Pavlovian to Instrumental Transfer: A Study Done On Horses

A study was done on 19 Anglo-Arabian horses who were exposed to identical conditions at the experimental station of the French National Stud. 

Each of these horses was made to go through three principal stages. These included Pavlovian Conditioning (also known as classical conditioning), instrumental conditioning (also known as operant conditioning), and Pavlovian to Instrumental Transfer (PIT) test. 

All the 19 horses were made to experience these stages for five weeks. Also, temperamental tests were conducted on all the horses towards the end of the experiment. 

Over the five-week period, the animals were maintained together on a pasture. Further, the horses were enclosed separately inside 6m x 3m loose boxes with adjoining 3m x 3m outside area for four hours. This was done five days a week. 

Thus, animals were enclosed in these conditions for a five-week period and were housed on bedding made out of wood shavings. Also, there was a feed bucket that was put on the front door of every box. Likewise, water and hay were provided as necessary in the pasture as well as the outside area. And no limitation was exercised on food. 

The idea was to study PIT in hoofed animals and to see if the efficiency of PIT can be regulated by the individual temperament of each of the horses. 

Let’s have a look at how the three stages of Pavlovian conditioning, instrumental conditioning, and PIT were used to understand the relationship between the effectiveness of PIT and certain temperamental dimensions. 

The Design of the Experiment

As specified earlier, the horses were made to go through three stages. These included Pavlovian Conditioning, instrumental conditioning, and a PIT test. Each of the 19 horses was subjected to these three stages for a period of five weeks. 

In addition to this, each of them was also subjected to temperamental tests towards the end of the experiment. 

The Experimental Conditions

All the 19 horses, including 13 males and 6 females, were reared in the following under identical conditions: 

• Until the age of 6±1 months - maintained on the pasture with their dam and were weaned

• From weaning until the age of 11 months - enclosed indoors. The males were castrated at the age of 10 months. 

• 11 months of age onwards - horses lived on the pasture till the beginning of the experiment. 

Stage I: Pavlovian Conditioning

Pavlovian Conditioning is a technique of learning in which a neutral stimulus is associated with a natural stimulus that has the potential to trigger a natural response.  

Eventually, the neutral stimulus repeatedly occurring with the natural stimulus becomes capable of eliciting the natural response, even in the absence of the natural stimulus. 

Pavlovian Conditioning Stage in the Experiment

In this experiment, the horses were made to associate an auditory-visual stimulus, a Conditioned Stimulus (CS) in this case, with the food delivery into the feed bucket. 

Each of the horses could roam about freely into the box. Whereas the experimenter stood 2m  in front of the box. Accordingly, the CS involved the experimenter shaking a 1-liter plastic jug that contained 500 grams of pellets. These CS presentations continued for 2 minutes and 8 such CS presentations were done during 32-minute sessions. The experimenters conducted 9 32 minute sessions, one daily for the first 5 days and one weekly for the following 4 weeks. 

Also, the 8 CS presentations in each session were scattered with periods or intertrial intervals (ITI) in which each of the horses was not subject to any stimulus. These ITIs ranged from 1.5 to 3 minutes. 

Further, during the 2 minute CS presentations, the experimenter dispensed a small number of pellets four times into the feed bucket. This was done at various intervals, called intertrial intervals (ITIs). The duration of these intervals varied from 2 seconds, 30 seconds, 1 min, and 1.5 min post the beginning of the CS. 

Thus, the experimenters made a number of observations during the Pavlovian Conditioning stage. For instance, horses not eating pellets were removed after 20 seconds. Likewise, for every session and distribution, horses that ate pellets in less than 20 seconds were recorded. 

Also, their behaviors towards the feed bucket including licking, biting, etc were observed. 

Stage II: Instrumental Conditioning

Instrumental conditioning is a learning technique according to which change in behavior depends on the outcome of an event. Thus, people respond to what the surrounding environment gives them. 

Accordingly, your behavior is a response to a stimulus that you are exposed to. So, the likelihood that you will repeat a particular behavior in the future depends on the consequence that follows such a behavior. 

Instrumental Conditioning Examples

One of the typical instrumental conditioning examples includes a teacher appreciating a student in front of other students for completing his assignment the best way. This will encourage the student to do his best in respect of his assignment each time to receive the teacher’s appreciation. 

Instrumental Conditioning in the Experiment 

The aim of the instrumental conditioning in this experiment was to make the horse learn to touch one of the two cones (desired behavior) indicated by the experimenter to receive the reward (desired outcome). The reward in this case is the pellets. 

Each of the horses was allowed to roam about freely in the box. Further, each of the experimenters sat 1m in front of the respective boxes. 

Also, each of the boxes had two cones, each of orange and white color respectively. These were 60 cm high and were placed on each side of the feed bucket. 

Now, the experimenter tapped on the top of the cone linked to the reward to give an indication to the horse. This was done for at the most 15 seconds or till the time the horse touched any part of the pointed cone. 

This way, as soon as the horse touched the pointed cone, the experimenter put a small number of pellets into the bucket. The horse was not rewarded when it touched the non-pointed cone. This way, a number of sessions were done and a number of correct responses and errors were recorded. 

Stage III: Pavlovian to Instrumental Transfer

PIT is the capacity of the Pavlovian signal that anticipates a reward to trigger or increase a response that is intended to derive the same reward. In this case, in a PIT session, the horses were tested under the condition of extinction. That is, the horses did not get any reinforcement. 

Various trials were done which included presenting CS (shaking the plastic jug continuously) separated by ITI periods and experimenters giving some number of signals (tapping the pointed cone). 

The effect of Pavlovian stimulus, that is shaking the plastic jug, on instrumental responding, that is the horses touching the feed bucket, was measured. This was done by counting the number of correct responses, that is horses touching the pointed cone. 

The incorrect responses, where the horses touched the unpointed cone, were also recorded. 

Temperamental Tests

Various temperamental tests were done on horses. These included novel arena test, passive human test, tactile sensitivity test, novel object test, social isolation test, novel area test, suddenness test, and locomotor test. 

Novel Arena test involved leading the horse to a test arena and leaving it there for 5 mins. Then, the experimenters recorded the number of neighs and defecations. These are taken as factors indicating fearfulness and gregariousness. 

Likewise, the sadness test involved opening the black umbrella suddenly in front of the horse while it was eating. The experimenter also placed the feed bucket containing pellets near the entrance of the arena. As the horse kept eating from the bucket until 3 seconds, the experimenter, not visible to the horse, suddenly opened the black umbrella and then recorded the flight distance in meters. 

Conclusion

The results concluded that horses who performed well during the PIT session were more sensitive to temperamental tests. That is, they neighed more during novel arena test or had greater flights distances in the sadness test. 

Thus, this study concluded that external signals can induce certain behaviors in horses. Also, it was observed that the magnitude of PIT was modulated to a great extent by individual temperament. 

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