Trial-and-Error Learning Theory

E. L. Thorndike
The experimental study of animal learning by E. L. Thorndike (1874-1949) in the United States and his theory on trial-and-error learning provided the impetus for Skinner's experiments on instrumental or operant conditioning. Thorndike's doctoral research on 'Animal Intelligence' in 1898 provided the psychological world the first miniature system of learning known as trial-and-error learning. 

Trial & Error is based on random activities to reach the goal. Thorndike's research on animals showed that learning is a matter of connecting responses to stimuli in a very mechanical way. There is no involvement of consciousness, thinking, reasoning or understanding. The animal performs responses mechanically. The responses that bring reward are learned; the responses that do not bring reward are not learned. The animal does not show ability to understand, think, and reason. The animal learns mechanically through trial-and-error.

Indeed many forms of human learning, particularly the learning of sensory- motor skills, are achieved through trial-and-error. Learning to walk, to swim, or to ride a bicycle is based on trial-and-error. At the beginning, we make wrong movements and commit errors. As we go through a series of practice trials, errors are reduced and responses are mastered. The gradual reduction of errors over trials gives the name, trial-and-error form of learning.

Thorndike’s Experiment on Cat:


Thorndike's Puzzle Box
His classic experiment used a hungry cat as the subject, a piece of fish as the reward, and a puzzle box as the instrument for studying trial-and-error learning.

In this typical experiment, a hungry cat was placed inside the puzzle box, and a piece of fish was kept outside the box. The cat could not reach the fish unless it opened the door. In order to escape from the box, the cat had to perform a simple action as required by the experimenter. The cat had to pull a loop or press a lever in order to open the door. Once the door was opened, the cat could escape and get the fish as a reward. 

First Trial:

Hungry cat is placed inside the box. Fish kept outside the box work as a motive. Cat started doing random movements for getting food. Cat squeeze through opening, claws and bites at the bars of wires, thrust its paws through any opening. All the irrelevant responses continued for several minutes until the cat hit upon the correct response, by chance. Hungry cat came out and got its reward i.e. fish.

Second Trial:

Hungry cat placed in a puzzle box. Fish kept outside the box worked as a motive. To get out of the box cat again did random movements. But cat took less time to come out from the box. 

With increasing trials, the time taken to pull the loop (response latency) decreased. The wrong responses (errors) that the cat was showing also decreased, as trials increased. Finally, the cat learned the trick. As soon as it was put in the box, it pulled the loop to escape for a well-deserved reward. The name, trial-and-error learning comes from the fact that errors decreased over trials. The cat learned from its errors.


Experiment sums up the following stages in the process of learning:

Trial & Error is based on random activities to reach the goal. Random activities are block or hinderances, drive, goal, random movements, multiple response, chance, success, selection and fixation.
  1. Drive: Hungry cat intensified by the sight of the food.
  2. Goal: To get food by getting out of the box.
  3. Block: The cat was confined in the box with a closed door.
  4. Random movements: The cat persistently tried to come out of the box without knowing how.
  5. Chance success: Striving and random movements the cat by chance succeeded in opening the door.
  6. Selection: Gradually cat recognized the correct way to manipulate the latch.
  7. Fixation: At last cat learned the proper way to open the door by eliminating all the incorrect responses &    fixing only the right response.

Thorndike's Laws of Learning:


1) Law of Effect:


According to the law of effect, responses that are immediately followed by a satisfactory outcome become more strongly associated with the situation and are therefore more likely to occur again in the future. Conversely, responses followed by negative outcomes become more weakly associated and less likely to reoccur in the future.

If the behaviour is followed by something positive = it will get repeated and strengthened 
If the behaviour is followed by something negative = it will get weakened and will not be repeated.

2) Law of Recency:


The most recent response or any behaviour or activity which is happened recently is most likely to reoccur. According to this law what is learned most recently is remembered best. And that is why those reviews right before the test are so very important.

3) Law of Frequency:


According to the law of frequency, the stimulus-response (S-R) associations are strengthened through repetition or weakened through lack of repetition. Any activity or behaviour which is repeated many times, becomes permanent. 

4) Law of Exercise:


Sometimes the law of recency and the law of frequency together is called the law of exercise. It has two parts; the law of use and the law of disuse.
  • Law of use- the more often an association is used the stronger it becomes.
  • Law of disuse- the longer an association is unused the weaker it becomes.


Reference: 
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