The most important variable that affects schooling or performance on a job is intelligence. Psychologists have interpreted the term intelligence in different ways and there is no consensus among them on the term even so far. In psychology this term is treated as a construct whose structure is different in different individuals.

The vagueness of the term arises due to the fact that intelligence is not a concrete material. It is rather abstraction from the behaviour of the individual which is indirectly inferred and elaborated as an adjective. The dictionary meaning of term “intelligence” is the capacity to acquire and apply knowledge. Boring defines intelligence as intelligence is what an intelligence test measures.

Definitions of Intelligence

Several psychologists have classified and defined intelligence in several ways. Some of them are given below:

1. Vernon’s Classification of Intelligence

(a) Biological Approach: Man is an organism among millions living on earth. Environment works as a foe for him. Intelligence is the capacity to adapt to the environment or new situations of life at every moment. This definition of intelligence can be criticized on the ground that there have been many intelligent and renowned persons who were ill adapted to their social and physical environment. Besides, if we want to study individual differences in a society, this definition serves no practical purpose. (b) Psychological Approach . According to psychologists intelligence is the relative effects of heredity and environment both. An English psychologist, C. Burt defined intelligence as the innate general cognitive ability. In support of psychological definitions of intelligence Hebb and R.B. Catell distinguished two kinds of intelligence. The first is intelligence “A” which is Fluid intelligence and which is related to genetic potentialities or innate qualities of the individual’s nervous system. Second is intelligence “B” which is crystalised “intelligence” and which is related to experiences, learning and environmental factors. These two types of intelligence in normal circumstances so much overlap on each other that they are practically indistinguishable.

(c) Operational Approach : These definitions help us to understand the concept of intelligence in clear and definite terms. In this approach scientific terms are first of all defined operationally and then observations are conducted with reference to these terms. For example, in order to determine a child’s IQ, we first administer a test of a specific kind. Then we observe his performance on the test and finally draw certain conclusions in the context of the pre-determined objectives.

2. Freeman’s Classification

(a) Ability of adjustment : An individual is intelligent to the extent to which he is able to adjust to new situations and problems of life. The more a person is intelligent, the more he is able to adapt to his environment in antagonistic conditions. The person who is low in intelligence has less capacity to adjust to the new situations of life.

(b) Ability of learning : Learning ability is also an index of intelligence. The more a person is intelligent, the more he will be able to learn new things.

(c) Ability to carry on abstract thinking : This category of definitions of intelligence is related to the effective use of concepts and symbols in dealing with situations and solving the problems through the use of verbal and numerical symbols. According to Terman, an individual is intelligent to the extent he is able to carry on abstract thinking.

3. E.L. Thorndike’s Classification

(a) Concrete intelligence : The intellectual ability in relation to concrete materials is called concrete intelligence. It is the ability of a person to comprehend the actual situations and react to them adequately. This kind of intelligence is measured by using performance tests or picture tests in which the subject manipulates the concrete materials.

(b) Abstract intelligence : It is the ability to respond to words, letters, numbers or symbols. This type of intelligence is required in all academic activities in schools or outside the schools. The highest level of abstract intelligence is manifested in the thoughts of philosophers or in the inventions of scientists and mathematicians.

(c) Social intelligence : It is the ability of an individual to react to social situations of life. It is the ability to understand others and to react to them in such a manner that they may not feel unjust attitude regarding them 

4. Intelligence as a Global Capacity

A comprehensive definitions of intelligence :Stoddard (1943) and Wechsler (1944) have defined intelligence in the following words : “Intelligence is the aggregate or the global capacity of the individual to act purposefully, to think rationally and to deal with the environment effectively”. Stoddard further elaborated that intelligence is the capacity of a person to undertake such activities which are: (i) difficult (ii) complex (iii) abstract (iv) economical (v) goal directed (vi) valuable from social view points (vii) original. These activities demand concentration of energy and a resistance to emotional forces.

Characteristics of Intelligence

From the above definitions of intelligence, we can draw the following characteristics of intelligence:

(i) Intelligence is the composite of several intellectual skills, such as thinking, doing, reasoning, dealing, learning etc.

(ii) Intelligence is displayed by the behaviour of the individual as a whole and intelligent behaviour is always goal directed.

(iii) Intelligence is the ability to adjust to abnormal and challenging situations of life.

(iv) Intelligence is not related to ordinary tasks of life. It is always related to extra ordinary manipulation.

(v) Wechsler has included the concepts of drive and incentive which are implied in his statement. “To act purposefully” and “to deal effectively”. But many psychologists are of the view that drive and incentive are nonintellectual traits of personality and if they are included in a test of mental ability, more confusions will be created thereof.

(vi) There are seven fundamental elements of intelligence according to Stoddard. Intelligent person can undertake difficult and abstract tasks with ease. He can manipulate and deal the abstract ideas and concepts efficiently. Similarly, economy refers to the rate at which a mental task is done or a problem is solved. If “A” solves a problem sooner than ‘B’ then ‘A’ will be considered more intelligent than ‘B’. The term social value indicates whether a mental task performed by a person is in accordance with the socially desirable and acceptable norms or not. The last term original refers to a person’s, ability to discover something new and different, i.e., this term is directly related to creative potential of a person. Discovery of some new facts and principles and inventions of new concrete materials by the scientists are few examples of originality.

Stoddard’s definition of intelligence has been criticized on two grounds:

(a) It includes social values in intelligence, i.e., intelligent task must be socially desirable. Psychologists criticize this point by saying that social value is a subjective phenomenon, i.e., what is desirable for me, may not be necessarily desirable for others. So, there is no scope of subjectivity in an objective intelligence test.

(b) He has included two conditions of intelligent behaviour in his definition, First is concentration of energy and second is resistance to emotional forces. Psychologists say that these elements are non-intellectual traits and hence they should not be included in mental abilities at any cost.