(a) Ravi has been showing signs of extreme social withdrawal and erratic mood swings. As a psychology student,

Question

Q. (a) Ravi has been showing signs of extreme social withdrawal and erratic mood swings. As a psychology student, how would you apply different approaches/models/factors to understand and explain any abnormal behaviour?

(OR)

(b) Psychological Disorders have come a long way in their journey of understanding and treatment of disorders. To understand psychological disorders, we would require a brief historical account of how these disorders have been viewed over the ages. When we study the history of abnormal psychology, we find that certain theories have occurred repeatedly. Trace the history of disorders to understand their origin and leading to the latest developments.

CBSECBSE Class XII Board 2026Subjective· 6mImportance★★★★★

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Part (a)Concept understanding — Abnormality Definition

Abnormality Definition — First Principles

Imagine you are looking at a set of data points — say, the heights of all students in your class. Most heights cluster around some average value. A few students are taller, a few shorter, but almost everyone falls within a certain range. Now suppose one student is 8 feet tall. That student's height is abnormal — it lies far outside the pattern of the rest of the group.

That is the core intuition behind abnormality in statistics: an observation that deviates so much from the rest of the data that it stands out as unusual.

The Precise Definition

In formal terms, an abnormality (often called an outlier) is a data point that lies at an abnormal distance from other values in a random sample from a population. There is no single universal cutoff — it depends on the context — but the most common working definition in Indian exam syllabi (especially for statistics and probability) is:

\text{An observation } x \text{ is abnormal if } |x - \mu| > 3\sigma

This is the 3-sigma rule. The reasoning: for a normal (bell-shaped) distribution, about 99.7% of all data lies within three standard deviations of the mean. Anything beyond that has less than a 0.3% chance of occurring naturally — so we call it abnormal.

Why 3-Sigma? The Intuition

The number 3 is not arbitrary. In a normal distribution:

Within 1σ of μ: ~68% of data
Within 2σ of μ: ~95% of data
Within 3σ of μ: ~99.7% of data

A point beyond 3σ is so rare that it is more likely to be a mistake, a special cause, or a genuinely exceptional case — hence "abnormal."

Watch out

The 3-sigma rule assumes the data follows a normal distribution. If the distribution is skewed or has heavy tails, this rule can misclassify normal points as abnormal. Always check the shape of your data first.

A Concrete Example

Suppose the mean height of Indian adult males is 165 cm with a standard deviation of 7 cm. A person who is 190 cm tall:

$z = \frac{190 - 165}{7} = \frac{25}{7} \approx 3.57$ …

Part (b)Concept understanding — Abnormality Definition

Abnormality Definition — First Principles

That is the core intuition behind abnormality in statistics: an observation that deviates so much from the rest of the data that it stands out as unusual.

The Precise Definition

\text{An observation } x \text{ is abnormal if } |x - \mu| > 3\sigma

Why 3-Sigma? The Intuition

The number 3 is not arbitrary. In a normal distribution:

Within 1σ of μ: ~68% of data
Within 2σ of μ: ~95% of data
Within 3σ of μ: ~99.7% of data

A point beyond 3σ is so rare that it is more likely to be a mistake, a special cause, or a genuinely exceptional case — hence "abnormal."

Watch out

A Concrete Example

Suppose the mean height of Indian adult males is 165 cm with a standard deviation of 7 cm. A person who is 190 cm tall:

$z = \frac{190 - 165}{7} = \frac{25}{7} \approx 3.57$ …

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Ravi's abnormal behaviour can be understood through the biological, psychodynamic, behavioural, cognitive, humanistic-existential and socio-cultural models and the diathesis-stress model.
Views of disorders evolved from biological and psychological origins, through the demonological Middle Ages and the humane Renaissance/Enlightenment reforms, to the modern bio-psycho-social approach.

Part (a)

As a psychology student, one would explain Ravi's extreme social withdrawal and erratic mood swings by applying the several models / approaches / factors used to understand abnormal behaviour (any four explained):

Biological (medical) factors. Abnormal behaviour has physical or organic roots — genetic predisposition, biochemical imbalances (e.g., abnormal neurotransmitter activity), hormonal factors, or structural/functional problems of the brain and nervous system.
Psychodynamic model. Following Freud, disorders arise from unresolved unconscious conflicts, unmet instinctual demands and unhappy early-childhood experiences that create anxiety.
Behavioural model. Abnormal behaviour is learned in the same way as normal behaviour — through classical conditioning, operant conditioning and observational learning — and can therefore be unlearned.
Cognitive model. Disorders result from faulty, irrational or distorted thoughts and beliefs (dysfunctional cognitions) about oneself and the world.
Humanistic-existential model. Abnormality reflects blocked personal growth, an unmet need for self-actualisation, or a loss of meaning and responsibility in living.
Socio-cultural model. Family systems, social conditions (poverty, discrimination), and cultural expectations contribute to disorder.
Diathesis-stress model. A person carries a diathesis (a biological or psychological predisposition/vulnerability); when combined with significant stress, the disorder is triggered. This integrative model shows how the above factors combine. …

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Q.(a) Ravi has been showing signs of extreme social withdrawal and erratic mood swings. As a psychology student, how would you apply different approaches/models/factors to understand and explain any abnormal behaviour?

Part (a)

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