Before Once the capsule was at rest at

Before researchers thought learning occurred by classical and operant only, although researchers later found there are biological constraints within conditioning. This contradicts the conditioning theory quite hugely and questions the effectiveness of reinforcement in behaviour.  Discovered by research on animals, studies (Shettleworth, 1975) & (Harlow, 1959) found animals have biological predispositions in some behaviours, hence disturbing conditioning.   

B.F. Skinner(1938) invented operant conditioning; where learning occurs through reinforcements and punishments. Expanding upon “law of effects” by Thorndike (1911), Skinner proposed, using reinforcers can shape animals to the behaviour they are being conditioned too. Reinforcers are a stimulus which follows a behaviour and increase probability it will occur; thus, reinforcement requires a response to occur. Additionally, reinforcement and punishment are key principles, both consisting of positive and negative. Positive reinforcement involves a desirable stimulus being added, whereas negative reinforcement is the removal of the aversive stimulus. Both reinforcements increase the likelihood of the behaviour. Furthermore, punishment is an undesirable consequence, which reduces likelihood of the behaviour. It has negative side effects, for instance, the maintenance of undesirable behaviours. Another concept in the theory is schedules of reinforcement; it is how often a response is reinforced. Affecting how quickly or slowly something is learnt and whether extinction occurs or not.

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Research by Breland and Breland(1961) found natural behaviours of gathering or preparing food, overrides the influence of trained behaviour. Hence supporting biological constraints being in operant conditioning.

Procedure: A random selection of animals, from a sample of 6,000, conducted different tasks. The tasks involved the positive reinforcement of food and the schedules of reinforcement consisted of the animals being rewarded after successfully completing the task. One task involved a raccoon having the predicted reinforced response of picking up coins and putting it in a 5-inch metal box. Afterwards, it receives positive reinforcement (food). It consisted of two conditions, one with a single coin and the requirement of dropping it in, then attempt with 2 coins later.

Another task involved a chicken, where the reinforced response was to pull rubber loop, releasing capsule to roll down a slide. Once the capsule was at rest at the bottom of the slide, the chicken had to peck it towards the observer. If successful, an automatic feeder reinforced the behaviour. However, before adding the loop, the chickens pecked stationary capsules until pecking behaviour was strong enough to push towards the observer.

Lastly, the pigs’ observation occurred over several weeks and involved timing how long it took to put wooden coins in the bank and retrieve others. The predicted reinforced response was picking up a coin and putting it in the bank, then getting another coin and so on, until the ratio was complete. Being completed neatly and quickly.

Results: Animals did not demonstrate the conditioned behaviours, despite the reinforcement hence showing failure of the conditioning theory. The racoons would not let the coin go, rather would rub it against the inside of the container and clutch it for a few seconds. Finally, it gave the coin back. Though, with two coins the rubbing behaviour got worse, despite the non-reinforcement. At first, the chickens completed it successfully but later, the chickens dragged the capsule to the cage and pounded it up and down on the floor of the cage. Additionally, some chickens could not peck the stationary capsules successfully. Lastly, the pig quickly and neatly took the coin and put in it in the bank. Although after few weeks the behaviour was slower; on the way back from the bank it would drop the coin, root it, then toss it in the air and drop it again and so on. It was not due to low drive, it occurred despite having strength and increased drive. The pig went through the ratio slowly, taking 10 minutes to transport four coins in six feet.


Discussion: These results developed an aspect of biological constraints, “instinctive drift”, where learned behaviour, overtime, drifts towards instinctive behaviour (Breland& Breland, 1961). While preventing the hungry animal from food reinforcement, instinctive drift still occurred. Hence, it went against years of research into the principles of learning, which stated, rewarding behaviour with food reinforcement increases the strength of behaviour. Whereas eliminating undesired behaviours which resulted in no food reinforcement.


Conclusion: Overall, there is overwhelming evidence of biological constraints in operant conditioning. Therefore, in future research or therapies involving conditioning of any species, the acknowledgement of the evolutionary history and their instinctive patterns is vital. Otherwise, conditioning can fail as animals could go back to biologically predisposed behaviours.