Psychology of Individual Differences
1. Meaning and Definition
There is no end to variations and deviations in both living and non-living creations. From types of soil and rocks to the quality of water, differences exist everywhere. In the human species, even identical twins are not exactly the same.
Dictionary of Education (Carter B. Good, 1959):
- Definition A: Variations or deviations among individuals in regard to a single characteristic or a number of characteristics.
- Definition B: Those differences which in their totality distinguish one individual from another.
Worked Definition: The differences among individuals that distinguish or separate them from one another and make each a unique individual.
2. Specific Types of Individual Differences
Variations are broadly classified into Physical/Physiological and Psychological categories.
PhysicalDifferences
These relate to the biological makeup and observable bodily traits of an individual.
Physical Differences
Height, weight, color of skin, eyes, and hair, size of limbs, facial expressions, and internal organ functioning.
Motor Ability
Reacting time, speed of action, manual dexterity, speech mannerisms, and resistance to fatigue.
Psychological Differences
These encompass mental processes, personality traits, and acquired behavioral patterns.
Mental & Intellectual
Reasoning, thinking, and imagination. Intelligence spans from Idiot/Imbecile to Very Superior/Genius.
Achievement
Knowledge and proficiency levels vary even among those with similar intelligence and schooling.
Emotionality
Prominence of positive vs. negative emotions; levels of emotional stability vs. immaturity.
Interests & Aptitudes
Preferences for social vs. solitude; mechanical, musical, scholastic, or artistic natural leanings.
Attitudes & Beliefs
Conservative/rigid vs. progressive/liberal views regarding social, religious, or political life.
Learning Style
Ease of learning, memorization methods, and the suitability of specific study environments.
Social & Moral
Levels of social adjustment (properly adjusted vs. anti-social) and the development of ethical sense.
3. Distribution of Individual Differences
Distribution in nature follows the pattern of a Normal Probability Curve (NPC) or “Bell-Shaped Curve”.
68.26%
The Normal/Average Majority
Found near the mean value.
15.74%
Above Average
Significant positive deviation.
15.74%
Below Average
Significant negative deviation.
Example: In a sample of 10,000 students, roughly 6,826 will be average, while 1,574 will be above average and 1,574 below average. Intelligence follows this: most fall between 90-110 IQ, while Geniuses (140+) and Idiots (below 40) are rare.
4. The Role of Heredity (Nature)
Heredity is the biological transmission of traits from parents to offspring through genes. All the qualities that a child has inherited from the parents is called heredity.
Father of Heredity
Gregor Mendel is recognized as the Father of Heredity. He propounded three fundamental laws:
- Law of Dominance: When two different alleles are present, one “stronger” trait (dominant) hides the “weaker” one (recessive).Example: If you cross a Purple flower with a White flower, all the babies are Purple because purple is dominant.
- Law of Segregation: Every parent has two copies of a gene, but they “split up” so the parent only passes one copy to their child. Example: A person with one “Brown eye” gene and one “Blue eye” gene will pass the Brown gene to 50% of their kids and the Blue gene to the other 50%.
- Law of Independent Assortment: Different traits (like height and hair color) are inherited separately; getting one trait doesn’t automatically mean you get the other. Example: A pea plant can be Tall with Green seeds or Tall with Yellow seeds—the height doesn’t “stick” to a specific color.
Hereditary Limits
Heredity provides the basis for personality development and sets both the Upper Limit (highest potential) and Lower Limit (minimum capacity).
The Biological Code
DNA (Deoxyribonucleic Acid): A molecule that contains all the instructions needed for an organism.
Genetics: The study of heredity and the variation of inherited characteristics.
Chromosomes: Long, thread-like structures made of DNA and proteins.
Mechanism of Conception
- Conception: Occurs at the time of conception when male and female germ cells unite, causing fertilization of the ovum. The fertilized egg is known as a Zygote.
- Chromosomes: Each human cell has 46 Chromosomes (23 pairs). 23 from the father’s sperm and 23 from the mother’s egg.
- Genes: The basic unit of heredity, made up of DNA. Over 1,000 genes exist per chromosome, carrying instructions for making proteins.
Genotype
Refers to the specific genetic makeup of an individual consisting of the combination of genes inherited from parents. It is not directly observable (e.g., Genetic Code).
Phenotype
Refers to the observable characteristics of an individual, including physical traits (height, eye color) and behavioral traits. It is influenced by both Genotype and Environment.
Sex Determination
The 23rd pair of chromosomes determines the sex of the child. 22 pairs are known as Autosomes.
- Female (XX): Result of X from mother and X from father.
- Male (XY): Result of X from mother and Y from father. The Father is biologically accountable for sex determination.
Birth of Twins
- Develop from a single fertilized egg that splits into two embryos.
- Share 100% of their DNA.
- Always the same sex and look very similar.
- Develop from two different eggs fertilized by two different sperms.
- Share about 50% of their DNA.
- Can be the same or different sexes; may look similar or different.
Genetic Disorders
Trisomy-21 (Down Syndrome)
Caused by an extra copy of chromosome 21 (embryo has 47 chromosomes). Features include intellectual disability, developmental delays, and distinct facial features.
Turner Syndrome
Affects only females; occurs when one of the X chromosomes is missing or partially missing. Features include short stature, webbed neck, and heart/renal anomalies.
5. The Role of Environment (Nurture)
The environment is everything that affects the individual except his genes. Environment is Dynamic in nature, while Heredity is Static.
Internal (Prenatal)
Includes all external factors and experiences that impact an individual after conception, such as the mother’s health and diet.
External (Postnatal)
Consists of physical, social, moral, economical, political, cultural, and emotional forces that influence development.
Educational Impact: Teachers should provide the best mental environment so a child can flourish and reach their full potential.
6. Relative Importance & Interaction
Today, most psychologists believe that development is an interaction between Nature (Heredity) and Nurture (Environment). Both are equally essential in the growth and development of the child.
Analogies for Interaction:
- Seed & Soil: Heredity is the seed (potential); Environment is the soil (nourishment).
- Rectangle: Personality is the area; Heredity is the length, Environment is the breadth.
- Capital & Investment: Heredity is the working capital; Environment is the opportunity to invest.
7. Educational Implications
Teachers must realize that every class contains a mix of superior, average, and dull students. Individual differences provide the basis for personality development.
Provisions for Schools:
- Assessment: Use intelligence tests, interest inventories, and cumulative record cards.
- Ability Grouping: Form homogeneous groups to adjust instruction methods.
- Flexible Curriculum: Diversified courses and co-curricular experiences.
- Individualized Plans: Adoption of the Dalton Plan, Winnetka Plan, or Project Method.
- Practical Measures: Small class sizes, individualized home assignments, and special coaching for both gifted and dull children.
Quick Practice: Individual Differences
Hover over “Explanation” for answers.