Unit 1: Biological Bases of Behavior

As a toddler, Ellie was cautious and quiet around strangers, much like her mother and grandmother. Her parents gently encouraged her to join a theater club, and by high school she was comfortable performing for an audience. Which statement best explains Ellie's development?

Researchers find that a reading disability is far more common among the parents and siblings of children with the disability than in the general population. They conclude that heredity causes the disability. What is the main weakness of this conclusion?

In an adoption study, researchers measured anxiety in adopted adolescents and in their biological and adoptive parents. The table shows the correlations. Which conclusion is best supported?

A team locates pairs of identical twins who were adopted into different families as infants and compares how similar each pair is in extraversion. Why is this design especially useful for studying heredity?

Late at night, Marcus hears glass break downstairs. His heart pounds, his breathing speeds up and his mouth goes dry. Which part of the nervous system is producing these responses?

A researcher tests whether watching a horror film clip activates the sympathetic nervous system more than watching a nature clip. Which is the best operational definition of sympathetic activation for this study?

Looking at stained brain tissue, a student sees many cells that do not send messages of their own but wrap axons in insulation, hold neurons in place and clear away waste. What are these cells?

Kai touches a hot pan and jerks his hand away before he even feels the pain. Which sequence best describes the reflex arc that moved his hand?

Jaylen claims that when someone presses lightly on his arm, his touch neurons fire weakly, and when someone presses hard, they fire strongly. Which principle shows what is wrong with his claim?

A neuron receives several excitatory messages at the same moment, along with a few inhibitory ones. Its charge becomes slightly less negative but it does not fire. Which explanation is most accurate?

In a lab demonstration, a neuron is stimulated strongly and fires. A second strong stimulus a fraction of a millisecond later produces no action potential, but the same stimulus a few milliseconds later does. What explains the missing response?

Gloria has multiple sclerosis. She has muscle weakness, blurred vision and trouble with coordination. Which explanation of her symptoms is most accurate?

A medication reduces anxiety and can help prevent seizures by strengthening the effect of the brain's main inhibitory neurotransmitter. Which neurotransmitter does the medication target?

A skin cream relieves the pain of arthritis by depleting the neurotransmitter that sensory neurons use to send pain signals toward the brain. Which neurotransmitter is the cream depleting?

After two drinks, Sam's reactions are slower, his speech is slightly slurred and he feels less inhibited. In which class of psychoactive drugs does alcohol belong?

A researcher posts a flyer at one college and recruits 60 students. She then uses a coin flip to give each student either an oxytocin nasal spray or a salt-water spray before a trust game. What does the coin flip accomplish?

Students are randomly assigned to drink a caffeinated or a decaffeinated coffee that taste the same, then take a memory test. Neither the students nor the research assistant who gives and scores the test knows who drank which. What is the main purpose of keeping the assistant unaware?

Volunteers were randomly assigned to receive one of four doses of caffeine, and their mean reaction time on a computer task was recorded. Lower times mean faster reactions. Which statement is best supported by the table?

A doctor explains that an overdose of an opioid can be fatal because the drug suppresses activity in the part of the brain that controls breathing and heart rate. Which structure is the doctor describing?

After a stroke damages a network of neurons running through the brain stem, a patient becomes very difficult to wake and cannot stay alert, although her cortex is undamaged. Which system was most likely damaged?

A patient with damage to one structure in the center of the brain has trouble processing sights, sounds and touch, but his sense of smell is normal. Which structure was most likely damaged?

After surgery that removed part of the temporal lobe on both sides, Tomas no longer shows the usual signs of fear when he sees a threatening animal, although he can describe it accurately. Which structure was most likely affected?

A map of the somatosensory cortex shows a much larger area for the lips and fingertips than for the back. Which statement best explains this pattern?

During brain surgery on an awake patient, a surgeon gently stimulates a strip at the rear of the left frontal lobe, and the fingers of the patient's right hand twitch. Which structure is being stimulated?

In split-brain experiments, researchers flash each image for only a fraction of a second to one side of a fixation point. Why is the brief flash an important part of the design?

To study eating, researchers destroy a small part of the hypothalamus in a group of rats and compare their food intake with that of rats given the same surgery without the destruction. What research approach is this?

In an fMRI study, participants' amygdala activity rose while they viewed angry faces. A news headline claims, "The amygdala creates anger." Which statement best evaluates the headline?

Halfway through an fMRI session, a participant says she feels anxious in the scanner and wants to stop. The researcher tells her she must finish or her data will be wasted. Which ethical principle has the researcher violated?

Rosa drives her usual route to school while thinking about a test. When she arrives, she cannot recall passing the familiar landmarks, although she drove safely. Which idea does this best illustrate?

After flying from Los Angeles to Paris, Andre is wide awake at 3 a.m. Paris time and struggles to stay awake during afternoon meetings. Which concept best explains his experience?

As Lily drifts off to sleep, she suddenly feels as if she is falling and jerks awake. She was asleep for less than a minute. Which statement best describes what happened?

A sleep technician sees an EEG with fast, irregular waves much like those of an awake person. The sleeper's eyes dart under the lids, yet the large muscles of the body are almost completely limp. Which stage is the sleeper most likely in?

The table shows the minutes one participant spent in NREM stage 3 and in REM sleep during each of five sleep cycles in one night. Which statement is supported by the data?

Noor dreams that she is swimming through a library while her old soccer coach reads aloud. Her psychology teacher says the dream is the brain's attempt to weave random bursts of neural activity during REM sleep into a story. Which theory is the teacher using?

After running a marathon, Theo sleeps several hours longer than usual and spends more time than usual in deep sleep. Which theory of why sleep occurs does this best support?

Mr. Okafor snores loudly, and his wife notices that he stops breathing for several seconds many times a night, then gasps. He feels exhausted every day even after eight hours in bed. Which sleep disorder best fits?

A survey finds that nurses who work night shifts report more errors at work than nurses who work day shifts. A hospital manager concludes that night shifts cause the errors. Which is the best criticism of this conclusion?

Volunteers stay awake for 30 hours in a sleep lab for a study of attention. At the end, the researchers let them drive themselves home. Which ethical principle is most clearly at risk?

Ten high school students recorded how many hours they slept on a school night: 3, 6.5, 7, 7, 7.5, 7.5, 8, 8, 8.5 and 9. Which statement best describes this distribution?

In a hearing test, a tone was played at five intensities, 50 times each, and the participant said whether she heard it. The table shows the percent of trials on which she detected the tone. What is her absolute threshold for this tone?

In a dark room, adding one lit candle to two lit candles makes an easily noticed difference in brightness. Adding one candle to 60 lit candles does not. Which principle explains this?

Cells in the retina convert the energy of light into neural signals that travel to the brain. What is this conversion called?

With one eye closed, Javier stares at a cross on a card and moves the card closer. At one distance, a dot beside the cross vanishes, and he sees plain white paper in its place. Which explanation is most accurate?

Priya can read her phone clearly, but the board at the front of the classroom looks blurry. Her eye doctor says the images of distant objects come into focus in front of her retina. Which condition does she have?

A phone screen produces every color it displays by mixing only red, green and blue light in different amounts. Which theory of color vision does this most directly reflect?

Testing shows that Carlos has only two working types of cones, so he confuses some reds and greens but sees blues and yellows normally. Which term best describes his condition?

After a stroke damaged her left occipital lobe, Ms. Reyes says she sees nothing in her right visual field. Yet when asked to guess whether an object there is moving up or down, she guesses correctly far more often than chance. Which term describes this?

After repeated ear infections, Liam's eardrum is scarred and the tiny bones of his middle ear move poorly. His cochlea and auditory nerve are healthy. Which statement best describes his hearing loss?

Blindfolded in a sound lab, Ana easily tells whether a click comes from her left or right. She often confuses clicks from directly in front of her with clicks from directly behind her. Which explanation is best?

A neurologist notes that a small injury to a patient's thalamus has disrupted his vision, hearing and touch, but not his sense of smell. Which fact explains why smell was spared?

After banging his elbow on a desk, Omar rubs the spot hard, and the pain eases. Which theory best explains why rubbing reduces the pain?

After spinning on a playground ride, Zoe feels dizzy and the world seems to keep turning for a few seconds after she stops. Which sense, detected mainly by the semicircular canals, is involved?

With his eyes closed, a basketball player can tell exactly how bent his elbow is and can bring his fingertip to his nose. Which sense makes this possible?

To study supertasters, a researcher recruits 40 volunteers from a culinary school and finds that 45% of them are supertasters. She concludes that 45% of all adults are supertasters. What is the main problem with her conclusion?

Researchers measured the quietest high-pitched tone (in decibels) that each of 8 young adults and 8 older adults could detect. Higher values mean worse hearing. Which statement is supported by the data?

When Grace walks into her grandmother's kitchen, the smell of garlic is strong. Twenty minutes later she no longer notices it, although the smell has not faded. Which concept explains this?

After damage to part of his visual cortex, Mr. Abara can describe the shape of a nose and the color of eyes in a photo, but he cannot tell that the photo shows his own daughter until she speaks. Which condition does he most likely have?

To test whether mirror therapy reduces phantom limb pain, researchers randomly assign 30 people who have lost a leg to two groups. One group watches the reflection of the remaining leg move in a mirror; the other group does the same sessions with the mirror covered. Why include the covered-mirror group?

Participants eat jelly beans of different flavors, once with their noses pinched shut and once with their noses open, and try to name each flavor. What is the independent variable?

Brain scans show that professional violinists have more somatosensory cortex devoted to the fingers of the left hand than people who do not play. Why can't the researchers conclude that years of practice caused this difference?

Cocaine blocks the sending neuron from reabsorbing dopamine, so dopamine stays active in the synapse. A user feels energetic and euphoric. Which statement best classifies cocaine?

Just before lunch, Tasha's stomach growls and she feels very hungry. After a large meal, her fat cells release a hormone that signals she has had enough. Which pair of hormones is described, in order?

Two years after his arm was amputated, Mr. Haddad still sometimes feels an itch on the missing hand. Which statement best explains this experience?