Edward Thorndike was an influential psychologist who is often referred to as the founder of modern educational psychology. He was perhaps best-known for his famous puzzle box experiments with cats which led to the development of his law of effect.

Thorndike's principle suggests that responses immediately followed by satisfaction will be more likely to recur. The law of effect also suggests that behaviors followed by dissatisfaction or discomfort will become less likely to occur.

Thorndike’s multifactor theory of intelligence is at one extreme of the interpretations regarding the nature of mental organization. According to this intelligence is said to be constituted of a multitude of separate factors, or elements, each one being a minute element of ability. Any mental act, according to this theory, involves a number of these minute elements operating together. Any other mental act involves a number of the element in combination. Thorndike’s theory has been said to be an “atomistic” theory of mental ability. (Freeman,1965). Opposed to Thorndike’s theory of the nature of intelligence is Spearman‟s two factor theory, which stands at the other extreme of interpretations. According to him all intellectual activity is dependent primarily upon and is in expression of a general factor as mental energy. They concluded that the principal distinguishing characteristic of test highly “loded” with general factor(g) is that they require insight into relationships--what he called “the education of relations and correlates”.

He argued that instead of generality of intelligence, communality in the acts of people to perform intelligently needed to be looked into. According to Thorndike, the common element does not reside in the individual but in the nature of the tasks themselves. People differ in their ability to perform any specific act in terms of the level of difficulty they can manage. They also differ in the range or number of tasks they can or cannot perform. For Thorndike, intelligence was more like a series of skills or talents and several or many tasks might call for the same kind of ability. According to him, the correlations between various tests are the result of the fact that the tests have features in common with each other even though they are called as measures of different aspects.

Thorndike’s contention that there is no general intelligence but very specific acts has, however, does not hold water in view of the fact that some tasks have so many elements in common that it is desirable to classify them into groups such as arithmetical reasoning, visual perception, word meaning, analogy, etc.

Thorndike has classified intellectual activity into three broad types:

(i)                 social intelligence,

(ii)              concrete intelligence, and

(iii)            abstract intelligence.

However, this is a classification of the type of tasks and not an analysis of mental organisation itself. One can notice that the discrepancy of point of view between Spearman and Thorndike is basically a theoretical one and the types that interested Thorndike are essentially the same as the measures which Spearmen used in his correlation matrix.