding experimenton cats. He trained cats to open a box for a food rewardwhen signaled by a light. Later, when the food box wasopened, the cats sometimes received an aversive outcome,such as a blast of air. Again, some of the cats became ex-citable and hyper-reactive whereas others became dulland refused to move.
McGreevy and McLean Ethical Equitation 197
Because of their reliance on stimuli that have their basisin aversiveness, horse trainers should be very careful toensure that the cues and pressures they use result inconsistent learned responses and that these operant contin-gencies do not change throughout the animal’s life. Theprevalence of hyper-reactivity and dullness among trainedhorses suggests that at least some training methodologiespay scant regard to the maintenance of consistent operantcontingencies throughout the horse’s life. For example, insome dressage training systems, self-carriage (that impliesthe absence of aversive pressure) is seen as a phenomenonthat may take years to develop. This suggests that theimportance of the reinforcement component of negativereinforcement is either ignored or not understood.
In conclusion, the current knowledge base on the correctuse of punishment in equitation is limited. Any attempts toremedy this deficiency should focus on the use of subtlepunishers that minimize the need to escalate force. Thisapproach would contribute to the development of ethicalequitation.
Ethical equitation
The issue of ethical equitation is fascinating and largelyunexplored. The extent to which sport horses are coerced toperform is often the focus of welfare debates. Coercionsmacks of slavery and is regarded as distasteful by manyanimal lovers but, given that negative reinforcement is thecritical mechanism, horses cannot be safely ridden withoutsome degree of pressure. Ethical equitation demands thatminimal pressure is used for both contact (depending on thesport) and signaling at all times.
References
Cabib, S., 2006. The Neurobiology of Stereotypy II: the Role of Stress. In:
Mason, G., Rushen, J. (Eds.), Stereotypic Animal Behaviour: Funda-
mentals and Applications to Welfare, 2nd Ed.. CABI, Oxon, UK,
pp. 227-255.
Hall, C., Goodwin, D., Heleski, C., Randle, H., Waran, N., 2007. Is there
evidence of learned helplessness in horses? In: Goodwin, D.,
Heleski, C., McGreevy, P., McLean, A., Randle, H., Skelly, C., van
Dierendonck, M., Waran, N. (Eds.), Proceedings of the 3rd Interna-
tional Equitation Science Symposium. Michigan State University,
East Lansing, Michigan; August 13-14, 2007;8.
Hannum, R.D., Rosellini, R.A., Seligman, M.E.P., 1976. Learned helpless-
ness in the rat: Retention and immunization. Dev. Psychobiol. 12,
449-454.
Kandel, E.R., Schwartz, J.H., Jessell, T.M., 2000. Principles of Neural Sci-
ence, 4th Ed. McGraw-Hill, NY.
Kratzer, D.D., Netherland, W.M., Pulse, R.E., Baker, J.P., 1977. Maze
learning in quarter horses. J. Anim. Sci. 45, 896-902.
Lieberman, D.A., 1993. Learning: Behaviour and Cognition. Brooks/Cole
Publishing, Pacific Grove, CA, pp. 528.
Lindsay, S.R., 2000. Adaptation and learning. In: Handbook of Applied
Dog Behaviour and Training., Vol. 1. Iowa State University Press,
Ames, IA, pp. 298-305.
Maier, S.F., Seligman, M.E.P., Solomon, R.L., 1969. Pavlovian fear condi-
tioning and learned helplessness: Effects on escape and avoidance
behavior (a) the CS-US contingency and (b) the independence of the
US and voluntary responding. In: Campbell, B., Church, R.M. (Eds.),
Punishment and Aversive Behaviour. Holt. Rinehart and Winston, NY
Masserman, J.H., 1950. Experimental neurosis. Sci. Am. 182, 38-43.
McGreevy, P.D., 2007. The advent of equitation science. Vet J. 174,
492-500.
McGreevy, P.D., Boakes, R.A., 2007. Carrots and Sticks: Principles of An-
imal Training. Cambridge University Press, Cambridge, UK, pp. 2-23.
McGreevy, P.D., McLean, A.N., Warren-Smith, A.K., Waran, N., Good-
win, D., 2005. Defining the terms and processes associated with equi-
tation. In: McGreevy, P., McLean, A., Waran, N., Goodwin, D.,
Warren-Smith, A. (Eds.) Proceedings of the 1st International Equita-
tion Science Symposium, Broadford, Victoria, Post-Graduate Founda-
tion in Veterinary Science, Sydney; August 26-27, 2005; pp. 10-43.
McLean, A.N., 2005. The mental processes of the horse and their conse-
quences for training. PhD thesis, University of Melbourne.
McLean, A.N., McGreevy, P.D., 2004. Training. In: McGreevy, P.D. (Ed.),
Equine BehaviourdA Guide for Veterinarians and Equine Scientists.
W.B. Saunders, Edinburgh, UK, pp. 291-311.
Mills, D.S., 1998. Applying learning theory to the management of the
horse: The difference between getting it right and getting it wrong.
Equine Vet. J. Suppl. 27, 10-13.
Odberg, F.O., 1987. Chronic stress in riding horses. Equine Vet. J. Suppl.
18, 268-269.
Odberg, F.O., Bouissou, M.-F., 1999. The development of equestrianism
from the baroque period to the present day and its consequences for
the welfare of horses. The role of the horse in Europe. Equine Vet.
J. Suppl. 28, 26-30.
Pavlov, I.P., 1941. Lectures on Conditioned Reflexes. International Pub-
lishers, NY.
Seligman, M.E.P., 1975. Helplessness: On Depression. In: . Development
and Death. W.H. Freeman and Company, San Francisco, CA.
Seligman, M.E.P., Altenor, A., 1980. Coping behavior: Learned helpless-
ness, physiological change, and learned inactivity. (Seligman-Weiss
Debate). Behav. Res. Ther. 18, 459-512.
Seligman, M.E.P., Maier, S.F., 1967. Failure to escape traumatic shock.
J. Exp. Psychol. 74, 1-9.
Solomon, R.L., 1964. Punishment. Am. Psychol. 19, 239-253.
Von Borstel, U.U., Duncan, I.J.H., Shoveller, A.K., Millman, S.T.,
Keeling, L.J., 2007. Transfer of nervousness from competition rider to
the horse. In: Goodwin, D., Heleski, C., McGreevy, P., McLean, A.,
Randle, H., Skelly, C., van Dierendonck, M., Waran, N. (Eds.), Proceed-
ings of the 3rd International Equitation Science Symposium. Michigan
State University, East Lansing, Michigan; August 13-14, 2007;17.
Warren-Smith, A.K., Curtis, R.A., Greetham, L., McGreevy, P.D., 2007.
Rein contact between horse and handler during specific equitation
movements. Appl. Anim. Behav. Sci. 108, 157-169.
Warren-Smith, A.K., McLean, A.N., Nicol, H.I., McGreevy, P.D., 2005.
Variations in the timing of reinforcement as a training technique for
foals. Anthrozoos. 18 (3), 255-272.
Warren-Smith, A.K., McGreevy, P.D., 2007. The use of blended positive
and negative reinforcement in shaping the halt response of horses
(Equus caballus). Anim. Welf. 16, 481-488.
Warren-Smith, A.K., McGreevy, P.D., 2008. Equestrian coaches’ under-
standing and application of learning theory in horse training. Anthro-
zoos. 21, 153-162.
Warren-Smith, A.K., McLean, A.N., Nicol, H.I., McGreevy, P.D., 2005.
Variations in the timing of reinforcement as a training technique for
foals. Anthrozoos. 18, 255-272.
Webster, A.J.F., 1994. Animal welfare: A cool eye towards Eden. Black-
well Science, London, UK.
Weinraub, M., Schulman, A., 1980. Coping behavior: Learned helpless-
ness, physiological change and learned inactivity. Behav. Res. Ther.
18, 459-512.
Weiss, J.M., Glazer, H.I., Pohorecky, L.A., Brick, J., Miller, N.E., 1975.
Effects of chronic exposure to stressors on avoidance-escape behavior
and on brain norepinephrine. Psychosom. Med. 37, 522-533.