Defining Normal vs Abnormal Behaviour
1. Why It’s Difficult to Define
There’s no single definition of “abnormal.”
Psychologists look at several criteria together — because what is
considered “normal” depends on:
Context (situation, culture, age)
Degree (how extreme the behaviour is)
Duration (how long it persists)
Impact (how it affects functioning)
2. Three Main Diagnostic Criteria
Criterion Definition Example / Application
Feeling sad occasionally =
Behaviour that falls
Statistical normal. Continuous severe
outside what is typical
Deviance sadness = statistically rare → may
or common.
indicate depression.
Behaviour that
An adult avoiding all social
Maladaptivene interferes with daily
contact can’t maintain
ss life or endangers
relationships → maladaptive.
self/others.
Behaviour that causes Panic attacks that cause severe
Personal
personal suffering or distress, even if they don’t harm
Distress
anguish. others.
✅ Note: No single criterion alone defines a disorder- a
combination usually indicates abnormality.
3. Social Norms & Age Norms
Social norms: Expected ways of behaving within a society or
culture.
What’s normal in one culture might be abnormal in another.
Example: Hearing voices might be spiritual in one culture but a
psychotic symptom in another.
Age norms: Expected behaviour at certain developmental stages.
A toddler’s tantrum = normal.
A 20-year-old’s tantrum = concerning.
Therefore, psychologists always consider context + age before
deciding if behaviour is abnormal.
, 4. Developmental Issues
Understanding abnormal behaviour requires knowing how development
should progress:
Continuity vs. Discontinuity → Is behaviour part of a normal
developmental phase or a sharp deviation?
Nature vs. Nurture → Are problems inherited (biological) or learned
(environmental)?
Example:
A 4-year-old with short attention span = developmentally typical.
A 10-year-old with severe attention deficits = may suggest ADHD.
5. Diathesis–Stress Model of Psychopathology
Key concept often tested!
Definition:
Psychological disorders result from the interaction between a
predisposition (diathesis) and environmental stress.
Compone
Explanation Example (Depression)
nt
Biological vulnerability or
The 5-HTTLPR gene linked
Diathesis predisposition (e.g., genes, brain
to difficulty handling stress.
chemistry)
Environmental trigger (e.g., Breakup, family conflict,
Stress
trauma, loss, conflict) chronic stress.
Interactio Stress activates the predisposition Adolescent with gene +
n → symptoms emerge stress = depression onset.
Takeaway:
Neither genes nor environment alone cause disorders- it’s their
interaction over time that determines outcomes.
6. Gene–Environment Interaction
Environment can activate or silence genetic vulnerabilities.
The relationship between stress and disorder is reciprocal → stress
worsens the disorder, the disorder increases stress.
Example:
A teen genetically prone to anxiety may experience bullying → anxiety
increases → withdrawal leads to more stress → cycle continues.
1. Why It’s Difficult to Define
There’s no single definition of “abnormal.”
Psychologists look at several criteria together — because what is
considered “normal” depends on:
Context (situation, culture, age)
Degree (how extreme the behaviour is)
Duration (how long it persists)
Impact (how it affects functioning)
2. Three Main Diagnostic Criteria
Criterion Definition Example / Application
Feeling sad occasionally =
Behaviour that falls
Statistical normal. Continuous severe
outside what is typical
Deviance sadness = statistically rare → may
or common.
indicate depression.
Behaviour that
An adult avoiding all social
Maladaptivene interferes with daily
contact can’t maintain
ss life or endangers
relationships → maladaptive.
self/others.
Behaviour that causes Panic attacks that cause severe
Personal
personal suffering or distress, even if they don’t harm
Distress
anguish. others.
✅ Note: No single criterion alone defines a disorder- a
combination usually indicates abnormality.
3. Social Norms & Age Norms
Social norms: Expected ways of behaving within a society or
culture.
What’s normal in one culture might be abnormal in another.
Example: Hearing voices might be spiritual in one culture but a
psychotic symptom in another.
Age norms: Expected behaviour at certain developmental stages.
A toddler’s tantrum = normal.
A 20-year-old’s tantrum = concerning.
Therefore, psychologists always consider context + age before
deciding if behaviour is abnormal.
, 4. Developmental Issues
Understanding abnormal behaviour requires knowing how development
should progress:
Continuity vs. Discontinuity → Is behaviour part of a normal
developmental phase or a sharp deviation?
Nature vs. Nurture → Are problems inherited (biological) or learned
(environmental)?
Example:
A 4-year-old with short attention span = developmentally typical.
A 10-year-old with severe attention deficits = may suggest ADHD.
5. Diathesis–Stress Model of Psychopathology
Key concept often tested!
Definition:
Psychological disorders result from the interaction between a
predisposition (diathesis) and environmental stress.
Compone
Explanation Example (Depression)
nt
Biological vulnerability or
The 5-HTTLPR gene linked
Diathesis predisposition (e.g., genes, brain
to difficulty handling stress.
chemistry)
Environmental trigger (e.g., Breakup, family conflict,
Stress
trauma, loss, conflict) chronic stress.
Interactio Stress activates the predisposition Adolescent with gene +
n → symptoms emerge stress = depression onset.
Takeaway:
Neither genes nor environment alone cause disorders- it’s their
interaction over time that determines outcomes.
6. Gene–Environment Interaction
Environment can activate or silence genetic vulnerabilities.
The relationship between stress and disorder is reciprocal → stress
worsens the disorder, the disorder increases stress.
Example:
A teen genetically prone to anxiety may experience bullying → anxiety
increases → withdrawal leads to more stress → cycle continues.
