Unit 1: Biological Bases of Behavior

22 terms. Say what each one means, then open the card to check.

• Operational definition

  A precise statement of how a variable will be measured or produced in a study, so others can repeat it.

  Example. A researcher defines stress as a student's score on a 10-question stress survey taken right before a test.

• Independent variable

  The factor a researcher changes on purpose in an experiment to see whether it affects something else.

  Example. In a study of caffeine and reaction time, the amount of caffeine each group drinks is the independent variable.

• Confounding variable

  A factor other than the independent variable that differs between groups and could explain the result instead.

  Example. If the group using a study app also sleeps more, sleep becomes a confounding variable for higher test scores.

• Random assignment

  Placing participants into groups purely by chance, so the groups start out about the same before the treatment.

  Example. A coin flip decides whether each volunteer joins the exercise group or the no-exercise group.

• Correlation coefficient

  A number from -1 to +1 that shows the direction and strength of a link between two variables, without showing cause.

  Example. An r of -0.70 between hours of gaming and grades means more gaming tends to go with lower grades.

• Heritability

  An estimate of how much of the variation in a trait within a group is linked to genetic differences in that group.

  Example. A heritability of 0.5 for shyness in a sample describes the group, not how shy any one person is because of genes.

• Twin study

  A study that compares identical twins with fraternal twins to estimate how much genes and environment shape a trait.

  Example. If identical twins match on anxiety more often than fraternal twins do, genes likely play a role in anxiety.

• Epigenetics

  The study of how experiences and the environment can turn genes on or off without changing the DNA code itself.

  Example. Severe early stress may change which genes are active in a child, even though the child's DNA stays the same.

• Sympathetic nervous system

  The branch of the autonomic nervous system that arouses the body for action by speeding the heart and breathing.

  Example. When a dog suddenly barks behind you, your heart races and your pupils widen.

• Parasympathetic nervous system

  The branch of the autonomic nervous system that calms the body and saves energy after arousal.

  Example. After a close call on the road, your heart rate slowly drops and your breathing evens out.

• Reflex arc

  A quick, automatic pathway from a sensory neuron through the spinal cord to a motor neuron, before the brain is involved.

  Example. You jerk your foot away from a sharp tack before you even feel the pain.

• Action potential

  A brief electrical signal that moves down a neuron's axon once the neuron is pushed past its threshold.

  Example. A firm tap on your arm pushes touch neurons past threshold, and each one fires a full-size signal.

• Reuptake

  The process in which the sending neuron pulls leftover neurotransmitter back in from the synapse.

  Example. Some antidepressants slow the reuptake of serotonin, so serotonin stays in the synapse longer.

• Agonist

  A chemical that mimics a neurotransmitter or increases its effect at the receptor.

  Example. Morphine acts like the body's own endorphins, binding to the same receptors and easing pain.

• Broca's area

  A region of the frontal lobe, usually in the left hemisphere, that helps produce spoken language.

  Example. After damage to this area, a woman understands a question but answers with slow, broken phrases.

• Corpus callosum

  A thick band of nerve fibers that links the left and right hemispheres so they can share information.

  Example. When this band is cut to stop severe seizures, each hemisphere can no longer easily share what it sees.

• Neuroplasticity

  The brain's ability to change its structure and connections in response to experience or injury.

  Example. A child who loses function on one side after an injury may regain it as other brain areas take over the task.

• Circadian rhythm

  The body's internal cycle of about 24 hours that regulates alertness, body temperature and sleep.

  Example. You feel wide awake at noon and sleepy near your usual bedtime, even without checking a clock.

• REM sleep

  A sleep stage with rapid eye movements, vivid dreams, an active brain and large muscles that are mostly still.

  Example. A sleeper's eyes dart under closed lids, and if woken, she reports a detailed dream.

• Transduction

  The conversion of physical energy, such as light or sound waves, into neural signals by sensory receptors.

  Example. Hair cells in the cochlea bend with sound waves and turn that motion into signals sent to the brain.

• Weber's law

  The rule that the smallest change we can notice is a constant proportion of the original stimulus, not a fixed amount.

  Example. You notice one extra book in a light backpack, but one extra book in a heavy backpack may go unnoticed.

• Sensory adaptation

  A drop in sensitivity to a stimulus that does not change, so we stop noticing it over time.

  Example. A strong smell in a bakery fades from notice a few minutes after you walk in.