AP Psychology Unit 1 Practice Test: Biological Bases of Behavior MCQs (Free PDF)

Here's a free AP Psychology Unit 1 practice test: 20 AP-style MCQs on biological bases of behavior, seven scenario and data stimuli, and a full rationale for every answer, all aligned to the 2024-25 CED.

Below, three mistakes I see students make on Unit 1 and how to avoid them, plus one worked example so you can see the reasoning.

Unit 1 is 15-25% of the exam (every unit is weighted equally under the redesigned CED, so no single unit is "the biggest"). What makes Unit 1 different is that it sets up the vocabulary the other four units lean on: neurons, neurotransmitters, brain regions, sleep stages, sensation. Get these labels wrong in Unit 1 and Units 2, 3 and 5 quietly get harder too. For the full 5-unit map, see our AP Psychology units guide.

AP Psych MCQs mostly don't ask you to recall a definition in isolation. The 75-question multiple-choice section leans stimulus-heavy: many items sit on a scenario, a data table, a research vignette or a graph, and you're expected to apply the concept, not just name it.

One framing point matters more than any other for Unit 1: the CED states that MCQs on this unit test functions, not structures. The Unit 1 overview on p. 30 says students will be asked about the process of neural communication, but not asked to identify parts of a neuron. So a brain-region stem is usually really a "what does this part do?" question. For the wider research-skill lens, our AP Psychology research methods guide covers the study designs Unit 1 loves to test.

Common stimulus formats on Unit 1 items include:

• Twin, family and adoption studies with correlation tables (heredity vs environment)
• Fight-or-flight vignettes that test autonomic nervous system branches
• Drug-effect stems that turn on agonist vs antagonist and excitatory vs inhibitory
• Lesion tables that map an impairment to a brain region
• EEG segments matched to NREM stages and REM
• Kinesthesis and sensation scenarios (a soccer player, a watchband, a startling sound)

The practice test in the PDF mirrors that mix. Each item is tagged to a Unit 1 topic (1.1 through 1.6) and to a named AP Psych Science Practice.

Every year I see students walk into Unit 1 MCQs making the same three moves. Two of the three match up with recent Chief Reader Reports, so catching yourself doing any of them buys you marks with no extra content revision.

Students routinely mix up amplitude and frequency when a stem describes a loud crash, a quiet whisper or any auditory scenario. Amplitude is the height of the wave and it determines loudness; frequency (waves per second) determines pitch. The 2023 AP Psychology Chief Reader Report flagged this directly, noting that responses often described an incorrect relationship between amplitude and loudness.

The right framing on any Unit 1.6 sound item: high amplitude = loud, low amplitude = quiet; high frequency = high pitch, low frequency = low pitch. Any stem mentioning decibels, volume or a startling sound is testing amplitude, not frequency.

Kinesthesis routinely gets defined as "knowing how to move your body" rather than "sensing where your body parts are as they move". The 2024 AP Psychology Chief Reader Report (Set 2) flagged this one on Q1: many responses described knowledge for how to position or move the body instead of the actual definition.

Kinesthesis is a sensory system, not a motor system. It tells you your arm is bent at 90 degrees without looking. It lives alongside the vestibular sense (whole-body balance) under Topic 1.6, and both are sensory receptors feeding the brain, not motor commands leaving it. If a stem describes an athlete trapping a ball without looking down, that's kinesthetic sensation, not motor cortex output.

Ghrelin trips students up because it's a hormone, not a neurotransmitter, and its job in the hunger loop is easy to invert. Ghrelin was tested on the 2023 AP Psychology free-response, and the mistake I keep seeing in mock papers is students calling it a "brain chemical" and putting it in the same bucket as dopamine or serotonin. The 2024-25 CED is explicit that neurotransmitters and hormones are separate categories with different transport routes: neurotransmitters cross synapses in the nervous system; hormones travel through the bloodstream from the endocrine system.

The CED caps the tested hormone list at five (adrenaline, leptin, ghrelin, melatonin, oxytocin) and the tested neurotransmitter list at eight (dopamine, serotonin, norepinephrine, glutamate, GABA, endorphins, substance P, acetylcholine). Two clean rules for ghrelin: it's a hormone that signals hunger (rises when you haven't eaten, falls after a meal); leptin is its counterpart from fat cells that signals fullness. Any MCQ naming a hormone and asking about mechanism is asking about blood-borne signaling and the endocrine system, not synaptic transmission.

Here's a question straight from the Unit 1 pack. The stimulus: researchers compared identical twins raised together, identical twins raised apart, and fraternal twins raised together on a standardized measure of extraversion. All participants were adults, and the researchers reported correlation coefficients for the extraversion scores within each pair.

The stem: "Which conclusion is best supported by the correlations shown in Table 1?"

• (A) Extraversion is driven mainly by shared home environment, since the twins-raised-together correlation is the highest of the three.
• (B) Extraversion has a heritable component, since identical pairs still correlate more strongly than fraternal pairs even when reared apart.
• (C) Fraternal twins share about the same amount of genetic material as identical twins, so the differences in correlation must reflect the effect of home environment on this trait.
• (D) A correlational study of this type cannot support any inference about a genetic contribution to extraversion.

Answer: B. Identical twins share about 100% of their DNA and fraternal twins about 50%. Identical pairs correlate more strongly (0.55, 0.38) than fraternal pairs (0.20), even when reared apart, which points to a heritable component. A ignores that identicals raised apart still resemble each other. C is factually wrong about twin biology: fraternal twins share less genetic material than identical twins, not the same amount. D overstates the limit: twin studies are the standard tool for estimating heritability.

The CED is explicit about Unit 1: the multiple-choice section tests functions, not anatomy. The exact wording is that students will be asked about the process of neural communication, but they will not be asked to identify parts of the neuron.

So when you're studying, spend your time on what each part does, not on labeling diagrams. For every brain region on the CED list, be able to finish this sentence in one line: "Damage to X causes Y, because X handles Z." Same for neurotransmitters: know what each one does to behavior, not the chemistry of its receptor.

If you catch yourself memorizing diagrams or spelling of structures, you're studying the wrong thing. The stems will describe a scenario or a lesion effect and ask you to reason about function; you already have the diagram in the question.

Source: AP Psychology CED, Unit 1 overview p. 30.

The current CED lists eight tested neurotransmitters (dopamine, serotonin, norepinephrine, glutamate, GABA, endorphins, substance P, acetylcholine) and five tested hormones (adrenaline, leptin, ghrelin, melatonin, oxytocin). Anything clearly outside those lists (histamine, cortisol, insulin, aldosterone) tends not to be the intended answer on Unit 1 items.

Other Unit 1 exclusions worth knowing: sodium-potassium pump mechanics, the psychoanalytic theory of dreams, and endocrine glands beyond the pituitary. If a distractor turns on one of those excluded mechanisms, it's worth ruling out before evaluating meaning. Note that genetics vocabulary (genotype, phenotype, DNA, dominant vs recessive) is capped rather than fully excluded; the CED says stems won't turn on that specific detail, but general concepts like "identical twins share ~100% of their DNA" are still fair game in a twin-study stimulus.

A lot of Topic 1.3 stems on drug effects, disorders or behavior changes come down to whether you know if a neurotransmitter is excitatory or inhibitory, and where it acts.

• GABA is the main inhibitory neurotransmitter. Drugs that mimic it (agonists) calm the nervous system, which is why anti-anxiety medications often target GABA receptors.
• Glutamate is the main excitatory neurotransmitter throughout the cortex.
• Dopamine is involved in reward and movement; Parkinson's disease reflects a loss of dopamine in motor pathways.
• Serotonin is involved in mood regulation; low serotonin activity is one factor associated with depression, though modern accounts describe depression as multi-factor rather than a straight "low serotonin" story.
• Acetylcholine controls muscle contraction at the neuromuscular junction and supports memory in the hippocampus; Alzheimer's disease involves acetylcholine loss.

On a drug-effect stem, note whether the outcome is "more activity" or "less activity" and match to the neurotransmitter that would produce that pattern. The same reasoning covers questions about agonists (mimic the effect) and antagonists (block it).

I recommend a three-pass method.

• First, an untimed pass: no clock, no pressure, roughly 90 seconds per question. The goal is diagnostic. You want to see whether you can reason from the stimulus at all, and to flag any Unit 1 topics you keep missing.
• Second, a timed pass one week later: 24 minutes for 20 questions, which matches the AP exam pace of about 72 seconds per MCQ (90 minutes across 75 questions).
• Third, a review pass: check the answer key, then revise weak topics on Cognito's AP Psychology notes before you retry the missed questions a week after that.

The gap between passes is where the learning sticks. For general study habits across the whole course, see how to study for AP Psychology.