One of the fundamental questions in psychology is the nature vs. nurture debate: To what extent are our behaviors, traits, and abilities shaped by our genes (nature) versus our environment and experiences (nurture)? Modern psychology recognizes that it is not one or the other — it is the complex interaction between the two that makes us who we are.
Genetics and Behavior
Genes are segments of DNA that code for specific proteins, which influence the development and function of the body and brain. Humans share approximately 99.9% of their DNA with one another; the remaining 0.1% accounts for individual differences.
Chromosomes: Humans have 23 pairs of chromosomes (46 total). The 23rd pair determines biological sex (XX = female, XY = male).
Genotype vs. Phenotype: The genotype is the set of genes an organism carries; the phenotype is the observable expression of those genes (influenced by environment).
Behavioral Genetics: How We Study Nature vs. Nurture
Twin Studies: Identical (monozygotic) twins share 100% of their DNA; fraternal (dizygotic) twins share approximately 50%. By comparing the similarity of traits in identical vs. fraternal twins, researchers can estimate how much genetics contributes to a trait.
Adoption Studies: Compare adopted children with both their biological parents (genetic influence) and adoptive parents (environmental influence) to tease apart nature and nurture.
Heritability: A statistical estimate of how much of the variation in a trait within a population can be attributed to genetic differences. For example, a heritability of 0.70 for intelligence means 70% of the variation in intelligence within that group is due to genetic factors — not that 70% of any one person's intelligence is genetic.
DNA double helix — the molecule that carries our genetic instructions (Wikimedia Commons, Public Domain)
Epigenetics
Epigenetics is the study of how the environment can alter gene expression without changing the underlying DNA sequence. Environmental factors like stress, diet, toxins, and early life experiences can turn genes "on" or "off" through chemical modifications (such as DNA methylation). These changes can sometimes be passed across generations. This is a powerful example of the nature–nurture interaction: your environment literally shapes how your genes operate.
Key Takeaway: Genes set the range of possibilities for a trait, and the environment determines where within that range an individual falls. Nature and nurture always work together.
⚡ 1.2 Overview of the Nervous System
The nervous system is the body's electrochemical communication network. It is responsible for receiving sensory input, processing information, and directing motor output. It is divided into two major parts:
Central Nervous System (CNS)
The CNS consists of the brain and the spinal cord. It is the body's command center, responsible for processing and interpreting all incoming information and sending out response signals.
Brain: The most complex organ in the body; processes sensory information, controls movement, regulates emotions, enables thinking and memory.
Spinal Cord: A long bundle of neural fibers running from the brainstem down the vertebral column. It relays messages between the brain and the rest of the body and coordinates simple reflexes (reflex arcs bypass the brain for faster response).
Peripheral Nervous System (PNS)
The PNS includes all nerves outside the brain and spinal cord. It connects the CNS to the rest of the body and is subdivided into:
Somatic Nervous System: Controls voluntary movements. It carries sensory information to the CNS and motor commands from the CNS to skeletal muscles. Example: deciding to raise your hand in class.
Autonomic Nervous System (ANS): Controls involuntary functions (heart rate, digestion, breathing). The ANS is further divided into:
Sympathetic Nervous System: Activates the "fight-or-flight" response. Increases heart rate, dilates pupils, inhibits digestion, releases adrenaline — preparing the body to face or escape a threat.
Parasympathetic Nervous System: Activates the "rest-and-digest" response. Slows heart rate, constricts pupils, stimulates digestion — calming the body after a stressful event. (Memory tip: Para = parachute = slows you down.)
The Endocrine System
Though not technically part of the nervous system, the endocrine system works closely with it. Glands (such as the pituitary, thyroid, adrenal glands, and gonads) secrete hormones into the bloodstream. Hormones are chemical messengers that regulate growth, metabolism, mood, and reproduction. The hypothalamus serves as the link between the nervous system and the endocrine system by directing the pituitary gland (the "master gland").
The human nervous system: Central (brain & spinal cord) and Peripheral divisions (Wikimedia Commons, Public Domain)
Key Takeaway: The nervous system hierarchy: CNS (brain + spinal cord) and PNS (somatic + autonomic). The autonomic system's sympathetic and parasympathetic divisions work in opposition to maintain balance (homeostasis).
🔬 1.3 The Neuron and Neural Firing
Neurons are the building blocks of the nervous system. The human brain contains roughly 86 billion neurons, each forming thousands of connections. Understanding how neurons communicate is foundational to understanding all behavior.
Structure of a Neuron
Dendrites: Branch-like extensions that receive signals from other neurons or sensory receptors and carry them toward the cell body.
Cell Body (Soma): Contains the nucleus and keeps the neuron alive. Integrates incoming signals and determines whether to pass the signal along.
Axon: A long, cable-like fiber that carries the electrical impulse (action potential) away from the cell body toward the axon terminals.
Myelin Sheath: A fatty insulating layer that wraps around the axon in segments. Speeds up neural transmission and protects the axon. Gaps between myelin segments are called Nodes of Ranvier, where the signal "jumps" from node to node (saltatory conduction). Deterioration of myelin is associated with diseases like multiple sclerosis (MS).
Axon Terminals (Terminal Buttons): Tiny knobs at the end of the axon that release neurotransmitters into the synaptic gap.
How Neurons Fire: The Action Potential
Resting Potential (~−70 mV): The neuron is at rest, with the inside of the cell more negatively charged than the outside (due to ion distribution).
Threshold: When a neuron receives enough stimulation to reach the threshold of excitation (~−55 mV), an action potential is triggered.
Action Potential (All-or-Nothing): Sodium (Na+) channels open and positively charged ions rush in, depolarizing the neuron. This electrical signal travels down the axon. The neuron either fires completely or not at all — there is no "partial" firing.
Repolarization: Potassium (K+) channels open and positive ions flow out, restoring the negative charge inside the neuron.
Refractory Period: A brief rest period during which the neuron cannot fire again. This ensures signals travel in one direction.
Synaptic Transmission
When the action potential reaches the axon terminals, it triggers the release of neurotransmitters into the synaptic cleft (the tiny gap between two neurons). These chemical messengers bind to receptor sites on the dendrites of the next neuron, either exciting or inhibiting it. Afterward, neurotransmitters are cleared via reuptake (reabsorbed by the sending neuron) or enzymatic breakdown.
A complete labeled neuron showing dendrites, cell body, axon, myelin sheath, and axon terminals (Wikimedia Commons, CC BY-SA 3.0)
Key Neurotransmitters
Neurotransmitter
Function
Associated Disorders (If Imbalanced)
Acetylcholine (ACh)
Muscle contraction, memory, learning
Low levels → Alzheimer's disease
Dopamine
Movement, motivation, reward, pleasure
Low → Parkinson's disease; Excess → linked to schizophrenia
Serotonin
Mood regulation, sleep, appetite
Low levels → depression, anxiety
Norepinephrine
Alertness, arousal, fight-or-flight response
Imbalance → depression, ADHD
GABA (Gamma-Aminobutyric Acid)
Major inhibitory neurotransmitter; calms neural activity
Low levels → anxiety, seizures, epilepsy
Glutamate
Major excitatory neurotransmitter; learning, memory
Excess → overstimulation, migraines, seizures
Endorphins
Natural pain relief, feelings of pleasure
Low levels → increased pain sensitivity
Glial Cells (Supporting Cast)
Neurons aren't alone in the nervous system. Glial cells (approximately 85 billion in the brain) support neurons by providing nutrients, insulating axons (forming myelin), removing waste, and even modulating neural communication. Types include astrocytes, oligodendrocytes (create myelin in the CNS), and Schwann cells (create myelin in the PNS).
Key Takeaway: Neural communication is electrochemical: electrical within the neuron (action potential) and chemical between neurons (neurotransmitters across the synapse). The action potential is "all-or-nothing."
🧠 1.4 The Brain
The brain is the most complex organ in the human body and the command center for all behavior, thought, and emotion. Understanding its structures and their functions is a major focus of AP Psychology.
The Brainstem (Basic Survival)
Located at the base of the brain, the brainstem controls essential life functions:
Medulla Oblongata: Controls heartbeat, breathing, and blood pressure. Damage here is often fatal.
Pons: Involved in sleep regulation, coordination of movement, and relaying information between the cerebellum and cerebral cortex.
Reticular Formation: A network of neurons running through the brainstem that controls arousal and attention. It filters incoming sensory information and determines what you consciously notice.
The Cerebellum ("Little Brain")
Located at the back of the brain, the cerebellum coordinates voluntary movement, balance, and motor learning. It also plays a role in timing and some cognitive processes. Damage leads to clumsy, uncoordinated movement.
The Thalamus
The brain's sensory relay station. Nearly all sensory information (except smell) passes through the thalamus before reaching the cerebral cortex. Think of it as the brain's switchboard operator.
The Limbic System (Emotion & Memory)
Amygdala: Processes emotions, especially fear and aggression. It is essential for forming emotional memories and the fight-or-flight response.
Hippocampus: Critical for forming new explicit memories (facts and events). Damage to the hippocampus results in the inability to form new long-term memories (as seen in the famous case of patient H.M.).
Hypothalamus: Regulates basic drives including hunger, thirst, body temperature, and sexual behavior. It directs the endocrine system via the pituitary gland and is involved in the reward circuit.
The major lobes and regions of the human brain (Wikimedia Commons, CC BY-SA 4.0)
The Cerebral Cortex (Higher Thinking)
The cerebral cortex is the thin, wrinkled outer layer of the brain responsible for higher-order functions like thinking, planning, language, and consciousness. It is divided into two hemispheres, each with four lobes:
Motor Cortex: Controls voluntary movements (along the rear edge of the frontal lobe)
Broca's Area: Controls speech production (usually left hemisphere). Damage → Broca's aphasia (can understand language but struggles to speak fluently)
The famous case of Phineas Gage, who survived an iron rod through his frontal lobe, demonstrated this area's role in personality and impulse control
Parietal Lobe (top of the brain, behind frontal)
Somatosensory Cortex: Processes touch, pressure, temperature, and pain sensations from the body
Spatial reasoning and navigation
Integrating sensory information from different modalities
Temporal Lobe (sides of the brain, near ears)
Auditory Cortex: Processes sound and hearing
Wernicke's Area: Responsible for language comprehension (usually left hemisphere). Damage → Wernicke's aphasia (can speak fluently but speech is meaningless)
Also involved in memory and face recognition
Occipital Lobe (back of the brain)
Visual Cortex: Processes visual information from the eyes
Damage can cause blindness even if the eyes are perfectly healthy (cortical blindness)
Brain Lateralization & Split-Brain Research
The two hemispheres are connected by the corpus callosum, a thick band of nerve fibers that allows communication between them. Research by Roger Sperry and Michael Gazzaniga on split-brain patients (whose corpus callosum was severed) revealed that:
The left hemisphere is typically dominant for language, logic, and analytical processing.
The right hemisphere excels at spatial tasks, face recognition, and processing emotional content.
In everyday life, both hemispheres work together seamlessly via the corpus callosum.
Neuroplasticity
The brain has a remarkable ability to reorganize and form new neural connections throughout life, especially in response to learning, experience, or injury. This is called neuroplasticity. Younger brains are more plastic, but even adult brains can adapt (e.g., a stroke patient may recover lost function as other brain areas take over).
Brain Research Techniques
Technique
What It Measures
Key Details
EEG
Electrical activity
Electrodes on scalp; great temporal resolution; used in sleep research
CT Scan
Brain structure
X-ray images; shows damage/tumors
MRI
Brain structure
Magnetic fields; detailed images of soft tissue
fMRI
Brain activity
Measures blood flow/oxygen use; shows which areas are active during tasks
Key Takeaway: Know the major brain structures and their functions, the four cortical lobes, Broca's vs. Wernicke's areas, split-brain research, and the concept of neuroplasticity.
💤 1.5 Sleep
Sleep is a naturally recurring altered state of consciousness that is essential for physical restoration, memory consolidation, and emotional regulation. The AP Psychology exam expects you to understand sleep stages, sleep disorders, and theories of why we sleep.
Circadian Rhythms
The body's internal 24-hour biological clock, regulated by the suprachiasmatic nucleus (SCN) in the hypothalamus. The SCN responds to light cues from the eyes and signals the pineal gland to release melatonin, a hormone that promotes drowsiness. Circadian rhythms regulate the sleep-wake cycle, body temperature, and hormone release.
Stages of Sleep
Sleep is divided into NREM (Non-Rapid Eye Movement) and REM (Rapid Eye Movement) stages, cycling approximately every 90 minutes:
NREM Stage 1 (N1): Light sleep. The transition from wakefulness to sleep, lasting a few minutes. You may experience hypnagogic hallucinations (vivid sensory experiences) or hypnic jerks (sudden muscle twitches). Brain waves shift from alpha to theta waves.
NREM Stage 2 (N2): Slightly deeper sleep. Body temperature drops and heart rate slows. Characterized by sleep spindles (bursts of rapid brain activity) and K-complexes. This stage comprises the largest portion of total sleep time.
NREM Stage 3 (N3 — Slow-Wave Sleep): The deepest stage of sleep. Dominated by delta waves (large, slow brain waves). This is when physical restoration occurs — growth hormone is released, tissues repair, and the immune system strengthens. It is hardest to wake someone from this stage. Sleepwalking and night terrors typically occur here.
REM Sleep: The brain becomes highly active (similar to wakefulness), eyes dart rapidly, and most vivid dreaming occurs. The body experiences muscle atonia (temporary paralysis) to prevent acting out dreams. REM is critical for memory consolidation (especially procedural and emotional memories) and emotional processing. REM periods get longer as the night progresses.
A typical sleep hypnogram showing cycles through NREM and REM stages across a night (Wikimedia Commons, Public Domain)
Theories of Why We Sleep
Restoration Theory: Sleep allows the body and brain to repair, restore, and recover from daily wear.
Information Consolidation Theory: Sleep helps process and consolidate memories from the day.
Evolutionary/Adaptive Theory: Sleep evolved to keep organisms safe during vulnerable times (e.g., darkness).
Brain Plasticity Theory: Sleep is necessary for neural development and reorganization, especially in children.
Sleep Disorders
Disorder
Description
Insomnia
Persistent difficulty falling or staying asleep; the most common sleep disorder
Narcolepsy
Sudden, uncontrollable episodes of falling into REM sleep during waking hours; may cause cataplexy (sudden muscle weakness)
Sleep Apnea
Repeated pauses in breathing during sleep, often due to airway obstruction; leads to poor sleep quality and daytime fatigue
Sleepwalking (Somnambulism)
Walking or performing complex behaviors during deep NREM (N3) sleep; more common in children
Night Terrors
Episodes of intense fear, screaming, or thrashing during deep NREM sleep; different from nightmares (which occur in REM)
REM Sleep Behavior Disorder
Muscle atonia fails during REM; individuals physically act out their dreams
Theories of Dreams
Freud's Wish Fulfillment: Dreams represent unconscious desires and thoughts. Manifest content = the literal storyline; latent content = the hidden symbolic meaning.
Activation-Synthesis Theory (Hobson & McCarley): Dreams are the brain's attempt to make sense of random neural activity during REM sleep.
Information-Processing Theory: Dreams help consolidate and process information and experiences from the day.
Cognitive Development Theory: Dreams reflect the dreamer's cognitive development and current concerns.
Key Takeaway: Know the sleep stages (especially the difference between NREM N3 and REM), circadian rhythms, major sleep disorders, and theories of dreaming.
👁️ 1.6 Sensation
Sensation is the process by which sensory receptors detect physical energy from the environment and convert it into neural signals that the brain can interpret. This process is called transduction. (Note: Perception — the interpretation of sensory information — is covered in Unit 2.)
General Principles of Sensation
Transduction: The conversion of one form of energy into another. In sensation, physical stimuli (light waves, sound waves, chemical molecules, pressure) are converted into electrochemical neural impulses.
Absolute Threshold: The minimum amount of stimulation needed to detect a stimulus 50% of the time. Example: the faintest sound you can hear in a quiet room.
Difference Threshold (Just Noticeable Difference / JND): The minimum change in a stimulus required to notice a difference. Related to Weber's Law: the JND is a constant proportion of the original stimulus (e.g., you'd notice a 1-lb difference on a 10-lb weight, but need a 10-lb difference on a 100-lb weight).
Signal Detection Theory: Our ability to detect a stimulus depends not just on its strength, but also on our psychological state (experience, motivation, expectations, fatigue). There is no single "absolute" threshold.
Sensory Adaptation: Decreased sensitivity to a constant, unchanging stimulus over time. Example: you stop noticing the feel of your clothes shortly after putting them on. This frees up attention for new or changing stimuli.
Vision
Light enters the eye through the cornea, passes through the pupil (controlled by the iris), is focused by the lens, and projected onto the retina.
The retina contains two types of photoreceptors:
Rods: Detect dim light and are responsible for peripheral and night vision. Very sensitive but do not detect color.
Cones: Detect color and fine detail. Concentrated in the fovea (center of the retina). Require more light to function.
Visual information travels via the optic nerve to the thalamus and then to the occipital lobe's visual cortex.
Cross-section of the human eye showing the cornea, lens, retina, and optic nerve (Wikimedia Commons, CC BY-SA 3.0)
Hearing (Audition)
Sound waves are collected by the outer ear (pinna), travel through the ear canal, and vibrate the eardrum (tympanic membrane).
These vibrations pass through three tiny bones in the middle ear — the hammer (malleus), anvil (incus), and stirrup (stapes) — which amplify the sound.
Vibrations reach the cochlea (snail-shaped, fluid-filled structure in the inner ear), where they stimulate hair cells that transduce sound into neural signals.
Signals travel via the auditory nerve to the thalamus and then to the temporal lobe's auditory cortex.
Other Senses
Touch: Receptors in the skin detect pressure, temperature, and pain. Processed in the somatosensory cortex of the parietal lobe.
Taste (Gustation): Taste buds on the tongue detect five basic tastes: sweet, sour, salty, bitter, and umami (savory).
Smell (Olfaction): Chemical molecules bind to receptors in the nasal cavity. Smell is the only sense that bypasses the thalamus, connecting directly to the olfactory bulb and then to limbic system structures (which is why smells can trigger powerful memories and emotions).
Vestibular Sense: Sense of balance and body position, detected by structures in the inner ear (semicircular canals).
Proprioception (Kinesthesia): Sense of body position and movement, based on feedback from muscles, tendons, and joints.
Key Takeaway: Sensation = detecting stimuli and transducing them into neural signals. Know absolute threshold, difference threshold (Weber's Law), signal detection theory, sensory adaptation, and the basics of how vision, hearing, and other senses work.
📚 Important Vocabulary
Term
Definition
Nature vs. Nurture
The longstanding debate about the relative contributions of genetics (nature) and environment (nurture) to behavior and mental processes.
Epigenetics
The study of how environmental factors can alter gene expression without changing the DNA sequence itself.
Heritability
A statistical measure of how much variation in a trait within a population is attributable to genetic differences.
Twin Studies
Research comparing identical and fraternal twins to estimate the relative influence of genetics and environment on traits.
Central Nervous System (CNS)
The brain and spinal cord; the body's central processing unit.
Peripheral Nervous System (PNS)
All nerves outside the CNS; connects the brain and spinal cord to the rest of the body.
Somatic Nervous System
The division of the PNS that controls voluntary muscle movements and carries sensory information to the CNS.
Autonomic Nervous System
The division of the PNS that controls involuntary functions like heart rate, digestion, and breathing.
Sympathetic Nervous System
The branch of the ANS that activates the body's "fight-or-flight" response in times of stress or danger.
Parasympathetic Nervous System
The branch of the ANS that calms the body and activates "rest-and-digest" functions.
Neuron
A nerve cell; the basic building block of the nervous system that transmits information via electrical and chemical signals.
Dendrite
Branching extensions of a neuron that receive incoming signals from other neurons.
Axon
The long fiber extending from the cell body of a neuron that carries electrical impulses (action potentials) away from the soma.
Myelin Sheath
A fatty insulating layer around the axon that speeds up neural transmission. Damage is linked to multiple sclerosis.
Action Potential
A brief electrical charge that travels down the axon of a neuron; an all-or-nothing event.
Synapse
The junction between two neurons, consisting of the axon terminal, synaptic cleft, and receptor sites on the receiving neuron.
Neurotransmitter
Chemical messengers released from axon terminals that cross the synaptic cleft and bind to receptors on the next neuron.
Reuptake
The process by which neurotransmitters are reabsorbed by the sending neuron after transmission.
Endocrine System
The body's chemical communication system using hormones secreted by glands into the bloodstream.
Amygdala
A limbic system structure involved in processing emotions, especially fear and aggression.
Hippocampus
A limbic system structure essential for forming new explicit (declarative) memories.
Hypothalamus
A brain structure that regulates hunger, thirst, body temperature, and the endocrine system via the pituitary gland.
Cerebral Cortex
The thin, wrinkled outer layer of the cerebrum responsible for higher-order thinking, planning, language, and consciousness.
Broca's Area
A region in the left frontal lobe that controls speech production. Damage causes Broca's aphasia (difficulty producing speech).
Wernicke's Area
A region in the left temporal lobe responsible for language comprehension. Damage causes Wernicke's aphasia (fluent but meaningless speech).
Corpus Callosum
A thick band of nerve fibers connecting the left and right hemispheres, allowing them to communicate.
Neuroplasticity
The brain's ability to reorganize itself by forming new neural connections throughout life, especially after injury or learning.
Circadian Rhythm
The body's 24-hour internal biological clock that regulates the sleep-wake cycle and other physiological processes.
REM Sleep
A stage of sleep characterized by rapid eye movements, vivid dreaming, and muscle atonia; important for memory consolidation.
Transduction
The conversion of physical energy (light, sound, etc.) into electrochemical neural impulses that the brain can process.
Absolute Threshold
The minimum stimulation needed to detect a particular stimulus 50% of the time.
Weber's Law
The principle that the just noticeable difference (JND) between two stimuli is a constant proportion of the original stimulus.
Signal Detection Theory
A theory predicting how and when we detect faint stimuli, taking into account not just stimulus strength but also psychological factors.
Sensory Adaptation
Diminished sensitivity to a constant, unchanging stimulus over time.
✍️ Practice Multiple-Choice Questions
Test your knowledge with 25 AP-style questions. Click "Show Answer" to reveal the correct answer and explanation.
1. A researcher finds that identical twins raised apart are more similar in personality than fraternal twins raised together. This finding best supports the influence of:
A) Environment over genetics
B) Genetics over environment
C) Epigenetics
D) Neuroplasticity
Answer: B) Since identical twins share 100% of their DNA and are more similar than fraternal twins (who share ~50%) even when raised in different environments, this supports a strong genetic influence on personality.
2. The parasympathetic nervous system is responsible for:
A) Activating the fight-or-flight response
B) Controlling voluntary muscle movements
C) Calming the body and restoring it to a resting state
D) Relaying sensory information to the thalamus
Answer: C) The parasympathetic nervous system activates the "rest-and-digest" response, slowing heart rate, stimulating digestion, and calming the body after a stressful event.
3. Which part of the neuron receives messages from other neurons?
A) Axon
B) Myelin sheath
C) Cell body
D) Dendrites
Answer: D) Dendrites are the branch-like extensions that receive incoming signals from other neurons and carry them toward the cell body.
4. The "all-or-nothing" principle refers to the fact that:
A) Neurotransmitters are either excitatory or inhibitory
B) A neuron either fires at full strength or does not fire at all
C) The brain can only process one type of information at a time
D) Sensory adaptation occurs completely or not at all
Answer: B) The action potential is an all-or-nothing event. Once the threshold is reached, the neuron fires at full strength. There is no partial firing.
5. Damage to the hippocampus would most likely result in difficulty with:
A) Regulating body temperature
B) Producing speech
C) Forming new long-term memories
D) Coordinating voluntary movements
Answer: C) The hippocampus is critical for forming new explicit (declarative) memories. Damage to this structure impairs the ability to create new long-term memories.
6. Which neurotransmitter is most directly associated with muscle contraction and memory, and is depleted in Alzheimer's disease?
A) Dopamine
B) Serotonin
C) GABA
D) Acetylcholine
Answer: D) Acetylcholine (ACh) plays a key role in muscle contraction and memory. Depleted ACh levels are associated with Alzheimer's disease.
7. A person who can understand language but struggles to produce fluent speech most likely has damage to:
A) Wernicke's area
B) The occipital lobe
C) Broca's area
D) The cerebellum
Answer: C) Broca's area (in the left frontal lobe) controls speech production. Damage causes Broca's aphasia: the person understands language but has difficulty speaking fluently.
8. During which stage of sleep do vivid dreams most commonly occur?
A) NREM Stage 1
B) NREM Stage 2
C) NREM Stage 3
D) REM sleep
Answer: D) REM (Rapid Eye Movement) sleep is when most vivid dreaming occurs. The brain is highly active during REM, resembling wakefulness.
9. Weber's Law is best illustrated by which of the following examples?
A) A person stops noticing the sound of a ticking clock after several minutes
B) A person can detect a 1-pound difference on a 10-pound package but needs a 10-pound difference on a 100-pound package
C) A person can hear a pin drop in a silent room
D) A person's pupils dilate in a dark room
Answer: B) Weber's Law states that the just noticeable difference (JND) is a constant proportion of the original stimulus. Detecting a difference is proportional to the magnitude of the initial stimulus.
10. The thalamus serves as the brain's relay station for all senses EXCEPT:
A) Vision
B) Hearing
C) Smell
D) Touch
Answer: C) Smell (olfaction) is the only sense that bypasses the thalamus, routing directly to the olfactory bulb and limbic system structures.
11. Epigenetics is best described as:
A) The study of how genes determine all behavior
B) The study of how the environment can change gene expression without altering DNA
C) The theory that behavior is entirely learned
D) The study of genetic mutations that cause mental disorders
Answer: B) Epigenetics studies how environmental factors (stress, diet, etc.) can alter gene expression through mechanisms like DNA methylation, without changing the DNA sequence itself.
12. The myelin sheath speeds up neural impulses through a process called:
A) Reuptake
B) Transduction
C) Saltatory conduction
D) Depolarization
Answer: C) Saltatory conduction is the process by which the action potential "jumps" between the Nodes of Ranvier (gaps in the myelin sheath), dramatically speeding up neural transmission.
13. The endocrine system communicates by using:
A) Electrical impulses along neurons
B) Neurotransmitters across synaptic gaps
C) Hormones released into the bloodstream
D) Glial cells throughout the brain
Answer: C) The endocrine system uses hormones, which are chemical messengers secreted by glands and transported through the bloodstream to target organs and tissues.
14. Phineas Gage's accident provided early evidence that the frontal lobe is involved in:
A) Visual processing
B) Language comprehension
C) Personality and impulse control
D) Memory formation
Answer: C) After the accident damaged his frontal lobe, Gage's personality changed dramatically — he became impulsive, irritable, and socially inappropriate, demonstrating the frontal lobe's role in personality and decision-making.
15. Night terrors differ from nightmares in that night terrors:
A) Occur during REM sleep
B) Are usually remembered in detail
C) Occur during NREM Stage 3 (deep sleep)
D) Involve only visual imagery
Answer: C) Night terrors occur during deep NREM sleep (Stage 3/N3), often with screaming and intense fear. They are typically not remembered. Nightmares, by contrast, occur during REM sleep and are often recalled.
16. Which brain structure acts as the "master gland" link, connecting the nervous system to the endocrine system?
A) Thalamus
B) Amygdala
C) Hypothalamus
D) Cerebellum
Answer: C) The hypothalamus directs the pituitary gland (the "master gland"), serving as the critical link between the nervous system and the endocrine system.
17. Sensory adaptation is best demonstrated by which of the following?
A) Hearing a fire alarm and immediately leaving the building
B) No longer smelling your own perfume after wearing it for an hour
C) Being unable to see in a dark movie theater at first
D) Tasting food more intensely when you are hungry
Answer: B) Sensory adaptation is the decreased sensitivity to a constant, unchanging stimulus. After wearing perfume for a while, you stop noticing it because your olfactory receptors have adapted.
18. The corpus callosum is primarily responsible for:
A) Regulating sleep cycles
B) Connecting the left and right hemispheres of the brain
C) Processing visual information
D) Controlling the fight-or-flight response
Answer: B) The corpus callosum is a thick band of nerve fibers that connects the two cerebral hemispheres, allowing them to communicate and share information.
19. Which type of photoreceptor is responsible for color vision and is concentrated in the fovea?
A) Rods
B) Cones
C) Ganglion cells
D) Bipolar cells
Answer: B) Cones are photoreceptors that detect color and fine detail. They are concentrated in the fovea, the central focal point of the retina.
20. An excess of dopamine activity is most closely associated with:
A) Parkinson's disease
B) Alzheimer's disease
C) Schizophrenia
D) Depression
Answer: C) Excess dopamine activity has been linked to schizophrenia (the dopamine hypothesis). Low dopamine, on the other hand, is associated with Parkinson's disease.
21. Sleep spindles and K-complexes are characteristic of which sleep stage?
A) NREM Stage 1
B) NREM Stage 2
C) NREM Stage 3
D) REM sleep
Answer: B) NREM Stage 2 (N2) is characterized by sleep spindles (bursts of rapid brain activity) and K-complexes. It makes up the largest portion of total sleep time.
22. The activation-synthesis theory suggests that dreams are:
A) The brain's way of fulfilling unconscious wishes
B) Random neural activity that the brain tries to make sense of
C) Rehearsals of threatening events for survival
D) The result of unresolved childhood conflicts
Answer: B) Hobson and McCarley's activation-synthesis theory proposes that during REM sleep, the brainstem generates random neural activity, and the cortex synthesizes (interprets) this activity into dream narratives.
23. Which brain imaging technique measures blood flow to determine which areas of the brain are active during a task?
A) EEG
B) CT scan
C) fMRI
D) MRI
Answer: C) Functional MRI (fMRI) detects changes in blood oxygenation and flow, revealing which brain regions are most active during specific tasks. Unlike a standard MRI, which only shows structure, fMRI shows brain activity.
24. A heritability estimate of 0.60 for a trait means that:
A) 60% of an individual's trait is determined by genes
B) 60% of the variation in that trait within a population is attributable to genetic differences
C) The trait is 60% nature and 40% nurture for every person
D) 60% of people in the population have the trait
Answer: B) Heritability refers to the proportion of variation in a trait within a population that can be attributed to genetic factors. It does NOT tell us how much of an individual person's trait is genetic.
25. Neuroplasticity is best demonstrated by which of the following scenarios?
A) A newborn baby has more neurons than an adult
B) A stroke patient gradually recovers language ability as other brain areas compensate
C) A person's reaction time decreases with age
D) A neurotransmitter is reabsorbed by the sending neuron
Answer: B) Neuroplasticity is the brain's ability to reorganize by forming new neural connections. A stroke patient recovering lost function through other brain areas taking over is a classic example of neuroplasticity.
