Class 11 Psychology Notes Chapter 3 (The Bases of Human Behaviour) – Introduction to Pshycology Book

Alright class, let's delve into Chapter 3: The Bases of Human Behaviour. This chapter is crucial as it lays the foundation for understanding why we behave the way we do, looking at both our biological makeup and the cultural context we live in. For your government exam preparation, focus on the key terms, structures, functions, and concepts.

Chapter 3: The Bases of Human Behaviour - Detailed Notes

I. Introduction: The Interplay of Nature and Nurture

• Human behaviour is complex and results from an intricate interplay between our biological inheritance (nature) and our experiences within our environment and culture (nurture).
• This chapter explores these biological and socio-cultural foundations.

II. Evolutionary Perspective

• Core Idea: Based on Charles Darwin's theory of evolution by Natural Selection.
• Natural Selection: Organisms better adapted to their environment tend to survive and produce more offspring. Over generations, characteristics that enhance survival and reproduction become more common.
• Relevance to Behaviour: Many human behaviours (e.g., attachment, mate selection preferences, certain emotional responses like fear of snakes/spiders) may have evolutionary roots because they conferred survival or reproductive advantages to our ancestors.
• Key Point: Evolution equips us with predispositions, not hardwired behaviours. Environment and culture significantly shape how these predispositions are expressed.

III. Biological Basis of Behaviour

A. Neurons: The Building Blocks

• Definition: Neurons (nerve cells) are the basic units of the nervous system, specialized for receiving, processing, and transmitting information.
• Structure:
  • Soma (Cell Body): Contains the nucleus; maintains the life of the cell.
  • Dendrites: Branch-like structures that receive messages from other neurons.
  • Axon: Long, tube-like structure that transmits messages away from the soma towards other neurons, muscles, or glands.
  • Myelin Sheath: Fatty layer insulating many axons; speeds up neural transmission.
  • Axon Terminal (Terminal Buttons): Endings of the axon that release neurotransmitters.
  • Synapse: The microscopic gap between the axon terminal of one neuron and the dendrite/soma of another, across which communication occurs.
• Neural Impulse (Action Potential):
  • An electrical signal travelling down the axon.
  • Operates on the All-or-None Principle: A neuron either fires completely or not at all; there's no partial firing. Strength of stimulus is coded by the frequency of firing, not the intensity of a single impulse.
• Neurotransmitters: Chemical messengers released into the synapse, binding to receptor sites on the next neuron, thus transmitting the signal. Examples include Acetylcholine, Dopamine, Serotonin, GABA. (Specific functions are less critical for this chapter's overview but know their general role).

B. The Nervous System: Organisation

• Central Nervous System (CNS): Command centre.

  • Brain: The core of the nervous system; responsible for complex behaviour and mental processes.
    • Hindbrain: Vital functions.
      • Medulla: Controls breathing, heart rate, blood pressure.
      • Pons: Involved in sleep, dreaming, arousal, coordinates movement between left/right body sides.
      • Cerebellum: Coordinates voluntary movement, balance, posture, and learned motor skills.
    • Midbrain: Relay station for sensory information; involved in arousal and attention (contains parts of the Reticular Activating System - RAS/ Reticular Formation).
    • Forebrain: Higher mental functions.
      • Thalamus: Relays sensory information (except smell) to the cerebral cortex.
      • Hypothalamus: Regulates basic biological needs (hunger, thirst, temperature), controls the pituitary gland, involved in emotion.
      • Limbic System: Involved in emotion, motivation, memory (includes hippocampus, amygdala, hypothalamus).
      • Cerebrum/Cerebral Cortex: Largest part; responsible for complex thought, perception, language. Divided into two hemispheres (left/right) connected by the Corpus Callosum. Each hemisphere has four lobes:
        • Frontal Lobe: Planning, decision-making, personality, voluntary movement (motor cortex), language production (Broca's area).
        • Parietal Lobe: Processing sensory information like touch, temperature, pain, pressure (somatosensory cortex); spatial awareness.
        • Temporal Lobe: Auditory processing (hearing), language comprehension (Wernicke's area), memory.
        • Occipital Lobe: Visual processing.
  • Spinal Cord: Connects the brain to the rest of the body; controls some reflex actions independently of the brain.

• Peripheral Nervous System (PNS): Nerves extending outside the CNS. Connects CNS to limbs and organs.

  • Somatic Nervous System: Controls voluntary muscles and transmits sensory information from the body to the CNS.
  • Autonomic Nervous System (ANS): Controls involuntary functions (heart rate, digestion, glands).
    • Sympathetic Division: Arouses the body for action ("Fight-or-Flight" response) - increases heart rate, diverts blood to muscles, releases adrenaline.
    • Parasympathetic Division: Calms the body, conserves energy ("Rest-and-Digest" response) - slows heart rate, stimulates digestion.

C. The Endocrine System: Chemical Communication

• Definition: A system of glands that secrete hormones (chemical messengers) directly into the bloodstream. Hormones travel slower than nerve impulses but have longer-lasting effects.
• Interaction: Works closely with the nervous system (especially the hypothalamus controlling the pituitary gland).
• Major Glands and Hormones:
  • Pituitary Gland: "Master gland"; controlled by the hypothalamus. Secretes hormones that regulate other glands and influence growth, blood pressure.
  • Thyroid Gland: Produces Thyroxin; regulates metabolism.
  • Adrenal Glands: Located above kidneys. Secrete Adrenaline (Epinephrine) and Noradrenaline (Norepinephrine) during stress/emergency (part of the fight-or-flight response). Also secrete corticosteroids.
  • Pancreas: Controls blood sugar levels via Insulin and Glucagon.
  • Gonads (Ovaries in females, Testes in males): Secrete sex hormones (Estrogen, Progesterone in females; Testosterone in males) responsible for sexual development, reproductive functions, and influencing behaviour.

IV. Heredity: Genes and Behaviour

• Heredity: Biological transmission of traits from parents to offspring through genes.
• Chromosomes: Thread-like structures in the nucleus of each cell, made of DNA. Humans have 23 pairs (46 total). 22 pairs are autosomes, 1 pair are sex chromosomes (XX for females, XY for males).
• DNA (Deoxyribonucleic Acid): Complex molecule containing genetic information.
• Genes: Segments of DNA; the functional units of heredity. They provide the blueprint for protein synthesis, which influences physical and psychological characteristics.
  • Genotype: An individual's actual genetic makeup.
  • Phenotype: An individual's observable characteristics (physical traits, behaviour), resulting from the interaction of genotype and environment.
  • Dominant vs. Recessive Genes: Dominant genes express their trait even if paired with a recessive gene. Recessive genes only express their trait if paired with another identical recessive gene.
• Behavioural Genetics: Studies the influence of genetic factors on behaviour.
  • Methods: Twin studies (comparing identical/monozygotic vs. fraternal/dizygotic twins), adoption studies (comparing adopted children to biological and adoptive parents).
  • Findings: Genes contribute to variations in intelligence, personality traits, and susceptibility to certain psychological disorders. Crucially, genes do not determine behaviour directly; they create predispositions that interact with environmental factors.

V. Cultural Basis: Socio-Cultural Shaping of Behaviour

• Culture: A shared system of beliefs, values, norms, customs, traditions, and artifacts transmitted across generations within a group. It provides a framework for understanding the world and guiding behaviour.
• Enculturation: The process of learning the values, norms, and behaviours of the culture one is born into. It happens largely implicitly through observation and participation.
• Socialization: A broader process through which individuals learn and internalize the rules, roles, skills, and values necessary to function within a given society or group. It's a lifelong process involving various agents of socialization:
  • Family (primary agent)
  • School
  • Peer groups
  • Media
  • Workplace
• Acculturation: The process of cultural and psychological change that occurs when individuals or groups from different cultures come into continuous first-hand contact.
  • Acculturative Stress: Stress resulting from the challenges of adapting to a new culture.
  • Strategies of Acculturation (John Berry's Model): Based on two questions: (1) Is maintaining one's original cultural identity important? (2) Is establishing relationships with the host society important?
    • Integration: Maintain original culture + Engage with host culture (Most adaptive).
    • Assimilation: Abandon original culture + Embrace host culture.
    • Separation: Maintain original culture + Avoid host culture.
    • Marginalization: Lose original culture + Fail to connect with host culture (Least adaptive; associated with most stress).

VI. Conclusion: The Biocultural Synthesis

• Behaviour is never just biological or just cultural. It emerges from the constant, dynamic interaction between genetic predispositions, physiological processes, personal experiences, and socio-cultural contexts. Understanding human behaviour requires considering all these levels of influence.

Multiple Choice Questions (MCQs)

1. Which part of the neuron is primarily responsible for receiving signals from other neurons?
   a) Axon
   b) Soma
   c) Dendrite
   d) Myelin Sheath

2. The principle stating that a neuron either fires at full strength or not at all is known as:
   a) The Synaptic Principle
   b) The All-or-None Principle
   c) The Threshold Principle
   d) The Refractory Principle

3. Which division of the nervous system is responsible for the "Fight-or-Flight" response?
   a) Central Nervous System
   b) Somatic Nervous System
   c) Parasympathetic Division
   d) Sympathetic Division

4. The gland often referred to as the "master gland" due to its influence on other endocrine glands is the:
   a) Thyroid Gland
   b) Adrenal Gland
   c) Pituitary Gland
   d) Pancreas

5. An individual's observable characteristics, resulting from the interaction of genes and environment, constitute their:
   a) Genotype
   b) Phenotype
   c) Chromosome
   d) Allele

6. The process of learning the norms, values, and behaviours of the culture one is born into is called:
   a) Socialization
   b) Acculturation
   c) Enculturation
   d) Assimilation

7. Which lobe of the cerebral cortex is primarily involved in processing visual information?
   a) Frontal Lobe
   b) Parietal Lobe
   c) Temporal Lobe
   d) Occipital Lobe

8. Which structure is crucial for coordinating voluntary movement, balance, and posture?
   a) Medulla
   b) Thalamus
   c) Cerebellum
   d) Hypothalamus

9. According to John Berry's model, which acculturation strategy involves maintaining one's original cultural identity while also engaging with the host culture?
   a) Assimilation
   b) Separation
   c) Marginalization
   d) Integration

10. Behavioural genetics often uses which method to study the relative influence of genes and environment?
    a) Case Studies
    b) Surveys
    c) Twin Studies
    d) Experimental Manipulation

Answer Key:

1. c) Dendrite
2. b) The All-or-None Principle
3. d) Sympathetic Division
4. c) Pituitary Gland
5. b) Phenotype
6. c) Enculturation
7. d) Occipital Lobe
8. c) Cerebellum
9. d) Integration
10. c) Twin Studies

Make sure you understand the definitions and functions clearly. Pay attention to the distinctions between related concepts like Enculturation and Socialization, or Genotype and Phenotype. Good luck with your preparation!