Faculty theory of intelligence:

This is the oldest theory of intelligence given during the period of pre-experimental psychology. According to this theory mind is made up of different faculties like reasoning, logis, memory, imagination and discrimination. These faculties are independent of each other and can be developed by rigorous mental exercises of the difficult subject-matter.

This theory does not take the hereditary factors of intelligence into account and thus this theory was discarded by the later psychologists who believed that we can never improve the intellectual capacity of a person if he is mentally slow by birth.

Unifactor theory:

According to Alfred Binet (1916) intelligence is a general intellectual ability which is made up of several discrete abilities. These abilities include 

(i) to reason well with abstract material

(ii) to comprehend well

(iii) to have a clear direction of thoughts

(iv) to relate thinking with the attainment of a desirable end and

(v) to be self-critical.

All these abilities combined together is called general mental ability. Thus, intelligence is a single but complex mental process which can be measured by different kinds of materials designed for the purpose.

Two factors theory:

This theory was developed by an English psychologist, Charles Spearman in 1904. According to him, intellectual abilities consist of two factors. general ability known as ‘G’ factors and specific abilities known as ‘S’ factors.

Characteristics of G factors

(i) It is universal inborn ability.

(ii) It is general mental energy.

(iii) It is constant, i.e., it remains the same in all the individuals and does not change with time,

(iv) The amount of G differs from person to person depending on his genes.

(v) It is used in every life activity.

(vi) Greater the amount of G in an individual,larger is the chance of his success in life.

Characteristics of ‘S’ factors

(i) It is learnt and hence acquired in the environment

(ii) It varies from activity to activity in the same individual.

(ii) The amount of S also differs from person to person due to his accessibility to learning situations.

(iv) ‘S’ factors are related to the specific activity. A low correlation between two or more functions or activities indicates the presence of ‘S’ factor involved in the activity. A person can be expert only in one or few activities because of the specific factors involved in the activity.

According to Spearman, out of these two factors ‘G’ factor is more important and thus it is an important measure of intelligence. So, any intelligence test should measure only “G’ factor because it provides most important basis of predicting a person’s behaviour in different situations. Raven’s Progressive Matrices and Catell’s Culture Fair Test both measure ‘G’ factor.

Spearman has explained his theory with the help of a tetrad equation which is given below :

rap x rbą – raq x rbp = 0

Here,a = opposites b = discrimination P = completion q = cancellation

Thus, rap means correlation between opposites and completions, rbq means correlation between cancellation and discrimination, raq means correlation between opposite and cancellation and rbp means correlation between discrimination and completion. This theory can also be explained with the help of a diagram given below :

Multi-factors theory :

This theory was developed by an American psychologist, E.L. Thorndike. He opposed the theory of general intelligence by saying that there are specific stimuli and specific mental responses. Intelligence is nothing more than a potential specific connections between these stimuli and responses. Differences of intelligence among people are due to the different number of such connections in the neurological system. This theory is also called atomistic theory of intelligence. There are four attributes of intelligence according to him:

  •  Level : It refers to the difficulty of a task that can be removed by using intelligence. If different tasks are arranged in increasing difficulty order, then the height that a person can attain determines his level of intelligence. It is a kind of power test.
  • Range : It refers to the number of tasks of the same difficulty value that a person can do in  a certain period of time. Theoretically, an individual possessing a certain level of intelligence should be able to solve the whole range of tasks at a given level. It is a kind of speed test. Range and level can not be completely isolated from each other. We can not measure range without altitude (level) and vice versa.
  • Area : It refers to the total numbers of situations at each level to which the individual is able to respond. Area is the summation of all ranges at each level of intelligence. Area = Level x Range.
  • Speed : It refers to the rapidity with which an individual can respond to a test items. Speed and level are positively correlated. It is different from range in the sense that no specific time is given here to complete a task. Every intelligence test should consist of these four attributes.

Group factor structure of intelligence (PMA Test) :

This theory was developed by L.L. Thurstone. According to him, intelligence is not an expression of general factor but a combination of group of traits. They are intermediate factors, i.e., they are not so universal as ‘G’ factor and they are not so specific as ‘S’ factor. This primary group of factors give the common mental abilities, a functional cohesiveness and then constitute a group. Another group of common mental abilities is said to have another primary factor and so on. In this way, there are a number of groups of mental abilities each of which has its own primary factors. On the basis of factor analysis of these groups, Thurstone identified the following seven group factors which are termed as primary mental abilities (PMA).

1. Number factor (N): It is the ability to do numerical calculations rapidly and accurately.

2. Verbal factor (V) : They are related to the operations involving verbal comprehension.

3. Space factor (S): It is related to the tasks in which subject manipulates an object imaginary in space.

4. Word fluency factor (W): It is involved to the situation when the subject is asked to think of isolated words at a fast rate.

5. Reasoning factors (R): It is used in those tasks that require the subject to discover a rule or principles involved in series or groups of letters.

6. Rote memory (M): It is the ability to memorize a fact quickly.

7. Perceptual speed (P): It is the ability to note perceptual (visual) details rapidly. The point to be noted here is that these seven abilities are significantly correlated with each other.

Structure of intelligence (SI) model :

This model was given by J.P. Guilford in 1966 in the University of California on the basis of factor analysis of many tests. According to him human mind is composed of at least three dimensions-operations, contents and products, and each dimension of intellect is sufficiently distinct which can be detected by factor analysis. These three dimensions of mind are given below:

Operations : Operations can be divided into five major groups of intellectual abilities.

  • Cognition : It includes discovery,recognition of informations and new understanding of the facts.
  • Memory : It is the ability to recognize or recall previously learnt material.
  • Divergent thinking : This operation is closely associated with creative potential. It refers to the ability to search out and think in a novel out of track way.

  • Convergent thinking : It refers to the generation of information from given information and drawing conclusion from the given facts.
  • Evaluation : It is the ability to make judgement on the basis of merits and demerits of a phenomenon. Here, value judgement on knowledge and thoughts is placed after critically examining them.

Contents : Five kinds of contents are involved here. Operations are performed on these contents.

  • Figural content: It is the concrete material perceived through the senses. Visual materials have three properties, size, form and colour.
  • Auditory content: It includes nature and characteristics of sound perceived. .
  • Symbolic content : It includes letters, digits and other conventional signs usually organised in general pattern.
  • Semantic content: It refers to those verbal meanings, ideas and concepts for which no examples are necessary
  • Behavioural content : It includes knowledge regarding other persons.

Products : When five operations are applied to five types of contents, six kinds of products are made.

Units : It refers to the production of a single word, definition or isolated bits of informations.

Classes : It refers to the production of a concept.

Relations : It refers to the production of any form of relationship, such as, analogy, opposite or similar ones.

System : It refers to the production of internally consistent set of classification of various forms.

Transformation : It refers to the production of changes in meaning, organisation or some other arrangement.

Implication : It refers to the production of such information which is beyond the data given.