FAILURE TO FIND REINFORCEMENT EFFECT OF NECK PATTING IN HORSES (EQUUS CABALLUS)

Transcription

1 Psychologia, 2016, 59, FAILURE TO FIND REINFORCEMENT EFFECT OF NECK PATTING IN HORSES (EQUUS CABALLUS) Akio TAKAHASHI 1), Keita NISHIYAMA 2), Midori OHKITA 1), and Kosuke SAWA 1) 1) Department of Psychology, Senshu University, Japan 2) Graduate School of Science & Engineering, Teikyo University of Science, Japan From the perspective of animal welfare, positive reinforcement should be used in animal training situations, such as an equestrian event. To assess the reinforcement properties of patting the neck of horses, a simple instrumental conditioning test was administered. Three horses were required to press a button with their nose for a food pellet and patting. ABA reversal design was administered to assess the relative reinforcement properties of patting to food reinforcement; and, the reinforcement schedule for the food reinforcer was gradually changed from the continuous reinforcement (CRF) to a fixed ratio (FR) 5. All subjects consistently showed a low level of response for a patting reinforcer, suggesting that reinforcement effect of neck patting may be trivial, if any. KKey words: instrumental conditioning, positive reinforcement, neck patting, horses Introduction Horses (Equus caballus) were domesticated about 3500 B.C., and they have been closely associated with human beings for about 5500 years (Outram et al., 2009). Horses have a multiplicity of abilities, with the most important aspect being driving power. Because of the text, Art of Horsemanship and the Cavalry Commander, written by Xenophon in ancient Greece, we understand that the most important factor of the horse was driving power, for complete control in armed combat. The technique to control the horse, Equestrian, was adapted and improved in line with various traits of the horses and the purposes of use. Since humans use horses for various purposes, it is important to introduce adequate methods of training. It is well known that classical conditioning and instrumental conditioning are effective to train horses (e.g., McGreevy, 2007; McCall, 1990), as well as other mammals, including humans. Instrumental conditioning is especially important in horse training because it allows us to modify complex voluntary behavior of organisms, which is required in horsemanship such as dressage. In the instrumental conditioning procedure, developed by Thorndike and elaborated by Skinner and behavior analysts, This research was supported by JSPS Grant-in-Aid for Scientific Research on Innovative Areas Grant Number JP Correspondence concerning this article should be addressed to Kosuke Sawa, Department of Psychology, Faculty of Human Sciences, Senshu University, 1-4-5, Higashimita, Tama-Ku, Kawasaki, Kanagawa , Japan ( sawa@psy.senshu-u.ac.jp). 91

2 92 TAKAHASHI, NISHIYAMA, OHKITA, & SAWA organisms learn the relationship between their own behavior and environment, to change their behavior. To achieve a better performance in the horsemanship competition, increasing appropriate (and reducing inappropriate) behavior to match the criteria for scoring is crucial. Developing an adequate method of instrumental conditioning in horses, therefore, has gathered broad attention. The three-term contingency, a fundamental unit for analyzing instrumental behavior, consists of a discriminative stimulus, a response, and an outcome (i.e., reinforcement). Because the target behavior is fixed in the setting of horsemanship, the targets of intervention are discriminative stimuli and outcomes. In horsemanship, people use various discriminative stimuli (signals), such as weight shift, pressure to the horse s belly, rein movements, voices, and whip movements to signal instructions to the horse. Handlers and riders have horses carry out appropriate and complex movements by combining and arranging the strengths of these methods. Many studies concerning information transmission from humans to horses used human movements and gaze as clues. For example, Maros, Gácsi, and Miklósi (2008) reported that horses could use the information from human pointing in an object selection task, if the human experimenter continuously presented a pointing signal until the horse made a decision. Proops and McComb (2010) also suggested that horses might use continuous pointing and physical cues for object selection, although instantaneous tapping and a combination of human gaze and head-direction were not effective for object selection. These studies focused on the role of visual information such as human gestures (e.g., pointing). But, in signal transmission from humans to horses in actual horsemanship, combination of multiple modalities (e.g., voice signal and physical contact) has been used. The International Society for Equitation Science (ISES) formulated the first principles for horse training, based on ethological research of learning and cognitive ability in horses. This formulation, in which ten different methods of training are discussed, recommends use of salient signals that are easy to discriminate for horses (McGreevy & McLean, 2007). Various studies have reported outcome of behavioral selection using instrumental conditioning. Traditionally, negative reinforcement procedures have been used to shape horse behavior (McGreevy, 2007; McCall, 1990). In a negative reinforcement procedure, a response is more likely in the future to occur if it brings about the removal of an aversive stimulus. Aversive pressure of a bit through the reins could disappear if the horse shows required behavior. Riders give the pressure through their legs and spurs and then remove the pressure when the horse starts to move. These situations are common in horse training, and are simple examples of negative reinforcement. However, these negative reinforcement procedures may possibly cause a severe byproduct such as learned helplessness, if the trainer fails to control the timing of the introduction and removal of the aversive stimulus (McGreevy & McLean, 2009). This point raises the important role of positive reinforcement in horse training instead. Effects of positive reinforcement in horse training have been investigated in experimental situations. For example, Miyashita, Nakajima, and Imada (2000) explored visual discrimination in horses using food pellets and carrots as reinforcement, and reported that a differential outcome procedure enhanced discrimination performance. This result suggests that positive reinforcement is useful, and that horses could use information

3 LACK OF PATTING REINFORCEMENT EFFECT IN HORSES 93 from the quality of the reinforcement for visual discrimination. The effect of positive reinforcement also contributes to horses wellbeing. Innes and McBride (2008) used positive reinforcement training for rescued equids that had been under neglect or cruelty, and reported that positive reinforcement, with the use of a clicker as secondary reinforcement, facilitated exploratory or trial and error type behaviors in novel situations, compared to negative reinforcement training. Although positive reinforcement has various advantages in horse training, some difficulties may be pointed out. If a horse receives too much primary reinforcement such as food, this may affect the health condition. At times, satiation for primary reinforcement may reduce the effect of the reinforcement itself. Furthermore, use of food reinforcement is difficult while horse riding. In the present study, we focused on neck patting. Although some researchers have pointed out that neck patting has no reinforcement properties, and that pairing it with primary reinforcement to achieve secondary reinforcement power is required instead (McGreevy, 2004; McLean, 2003), neck patting has traditionally been used as a technique to reward or soothe horses (German National Equestrian Federation, 2013; Podhajsky, 1967). Still, empirical evidence for the lack of reinforcement properties does not seem to be sufficient. The main purpose of the present study is to identify the reinforcing power of neck patting by using an ABA reversal design. The horses first received instrumental training with small food pellets as reinforcement (Condition A). Then, the reinforcer was switched to neck patting (Condition B) to explore how strongly it would maintain the learned instrumental response. Method Subjects The subjects used were 3 gelding (castrated male) horses: a 6-year-old Thoroughbred, 11-year-old Mix breed, and a 12-year-old Thoroughbred from the Tokyo University of Agriculture and Technology equestrian stable. Horses that were low in aggression toward humans were selected to eliminate risk. The experiment was performed in an empty stall of same conditions that the horses were living in. Setting Horses were guided to an individual stall with a handmade wooden operant panel (40 cm 30 cm; Fig. 1). A response button (10 cm 10 cm) painted with black and white vertical lines (1.6 cm for each line) was located at 10 cm from the top, and 10 cm from the side of the operant panel. A food pellet as a reinforcer (Yushun; Nosan Corporation, Yokohama, Japan) was manually delivered by an experimenter who stood behind the operant panel to a steel bowl located 10 cm below the response button from the other side of the operant panel. A response to the button was detected with a micro switch, which was connected to the buzzer; the buzzer sounded while the button was pressed. The operant panel was located at the window of the narrow side of the stall. Procedure All experimental procedures were conducted within individual stalls. Horses received one training or experimental session a day. The interval of sessions was basically a day, but sometimes several days for various reasons (for example, horses had to move to competition). Training and experimental procedures had lasted about three months. Prior to the experimental session, all subjects received a habituation period to the experimental panel, and a magazine training session, in which the presenting buzzer sound was paired with the delivery of a food pellet. In the magazine training session, the food pellet and buzzer sound were presented

4 94 TAKAHASHI, NISHIYAMA, OHKITA, & SAWA Fig. 1. Experiment setup. a) Actual image of the operant panel. b) Schematic of the operant panel. every 10 sec for 5 min. Then, subjects received shaping training, in which they pressed the button with their nose, with groom in the individual stall. All button-pressing responses were reinforced with a food pellet and buzzer sound. A molding procedure was used if necessary. In the case that subjects did not face the experimental panel, the groom guided their heads to the panel to allow them to press the button. After five sessions of shaping training, the groom left the subject alone, and confirmed the stable level of response for three sessions. Each training session lasted no longer than 10 min. After finishing the shaping, the experimental session was introduced. All experimental sessions lasted 10 min. In the first phase of the experimental sessions, the continuous reinforcement (CRF) schedule was administered to all subjects, and all button-pressing was reinforced with food and a buzzer sound. The groom stood by the subjects without making any physical or eye contact with them. After confirming a stable level of response, the reinforcer was replaced with physical patting on the neck and a buzzer sound. The grooms were instructed to pat the horse s neck two times with strength of daily uses. Based on the ABA reversal design, the reinforcer was replaced again with a food pellet and the buzzer sound after confirming a stable level of response (CRF Block). Following the first reversal, the reinforcement schedule with the food pellet was changed to a fixed ratio (FR) of 2, 3, 4, and 5, in order to assess the reinforcement property of patting (CRF + FR Block). The main aim of the change of the reinforcement schedule of food was to reduce the relative value of food reinforcement for each response, and to emphasize the reinforcement property of patting. Because of the unstable response level, one of the three subjects received the CRF schedule with a food pellet only. Results Fig. 2 depicts the number of button-presses across sessions for three subjects. In the first CRF phase, all subjects showed a stable level of response. In Horse 3, the data on session 29 was missing because of malfunction of the apparatus. The number of buttonpresses were dramatically decreased in the phase in which patting was used as reinforcement for all subjects. Then, the response level recovered again after the introduction of the food reinforcement. Two subjects received food reinforcement, and FR 2 and 3 induced an increased level of response; but, low rates of response were seen in the phase in which patting was used as reinforcement; and, the same trends were seen in the FR 4 and 5

5 LACK OF PATTING REINFORCEMENT EFFECT IN HORSES 95 Fig. 2. The number of button presses across sessions for three subjects.

6 96 TAKAHASHI, NISHIYAMA, OHKITA, & SAWA phases. Even when the FR 5 schedule was introduced, in which they had to respond five times to earn the single food pellet, the response magnitude of the subjects in the patting phase immediately after FR 5 schedule apparently decreased. These results clearly suggest that physical patting had very little reinforcement properties, at least in the present settings. In order to identify the difference between the number of button-presses in the food phases and in the patting phases for each subject, single-case randomization tests (Twotailed tests) were conducted (R-package; SCRT; Bulté & Onghena, 2008). An alpha level of.05 was used. In CRF Blocks, there were significant differences in all subjects (Horse1: p =.040, Horse2: p =.003, and Horse3: p =.002). Next, In CRF + FR Blocks, as well as in CRF Blocks, there were significant differences in both subjects 1 (Horse1: p =.027, and Horse2: p <.001). Discussion Positive reinforcement is important in animal training, not only from the perspective of animal welfare, but also of safety for trainers and people around the animals. Physical patting seemed to be a convenient way of giving positive reinforcement to horses, but the present results suggested that it was not sufficient even to maintain simple instrumental responses, such as button-pressing. These results are consistent with those of a questionnaire for equestrian coaches, in which less than 10% of participants reported that neck patting was an effective reward (Warren-Smith & McGreevy, 2008). Unlike the broad purpose and intentions behind this common equestrian practice, empirical results implied that neck patting might have little effect on horse behavior. The present experiment adopted an ABA reversal design in order to detect the relative reinforcement efficacy of neck patting, compared with a small food reward. In applied behavior analysis, behavioral pharmacology, and behavioral economics, progressive ratio schedules have been used to measure the reinforcement value of a stimulus or an event (Hodos, 1961; Hodos & Kalman, 1963; Rowlett, 2000; Stafford, LeSage, & Glowa, 1998; Stoops, 2008). In a progressive ratio schedule, the number of instrumental responses required to obtain reinforcement gradually increases. For example, in the initial phase of training, every target response is followed by reinforcement. Two responses are required for reinforcement in next block, and four responses are required in the block afterwards, etc. By increasing the number of required responses, the organism would give up on performing the instrumental response at some point (break point) and the break point may be an index of reinforcement efficacy. Although it is technically possible to employ a progressive ratio schedule to detect the reward value of neck patting in horses, as seen in present results, horses may not maintain instrumental responses across the increasing criterion to obtain reinforcement, such as neck patting. In the present study, neck patting was introduced as reinforcement to maintain instrumental responses originally supported by food reinforcement. Generally speaking, 1 Because the responses of Horse3 were the unstable in CRF Block, Horse3 did not receive CRF + FR Block.

7 LACK OF PATTING REINFORCEMENT EFFECT IN HORSES 97 the reward value of food appeared strong; thus, there is a possibility that the negative contrast effect from food to neck patting reduced the true efficacy of neck patting. However, the food pellet used in the present research was about 5 g, which was trivial relative to the daily diet of horses, and neck patting failed to maintain a simple instrumental response, even when the reinforcement schedule with food was changed from CRF to FR5. One may introduce neck patting as reinforcement in the initial training. But, from the perspective of an equine training situation, the application of neck patting as a reinforcer may not be interesting or useful because of its very small efficacy. Another possible reason of failure to find the reinforcement efficacy of neck patting is that neck patting might be a signal of no food in daily life of horses. If people around the horse routinely use neck patting without food or other effective rewards, neck patting could be a signal of lack of rewards. But it seems difficult to control this possibility in the present setting. Further research is needed. Then, does neck patting have no significance to horses? Thorbergson, Nielsen, Beaulieu, and Doyle (2016) explored whether neck patting and wither scratching have any effects on changing heart rate and other various horse behaviors related with relaxation. They reported that wither scratching may produce behavior related to relaxation for significantly longer than neck patting and the control procedure. This result also implied that wither scratching might have had a weak effect on horse relaxation and the reinforcement of instrumental behavior. This is because, when scratching, the human hand tends to maintain touch on the horse s surface for a longer duration than patting. These factors might contribute the difference in efficacy and patting with longer duration might have some effect. Feuerbacher and Wynne (2012) investigated the relative reward efficacy of social interaction (scratching the animal around the neck with both hands while praising it verbally) between humans, dogs, and wolves, by comparing social interaction and food reward. Dogs have been involved in human society for a long time, as well as horses. Feuerbacher and Wynne (2012) hypothesized that human social interaction may have more reward value for dogs (McIntire & Colley, 1967) than wolves. But results did not support this hypothesis, because the social interaction showed a weak reward efficacy relative to the food reward both in dogs and wolves. These results were consistent with the present result, but in different species. Feuerbacher and Wynne (2012) discussed the possibility that only social interaction from conspecifics could have reward efficacy, in reference to the horse example (Søndergaard, Jensen, & Nicol, 2011), and Feh and de Mazieres (1993) also suggested that wither grooming from conspecifics reduced heart rate in horses. Relatedly, Feuerbacher and Wynne (2014) revealed that relationship of those who provided the social scratching (owner of the dog or stranger) had some effect on the efficacy of social reinforcement. These findings seem to imply that the familiarity of the agent providing social interaction is important for its efficacy. Additionally, it is possible that social interaction has multiple roles in terms of reward, such as relaxation or reinforcement of response. Thorbergson et al. (2016) showed that wither scratching by a human also reduced heart rate in horses, suggesting that human scratching may relax horses, but may not reinforce an instrumental response. Although it is still unclear which factor is the most

8 98 TAKAHASHI, NISHIYAMA, OHKITA, & SAWA critical, according to the horse training literature, it may be fruitful to choose a body part that is easy to touch and interact with. As discussed, neck patting is social interaction between a human and a horse. It is possible that social relationship between them could play some role for reinforcing efficacy of neck patting. In the present experiment, the social relationship between the groom and the horse was not controlled so this possibility could not be ruled out. Additionally, it might be possible that neck patting as social interaction could have some reinforcement property in specific social situation but not in the present experimental settings. Focused on the characteristics of social meaning, further explanation might reveal the detail of the role of neck patting. In the present study, we could not obtain evidence to recommend the use of neck patting in horse training. However, it may still be important to find candidates for a positive reward stimulus and procedure, one that is easy to use in horse training methods that use positive reinforcement in equine settings. As Warren-Smith and McGreevy (2008) reported, only 3% of equine coaches who participated in their research could explain what positive reinforcement was, even though 80% of them answered that positive reinforcement is useful. A similar misunderstanding was seen also in punishment, in which only 5% could explain the meaning of punishment. The present finding might provide a small piece of the puzzle for improving training efficacy and the welfare of horses. REFERENCES Bulté, I., & Onghena, P An R package for single-case randomization tests. Behavior Research Methods, 40, Feh, C., & de Mazieres, J Grooming at a preferred site reduces heart rate in horses. Animal Behaviour, 46, Feuerbacher, E. N., & Wynne, C. D Relative efficacy of human social interaction and food as reinforcers for domestic dogs and hand-reared wolves. Journal of the Experimental Analysis of Behavior, 98, Feuerbacher, E. N., & Wynne, C. D Most domestic dogs (Canis lupus familiaris) prefer food to petting: Population, context, and schedule effects in concurrent choice. Journal of the Experimental Analysis of Behavior, 101, German National Equestrian Federation The principles of riding. Shrewsbury, United Kingdom: Kenilworth Press. Hodos, W Progressive ratio as a measure of reward strength. Science, 134, Hodos, W., & Kalman, G Effects of increment size and reinforcer volume on progressive ratio performance. Journal of the Experimental Analysis of Behavior, 6, Innes, L., & McBride, S Negative versus positive reinforcement: An evaluation of training strategies for rehabilitated horses. Applied Animal Behaviour Science, 112, Maros, K., Gácsi, M., & Miklósi, Á Comprehension of human pointing gestures in horses (Equus caballus). Animal Cognition, 11, McCall, C. A A review of learning behavior in horse and its application in horse training. Journal of Animal Science, 68, McGreevy, P. D Equine behavior: A guide for veterinarians and equine scientists. London, United Kingdom : Saunders. McGreevy, P. D The advent of equitation science. The Veterinary Journal, 174, McGreevy, P. D., & McLean, A. N Roles of learning theory and ethology in equitation. Journal of Veterinary Behavior: Clinical Applications and Research, 2,

9 LACK OF PATTING REINFORCEMENT EFFECT IN HORSES 99 McGreevy, P. D., & McLean, A. N Punishment in horse-training and the concept of ethical equitation. Journal of Veterinary Behavior: Clinical Applications and Research, 4, McIntire, R., & Colley, T. A Social reinforcement in the dog. Psychological Reports, 20, McLean, A. N The truth about horses. Victoria, Australia: Australian Equine Behaviour Centre. Miyashita, Y., Nakajima, S., & Imada, H Differential outcome effect in the horse. Journal of the Experimental Analysis of Behavior, 74, Outram, A. K., Stear, N. A., Bendrey, R., Olsen, S., Kasparov, A., Zaibert, V.,... Evershed, R. P The earliest horse harnessing and milking. Science, 323, Podhajsky, A The complete training of horse and rider in the principles of classical horsemanship. Woodland Hills, CA: Wilshire Book. Proops, L., & McComb, K Attributing attention: The use of human-given cues by domestic horses (Equus caballus). Animal Cognition, 13, Rowlett, J. K A labor-supply analysis of cocaine self-administration under progressive-ratio schedules: Antecedents, methodologies, and perspectives. Psychopharmacology, 153, Søndergaard, E., Jensen, M. B., & Nicol, C. J Motivation for social contact in horses measured by operant conditioning. Applied Animal Behaviour Science, 132, Stafford, D., LeSage, M. G., & Glowa, J. R Progressive-ratio schedules of drug delivery in the analysis of drug self-administration: A review. Psychopharmacology, 139, Stoops, W. W Reinforcing effects of stimulants in humans: Sensitivity of progressive-ratio schedules. Experimental and Clinical Psychopharmacology, 16, Thorbergson, Z. W., Nielsen, S. G., Beaulieu, R. J., & Doyle, R. E Physiological and behavioral responses of horses to wither scratching and patting the neck when under saddle. Journal of Applied Animal Welfare Science, 19, Warren-Smith, A. K., & McGreevy, P. D Equestrian coaches understanding and application of learning theory in horse training. Anthrozoös, 21, (Manuscript received 31 August, 2016; Revision accepted 24 October, 2016)