INTRODUCTION TO PSYCHOLOGY

Foundations and Historical Origins of Psychology

Psychology is formally defined as the scientific study of behavior, which refers to observable actions, and mental processes, including internal thoughts and feelings. The etymology of the term originates from the Greek words psyche, which means mind, and logos, meaning the study of. Psychological study distinguishes between overt behavior, which is external and observable, and covert behavior, which is internal. The discipline is characterized by systematic and objective approaches to understanding cognitive function. Historically, the roots of psychology are found in Greek philosophy. Socrates proposed the existence of two realms: the Physical realm, which is changeable, and the Ideal realm, which is unchanging and relates to the soul. He is well-known for the Socratic Method, which involves questioning and introspection. Plato, a student of Socrates, believed the mind consisted of three distinct parts: appetite, which drives desires; passion, representing emotions; and reason, which handles logic. Aristotle identified three types of souls: the vegetative soul related to growth, the sentient soul involving emotions and desires, and the rational soul representing the intellect.

Moving into the modern era, René Descartes introduced the concept of mind–body dualism, famous for the dictum "I think, therefore I am," suggesting that mental acts directly affect physical acts. Wilhelm Wundt is recognized as the Father of Psychology for establishing the first psychological laboratory in Leipzig in the year $1879$, where he utilized objective introspection. Edward Titchener founded Structuralism, which sought to analyze the structure of the mind by breaking it down into sensations and emotions. William James established Functionalism, focusing on the purpose of mental processes and how they help humans adapt, a view heavily influenced by Charles Darwin. Other major schools of thought include Gestalt Psychology, which posits that the whole of a perception is greater than the sum of its parts, and Sigmund Freud’s Psychoanalysis, which emphasizes the role of unconscious drives and early childhood experiences. Finally, Behaviorism, championed by Ivan Pavlov and John B. Watson, argues that behavior is learned through conditioning and that psychology should only study observable actions.

Modern Psychological Perspectives

The psychodynamic perspective evolved from Freud’s work to include the unconscious mind and early life experiences, while also incorporating the concepts of self and interpersonal relationships; key figures include Sigmund Freud, Carl Jung, and Alfred Adler. The behavioral perspective focuses on how learning occurs through conditioning and reinforcement, as seen in the work of Ivan Pavlov, John B. Watson, and B. F. Skinner. The humanistic perspective emphasizes free will and the drive toward self-actualization, led by thinkers like Abraham Maslow and Carl Rogers. Cognitive psychology focuses on internal mental processes such as thinking, memory, and problem-solving, with major contributions from Jean Piaget and Noam Chomsky.

The sociocultural perspective examines the influence that society and culture have on individual behavior, as studied by Lev Vygotsky, Albert Bandura, and Philip Zimbardo. The biopsychological perspective looks for biological causes for behavior, such as the brain, hormones, and genetics. Additionally, the evolutionary perspective focuses on universal mental traits that humans have developed for survival and adaptation, with key researchers including David Buss and Richard Dawkins.

Careers and Research Methodology in Psychology

There are several career paths within the field. A Psychologist typically holds a degree and has undergone specific training in psychology. In contrast, a Psychiatrist is a medical doctor who specializes in treating mental disorders. In the Philippines (PH), an RPsy refers to a Licensed Psychologist, while an RPm refers to a Licensed Psychometrician. The academic pathway generally follows a progression from a Bachelor of Arts (BA) or Bachelor of Science (BS) in Psychology to a Master of Arts (MA) and eventually a Doctor of Philosophy (PhD). The primary goals of psychological research are to describe, explain, predict, and control behavior. Research is categorized into basic research, which aims to gain new knowledge, and applied research, which seeks to solve practical problems.

Psychologists use the scientific approach, which follows a sequence of steps: forming a question, developing a hypothesis, testing the hypothesis, drawing a conclusion, and reporting the results. Descriptive research methods include naturalistic or laboratory observation, case studies, and surveys. Researchers must be cautious of the observer effect and observer bias. Correlational research examines the strength and direction of relationships between variables, which can be positive ($+$), negative ($-$), or non-existent. In experimental research, the Independent Variable (IV) is manipulated while the Dependent Variable (DV) is measured. Participants are divided into an Experimental Group, which receives the IV, and a Control Group, which may receive a placebo. Random assignment ensures every participant has an equal chance of being in either group. Researchers must account for the Placebo Effect, where a participant's belief affects the outcome, and the Experimenter Effect, which is bias introduced by the researcher. Control measures include Single-Blind studies, where participants are unaware of their group, and Double-Blind studies, where both participants and researchers are unaware. Critical thinking in psychology involves recognizing that there are few absolute truths, evaluating the quality of evidence, understanding that authority does not equal truth, and maintaining an open mind.

Sampling Methods in Research

Selecting participants involves various sampling methods. Simple Random Sampling gives every member of a population an equal chance of selection. Systematic Sampling involves selecting participants based on a set interval, such as every $5^{th}$ person. Stratified Sampling divides the population into categories and samples from each. Cluster Sampling involves selecting entire groups or clusters. Convenience Sampling relies on choosing the easiest-to-reach participants. Purposive Sampling involves selecting participants for a specific, pre-defined purpose. Quota Sampling requires recruiting participants until a set number per category is reached. Finally, Snowball Sampling involves current participants recruiting other participants for the study.

Principles of Developmental Psychology

Developmental psychology is the scientific study of the changes that occur in people from the moment of conception until death. Scientists study development using several designs: Longitudinal studies follow the same group of people over many years; Cross-sectional studies compare different age groups at one point in time; Cross-sequential studies combine longitudinal and cross-sectional methods; and Retrospective studies ask individuals to recall past events. A central debate in this field is Nature versus Nurture, where nature refers to inherited traits and genes, and nurture refers to environmental influences like family and culture.

Developmental theories often categorize growth into biological (body and brain), evolutionary (survival), cognitive (memory and thought), humanistic (free will), psychodynamic (unconscious), behaviorist (rewards and punishments), and sociocultural (relationships) domains. Genetics plays a fundamental role, centered on DNA, the molecule carrying life’s instructions. A gene is a specific section of DNA, and chromosomes are rod-shaped bundles of genes. Humans possess $46$ chromosomes, with $23$ inherited from each parent. Dominant genes are expressed more strongly than recessive ones.

Prenatal Development and Early Childhood

Prenatal development occurs in three stages: the Germinal stage ($0$ to $2$ weeks) involving cell division; the Embryonic stage ($3$ to $8$ weeks) where organs form and brain regions like the midbrain, hindbrain, and forebrain appear; and the Fetal stage ($9$ weeks to birth) where the baby grows in size and strength. A useful mnemonic for these stages is “GEF → Grow Every Fetus.” During this time, the Critical Period is a window when environmental influences can cause significant harm. A Teratogen is any harmful substance, such as alcohol or drugs, that can interfere with development. In infancy and childhood, the brain grows rapidly, and synaptic pruning removes unnecessary neurons. Sensory capabilities such as touch, smell, taste, and hearing are well-developed at birth, while vision remains the weakest sense.

Psychosocial and Cognitive Development Theories

Erik Erikson proposed eight psychosocial stages of development: Infancy ($0$ to $1$ year) - Trust vs. Mistrust; Early Childhood ($1$ to $3$ years) - Autonomy vs. Shame; Play Age ($3$ to $6$ years) - Initiative vs. Guilt; School Age ($6$ to $12$ years) - Industry vs. Inferiority; Adolescence ($12$ to $19$ years) - Identity vs. Role Confusion; Early Adulthood ($20$ to $25$ years) - Intimacy vs. Isolation; Adulthood ($26$ to $64$ years) - Generativity vs. Stagnation; and Old Age ($65$ years and older) - Integrity vs. Despair.

Jean Piaget outlined four stages of cognitive development: Sensorimotor ($0$ to $2$ years), where children learn through senses and movement; Preoperational ($2$ to $7$ years), involving language and imagination but remaining egocentric; Concrete Operational ($7$ to $12$ years), where logical thinking about real objects begins; and Formal Operational ($12$ years and older), characterized by abstract thought. Attachment styles between children and parents are categorized as Secure (trusting), Ambivalent (clingy/mixed), Avoidant (distant), and Disordered (afraid). These can be remembered with the mnemonic ‘SAAD kids.’

Adolescence, Adulthood, and Aging

Adolescence occurs from age $13$ into the $20s$ and is marked by biological puberty and cognitive changes like abstract thought, the imaginary audience (feeling watched by everyone), and the personal fable (feeling unique and special). Lawrence Kohlberg identified stages of moral development: Preconventional (based on consequences), Conventional (following rules), and Postconventional (based on personal ethics). Adulthood is split into early adulthood ($20s$ to $30s$) focusing on career and family, and middle adulthood ($40s$ to $50s$) involving life reflection. Later years involve retirement and health changes. Theories of aging include the Cellular Clock theory (limited cell division), Wear and Tear theory (body wearing out), Free Radical theory (damage by unstable molecules), and Activity Theory (active living leads to healthy aging). The mnemonic ‘CWFA → Cells Wear Free Activity’ summarizes these.

Parenting styles significantly impact development and include Permissive (too indulgent), Neglectful (uninvolved), Authoritarian (too strict), and Authoritative (balanced and ideal). The process of death and dying is often described using Elisabeth Kbler-Ross’s stages: Denial, Anger, Bargaining, Depression, and Acceptance, remembered by the mnemonic ‘DABDA → Don’t Ask Big Dark Answers.’

Biopsychology and Neural Communication

Biopsychology studies how the body and brain affect thoughts and feelings. Neurons are the brain's primary messengers. A neuron consists of Dendrites (receivers), the Soma (cell body), the Axon (transmitter), and Axon Terminals (endpoints that communicate with other cells). The Synapse is the gap between neurons where messages jump. This structure can be remembered with the mnemonic: “Do Smart Apes Always Study?” Neurons operate on an all-or-none principle, similar to a light switch. The process of an action potential follows specific steps: the neuron is at a resting potential of $-70\,mV$; it must hit a threshold of $-55\,mV$ to fire; Depolarization occurs as sodium ($Na+$) rushes in, making the inside positive; Repolarization occurs as potassium ($K+$) leaves, returning it to a negative state; Hyperpolarization makes it too negative, requiring a rest; finally, the sodium-potassium pump resets the balance ($3\,Na+$ out and $2\,K+$ in). The mnemonic for this is “Ready To Do Real Hard Resets.” The period before a neuron can fire again is the refractory period.

Neurotransmitters are chemicals that travel across the synapse to deliver messages that are either Excitatory (inducing firing) or Inhibitory (stopping firing). An Agonist is a substance that mimics or boosts a neurotransmitter, while an Antagonist blocks it. These chemicals are stored in synaptic vesicles and bind to specific receptor sites on the receiving cell. After the message is delivered, neurotransmitters are either reused through reuptake or drift away through diffusion. A simple mnemonic is ‘Agonist Adds, Antagonist Anti.’

The Nervous and Endocrine Systems

The Nervous System is divided into the Central Nervous System (CNS), consisting of the brain and spinal cord, and the Peripheral Nervous System (PNS). The brain exhibits neuroplasticity, allowing it to rewire after trauma, and neurogenesis, the birth of new neurons in the hippocampus. The PNS includes the Somatic System for voluntary actions and the Autonomic System for automatic actions. The Autonomic System has two branches: the Sympathetic (Fight or Flight) and the Parasympathetic (Rest and Digest). Sensory neurons are Afferent (to the brain), and motor neurons are Efferent (from the brain), remembered by the mnemonic ‘SAME.’

The brain contains several key parts: the Cortex (outer layer for thinking), the Corpus Callosum (bridge between hemispheres), the Cerebrum (upper brain), and four lobes symbolized by ‘FOPT’: Frontal (decisions and Broca’s area for speech production), Occipital (vision), Parietal (touch and position), and Temporal (hearing and Wernicke’s area for language understanding). Other structures include the Cerebellum (balance) and the Limbic System, containing the Amygdala (emotion) and Hippocampus (memory). Mirror neurons fire when observing or performing actions.

The Endocrine System uses hormones secreted into the blood. Major glands include the Pituitary (master gland), Pineal (melatonin for sleep), Thyroid (metabolism), Pancreas (insulin and blood sugar), Gonads (sex hormones), and Adrenal (stress/adrenaline). This can be remembered as “Pretty People Think Pink Goo Awesome” or ‘PiPiT-Pa-