AP Psychology Unit 1: Biological Bases of Behavior

Unit 1 covers the biological bases of behaviour: the nervous system, neurotransmission, brain structures, sensation and perception. It is the unit most often tested through a described case — a lesion, a deficit — that you match to a structure.

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288 questions6 CED topics100% with a figure
How this unit behaves

What 288 questions on it look like

This is the largest unit in AP Psychology by practice volume — 288 questions against the subject's other units. Weight your revision accordingly.

100% of the questions come with a figure — a graph, diagram or data display. Reading the figure correctly is most of the work before any content knowledge applies.

The Brain65
Sensation57
Overview of the Nervous System44
Sleep43
The Neuron and Neural Firing41
Interaction of Heredity and Environment38

Questions per CED topic.

From the bank

Three real biological bases of behavior questions

Drawn from the practice pool, not from the mock papers.

Interaction of Heredity and Environment · Concept Application · with figure

Two adolescents have a family history of anxiety. One attends a school with predictable routines and supportive adults; the other changes schools twice in a year and reports frequent conflict at home. Only the second adolescent begins avoiding classes. Which explanation is most consistent with the pattern?

  1. AInherited vulnerability can be expressed differently when daily surroundings differ.correct
  2. BMaturation alone determines whether emotional behavior changes over time.
  3. CSensory receptors become less responsive after repeated exposure to the same stimulus.
  4. DRandom assignment is required before a behavior can be described scientifically.
Why A is correct

The best answer explains why similar inherited risk can lead to different behavior when environments differ.

heredity-environment interaction explains the evidence in "Two adolescents have a family history of anxiety.". The credited option, "Inherited vulnerability can be expressed differently when daily surroundings differ", is supported because The scenario combines a shared family risk with different environmental conditions, so an interaction account is appropriate. "Maturation alone determines whether emotional behavior changes over time" is a real-looking alternative, but Maturation would focus on age-linked biological change, not different surroundings for adolescents with similar risk; "Sensory receptors become less responsive after repeated exposure to the same..." also fails because Sensory adaptation concerns reduced receptor response, not the onset of avoidance behavior. The aim is to connect the concrete evidence to the psychological mechanism, then reject choices that shift the process, time frame, or research logic away from the scenario pattern.

Common mistakes. "Maturation alone determines whether emotional behavior changes over time" is the first trap: Maturation would focus on age-linked biological change, not different surroundings for adolescents with similar risk. "Sensory receptors become less responsive after repeated exposure to the same stimulus" is different but still misses the task because sensory adaptation concerns reduced receptor response, not the onset of avoidance behavior.

Overview of the Nervous System · Concept Application · with figure

After narrowly missing a bicyclist, a driver notices a pounding heart, tense muscles, and rapid breathing. Several minutes later, the driver's breathing slows and digestion feels normal again. Which nervous-system process best explains the later change?

  1. AThe somatic system sends a voluntary command to skeletal muscles.
  2. BParasympathetic activity helps return internal functions toward a resting state.correct
  3. CA spinal reflex bypasses the brain to produce an immediate withdrawal response.
  4. DThe motor cortex stores the emotional memory of the event.
Why B is correct

The scenario asks about recovery after a threat response; parasympathetic activity best fits that task.

"After narrowly missing a bicyclist, a driver notices a pounding heart, tense muscles, and rapid breathing." details toward parasympathetic activity, not just a familiar Biological Bases of Behavior label. The credited option, "Parasympathetic activity helps return internal functions toward a resting state", is supported because The parasympathetic branch supports recovery and maintenance after sympathetic arousal. "A spinal reflex bypasses the brain to produce an immediate withdrawal response" is a real-looking alternative, but A reflex describes a fast protective action, not minutes-long recovery after danger; "The motor cortex stores the emotional memory of the event" also fails because The motor cortex is not responsible for restoring digestion and breathing after arousal. The aim is to connect the concrete evidence to the psychological mechanism, then reject choices that shift the process, time frame, or research logic away from the scenario pattern.

Common mistakes. spinal reflex bypasses the attracts students who answer by topic familiarity; the flaw is that a reflex describes a fast protective action, not minutes-long recovery after danger. motor cortex stores the has its own problem: the motor cortex is not responsible for restoring digestion and breathing after arousal.

The Neuron and Neural Firing · Concept Application · with figure

In a classroom demonstration, a neuron model fires only after enough small inputs are added together. Adding even more input does not make a single impulse larger. Which neural principle is being modeled?

  1. AMyelin prevents communication between neighboring neurons.
  2. BAntagonists increase a neurotransmitter's usual effect at the receptor.
  3. CEach impulse follows an all-or-none pattern once threshold is reached.correct
  4. DHormones travel only across synaptic gaps.
Why C is correct

The key evidence is that the impulse occurs after threshold and is not larger when extra input is added.

all-or-none principle is the mechanism that makes "In a classroom demonstration, a neuron model fires only after enough small inputs are added..." coherent. The credited option, "Each impulse follows an all-or-none pattern once threshold is reached", is supported because The model shows threshold and a fixed-size impulse, which is the all-or-none principle. "Hormones travel only across synaptic gaps" is a real-looking alternative, but Hormones travel through the bloodstream, not only across synapses; "Myelin prevents communication between neighboring neurons" also fails because Myelin generally speeds neural transmission rather than preventing it. The aim is to connect the concrete evidence to the psychological mechanism, then reject choices that shift the process, time frame, or research logic away from the scenario pattern.

Common mistakes. "Myelin prevents communication between neighboring neurons" should be crossed out for this reason: Myelin generally speeds neural transmission rather than preventing it. "Hormones travel only across synaptic gaps" is no safer, because hormones travel through the bloodstream, not only across synapses.

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FAQ

Biological Bases of Behavior questions

How much neuroanatomy do I need?

The major structures and what each does. Questions describe a deficit and ask which area it implicates, rather than asking for labels.

What is the difference between sensation and perception?

Sensation is detecting a stimulus; perception is organising and interpreting it. Top-down processing questions turn on that distinction.
Last reviewed 2026-08-28. Unit and topic names follow the College Board course framework. Question counts describe the PrepScore practice bank, not the exam.
Topic by topic

Worked questions by topic

6 of this unit’s topics have enough practice questions for a page of their own.

Interaction of Heredity and Environment38 questionsOverview of the Nervous System44 questionsThe Neuron and Neural Firing41 questionsThe Brain65 questionsSleep43 questionsSensation57 questions
Same course
Unit 2: Cognition288 questionsUnit 3: Development and Learning288 questionsUnit 4: Social Psychology and Personality288 questionsUnit 5: Mental and Physical Health288 questions

Practise biological bases of behavior until the reasoning is automatic.

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