Individual Variation: Meaning & Causes

PsychologyPersonality Psychology

All humans are different from each other in terms of physical features as well as behaviours. In psychology, these differences are referred as individual variations. By definition, individual variations are the uniqueness and variety among people's traits and behavioral tendencies. These persistent traits separate one person from another and remain constant across time and in many circumstances and define that organism.

What is the Meaning of Individual Variations?

The individual variations are the primary and essential characteristics of every human being. There are different characteristics of human beings that every human possesses, such as, intellects, behaviours, attitudes, etc., but the nature of these characteristics in every human is different. Among all, the intellectual variation, is most prominent. To understand it better, two perspectives are defined i.e. trait point of view, these differences can arise from different genetic materials they inherit, giving them varied mental capabilities. And, the second one is - behavioural viewpoint, these differences can be the active information processing governed by various environmental factors. The centuries old nature vs. nurture debate is another approach to define the individual variations.

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Individual variation in IQ

The intelligence quotient is a standard measure of an individual's intelligence level based on psychological tests. Alfred Binet and Theodore Simon developed the first IQ test in 1904, later Lewis Terman used that in 1916 and named it as the Standford Binter Intelligence Test. Like many traits, IQ is believed to follow the normal distribution; a probability distribution that is symmetric to the mean, showing that data near the norm are more frequent in occurrence than data far from the mean. This indicates that while very few people have extremely low or extremely high IQ, most people have average intelligence.

The mean IQ of the population is 100, and people with the intelligence of 90-110 have normal intelligence. The population in the extremes is referred to as an atypical population. According to Fisher (1925), an atypical population in a continuum lies above 5% of the scores two standard deviations from the mean. The five percent are divided by IQ scores on both sides to determine the abnormal population in terms of intellect. M = 100 and SD = 15, the IQ cut-off for giftedness is thus 130 and for intellectual impairment is 70.

Giftedness − Giftedness is an exceptional general aptitude that manifests in outstanding performance across various endeavours. The term "talent" describes a unique skill in a particular area. Gagne (2000) defined giftedness as "the possession and application of superior natural skills, in at least one ability area, that are untrained and spontaneously shown, to the extent that an individual rank in the top 10% of his or her age peers." The definition does not follow the criteria of Fisher. Compared to other children or young people, their age, experience, or surroundings, the gifted children or adolescents exhibit surprisingly high degree of accomplishment, as they −

  • Exhibit high-performance capability in an intellectual, creative, or artistic area;
  • Possess an unusual capacity for leadership; and
  • Excel in a specific academic field.

Intellectual Disability − Intellectual disability is characterised by issues with general mental abilities that influence normal functioning in two areas: intellectual functioning (such as learning, problem solving, and judgement) and adaptive functioning. It is further subdivided into−

  • Mild retardation (IQ – 55 to 70) − This group accounts for around 85 percent of the mentally retarded individuals. They exhibit early indicators of delayed development in terms of learning to walk, talk, feed, and toilet themselves, normally after a year than the usual child. Compared to normal people, mildly retarded people exhibit immature behaviour, weak impulse control, weak decision making power, and are unable to anticipate the implications of their acts. They can be expected to attain a decent level of educational accomplishment with early diagnosis, parental assistance, and special programs.
  • Moderate mental retardation (IQ – 40 to 55) − This category includes around 10% of all mentally impaired people. They appear inconvenient, have poor motor coordination, and have pleasant, bland, and sometimes doubtful personalities. Like the mildly retarded, they are considered trainable rather than educable due to their poor development and deficient talents and abilities. Depending on their overall adaptive behavioural level, they require regular supervision and care and institutionalization.
  • Severe mental retardation (IQ – 25 to 40) − This category includes nearly 3.5 percent of all retarded people, most of whom are children and adolescents. They have the severe motor and verbal disabilities and grossly impaired development from birth to infancy. Most of them show little interest in their environment, and many never acquire basic skills and functions like feeding and clothing or bladder and bowel control. They may benefit from good care, prompt treatment, and specialized training to manage their physical well-being and perform manual labour.
  • Profound mental retardation (IQ – Below 25) − This category accounts for 1.5 percent of the total mentally impaired population. They are significantly lacking in both intellectual abilities and adaptive conduct. They cannot protect themselves from common risks, manage their affairs, or meet physical demands. Their life duration is too short as a result of their low resistance. Essentially, they must be institutionalized when their condition deteriorates due to their parents' biased attitude and the severe demands of their environment.

Other variations in intelligence

The variations can also arise because of other factors such as sex, socioeconomic status, or home environment.

  • Sex − Men and women have comparable intelligence, but men have more intellectual diversity than women. Girls and women perform better on activities requiring verbal expressiveness and fluency, quick and accurate perception of details, and rapid, correct physical actions. Boys and men better in terms of spatial, numerical, and mechanical skills.
  • Home environment − Home characteristics appear to be related to disparities in mental capacity. Interaction with caregivers is critical throughout the first years of life to promote optimal psychosocial development of children. A lack of stimulation is related to early social and cognitive disadvantage. Furthermore, the ratio of encouraging to reprimanding statements delivered to youngsters affects intellect.
  • Socioeconomic status − Socioeconomically advantaged groups perform better on intelligence tests. A cycle is continued in which some groups live, work, and raise their children in considerably more conducive environments to intellectual advancement than others. Despite efforts to integrate schools, jobs, and neighbourhoods, we still have a caste system in some ways. Even when socioeconomic status is essentially equivalent, the cultures of some communities remain strikingly different and plays an important role.
  • Physical activity − Besides these social influences, physical activity also influences intellect. It helps children create and consolidate memory, it also helps the elderly to maintain intelligence for executive tasks like planning and organizing mental procedures.

Giftedness vs Talent − Professor Françoys Gagné is a French-Canadian educational psychologist who developed the 'Differentiated Model of Giftedness and Talent (DMGT),' a comprehensive model for gifted students. This model is a perfect example of the role of environmental factors in intelligence. DMGT model illustrates how the specific expert skills (talents) emerge from innate abilities (gifts).

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It identified six components that work together to promote this process: gift (G), chance (C), environmental catalyst (EC), intrapersonal catalyst (IC), learning/practice (LP), and talent (T).


Human diversity, in terms of physical and behavioural features, is visible and unavoidable. Such variations exist in intellectual capabilities, differences in general intelligence, and in specific abilities. Although studies and theories have focused more on differences in general intelligence, but it has certain limitations. The most important is that IQ tests are usually not meant to illustrate this within-person development, but rather to determine the relative degree of developed cognitive qualities for a given stage of development. And, this consideration will lead to better evaluations of mental abilities.

Updated on 13-Oct-2022 11:19:47