Home Introduction to psychology DEFINITIONS OF INTELLIGENCE


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In Unit 5, we discussed how psychologists develop and test their theories. The unit also served to introduce us to other units in this course. You can now identify and explain steps in the scientific method. In addition, you can explain how a psychologist can test an hypothesis at 0.01 and 0.05 levels of significance. You are about to study another unit that you are likely to find relevant and interesting: Definitions of Intelligence. We will now consider conceptual clarification. Let us look at what other content you should learn in this unit as specified in the objectives below.

By the end of this unit, you should be able to:

  1. describe what intelligence is from the perspective of the layman; 
  2. define the concept of intelligence; and 
  3. explain the concept of intelligence quotient.


.1 Conceptual Clarification

Undoubtedly, ‘intelligence’ is a concept of theory and educational practice. Intelligence remains a major concern of psychology. Intelligence is an abstract noun. The early days of this century witnessed little usage of the term intelligence in psychology or in the classroom. According to Spencer and Galton, there is an important general ability which is super-ordinate to and distinct from special abilities. Burt equally accepted the theory of a general cognitive capacity that is probably dependent upon the number, complexity or connection of the organization of the nerve cells in the cerebral context. There was the technique of factor analysis which was introduced by Pearson at a time when Alfred Binet in France was working with French children of different pre-school and school ages to arrive at some answers explaining the underlying factors of the different performances of children at home and in school.

The importance of the general ability was strongly recognized in Britain and Europe while in the USA, it was questioned. The emphasis here was laid on the breakdown of the specific abilities explaining different types of activities and the performance of these activities.

3.2 Definitions

Of all the words used by professionals, no other word seems so clear when we hear it, and yet is so difficult to define, as intelligence. There is a massive research on the development of a child. Such research generates explanations on the definition of intelligence which for Piaget (1950:3) is ‘the concept of growth’. The concept of growth has been taken up by the environmentalists who claim that intelligence is not determined by heredity but by the type of environmental interaction in the history of early childhood. It is important for you to note that the type of environment and interaction will shape and determine a child’s adult .intelligence. But you must remember that all children, given the same history of environmental interaction, will attain the same level of intelligence in adult life (we will discuss more on this in units 7 & 8 of this course). The definition of intelligence based on the growth theory does not explain completely why there are some amounts of individual differences in cognitive behaviour. By implication, intelligence is also determined by heredity.

Of recent; prominent radical sociologists argued that the definition of intelligence is a socia1-class based one. They argued further that the differences in the social class origins of individuals compelled them to undergo differential environmental changes and hence differential levels of intelligent behaviour in later life. Had there been no differences in the class structures of societies, they argued then, the emphasis given on intelligence will most probably disappear as everybody will manifest the same level of intelligent behaviour eventually.

Also recently, there has been emphasis in the understanding of the definition of intelligence from psychological experiment and research evidence where the importance of parental attitudes toward education and of the home-background factors has been established. For example, Mukherjee (1972) showed that while attitudes towards mathematics and previous experience in mathematics explained most of the transferred task variance, intelligence was the least important factor in terms of the task explained.
I can see that you are more eager to learn about more definitions of intelligence. That is nice. Let us go on.

It is generally agreed that many degrees of intelligence exist, that even an imbecile exhibits some manifestations of intelligent behaviour. But when we refer to an intelligent person we mean only someone who is at the upper end of the distribution of I.Q. scores. Such an individual is one who exceeds a hypothetical cut-off point separating intelligent individuals from the general run of humans. Thus, although 1 e creativity undoubtedly varies along a continuum, only the rare individual who makes a singularly original (unusual) and significant contribution to art, science, literature, philosophy, government, and so forth, can be called a creative person. Note that a creative person is by definition a much rarer individual than the intelligent person. Thousands of intelligent individuals exist for every one who is truly creative.
If we observe events and behaviour which are concrete things as they can be e recorded and measured. Let us cite an example so that you can have a clear f understanding. We observe the difference between individuals of the same background, same chronological age and same previous history of learning in l problems-solving. If one individual solves the problem more quickly than the other, we say the former individual is more intelligent, thereby implying that the former individual has something to a greater degree than the latter. It is the ‘something’ that is called intelligence. Intelligence is therefore a kind of mental or cognitive ability which comes to play in problem solving.

Intelligence is also referred to as the reasoning ability of individuals. These reasoning abilities are of many types, for example understanding relations, comprehension of series, drawing analogies, completing patterns on the basis of symmetry and meaningful asymmetry, permutations and combinations, drawing inferences, understanding logic, deductive and inductive, verbal ability, and so on. We can therefore say that intelligence is a cluster of psychological traits. If valid instruments exist to measure these traits, then intelligence can as well be measured. Any trait or characteristic which is a continuum (continuous in nature) is amenable to statistical techniques leading to factor analysis. Thus when an experienced motor- car driver wants to negotiate a comer, he skips gear easily and the [mal function is still the same. The same technique is used by stenographers, textile workers, who usually produce more than their fellows.

According to Ryle (1952), there is no kind of performance or behaviour which can be described without qualification as ‘intelligence’. Confronted with such diversity in the nature of intelligence behaviour, it is not surprising that psychologists have often failed to agree on a comprehensive definition. Years ago, the editors of Journal of Educational Psychology, London, invited seventeen leading scholars to express their opinions on the nature of intelligence. While they achieved some agreement, nearly seventeen different definitions of intelligence emerged from this symposium (Thorndike, 195 1). Some of these definitions are:

The ability to carry on abstract thinking (Terman,1910).
The capacity to acquire capacity (Woodrow)
The power of good responses from the point of truth or fact (Thorndike,
1927). Vernon (1950) classified the description of intelligence as biological, psychological or operational.
Freeman (1936) classified descriptions of intelligence into those emphasizing:

1. Power of adaptation to the environment;
2. Capacity for learning;
3. Ability for abstract thinking.
Let us carry on our discussion.
Although modem psychologists know much more about mental abilities, the difficulty is far from resolved. One possible solution is to create a broad definition that addresses the complexity .of the word ‘intelligence’.

Wechsler (1975) is one psychologist who has attempted such a definition. He believes that intelligence is the capacity to understand the world and the resourcefulness to cope with its challenges. Much earlier, Wechsler (1958) suggested that intelligence is ‘the capacity to act purposefully, to think rationally, and to deal effectively with the environment’. By these broad standards, people act intelligently when they learn from past experiences, seek effective solutions to every day problems, and adapt to the world around them. Wechsler’s definitions provide a useful overview of the meaning of intelligence, but difficulties 5till persist. For instance, the issue of value judgment remains. Although Wechsler used broad terms-coping, resourcefulness, and rationality – they, all the same, imply particular values. You must remember that in any given culture different circumstances demand different types of coping and resourcefulness. Clearly, what is required of the ambitious distance learner undergraduate student is different from what is demanded of the child whose unemployed parents have been living in impoverished conditions for over a decade. We have many of such children in Nigeria particularly, and developing countries in general. Find out your level of understanding by trying your hands on this question.


  1. Will you describe yourself as intelligent? 
  2. Explain why you so describe yourself? 


In this unit, you have learnt how the layman describes intelligence, how psychologists define intelligence and what we mean by intelligence quotient. For example, the layman sees intelligence as the ability to do things correctly, while to the psychologists, intelligence is a psychological construct which implies the ability to carry on abstract thinking, the power of adaptation to the environment, and capacity for learning amongst others.


  1.  What you have learnt in this unit concerns descriptions and definitions of intelligence 
  2.  You also learnt that psychologists define intelligence differently.
  3. This enables us to have various definitions of the concept of intelligence some of which are stated below: a. What the intelligence tests measure (Berelson and Steriner, 1964), b. It consists of 120 .different abilities, (Guliford, 1980), c. It is the totality of an individual’s ability in solving problems of every day life, how best an individual succeeds is open to question (Alhassan, 1.981). 
  4. Intelligence quotient reflects the extent to which a child is mentally advanced or backward for his/her age. 


1 a. Two things that determine intelligence are:
i. …………………………………………………………………
ii. …………………………………………………………………
b. Define intelligence from the perspective of a sociologist.
c. Define intelligence from the standpoint of a psychologist.
d. Four reasoning abilities are:


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