0.1

critical thinking

thinking that does not automatically accept arguments and conclusions. Rather, it examines assumptions, appraises the source, discerns hidden biases, evaluates evidence, and assesses conclusions.

0.2

hindsight bias

the tendency to believe, after learning an outcome, that one would have foreseen it. (Also known as the I-knew-it-all-along phenomenon.)

0.3

peer reviewers

scientific experts who evaluate a research article’s theory, originality, and accuracy.

0.3

theory

an explanation using an integrated set of principles that organizes observations and predicts behaviors or events.

0.3

hypothesis

a testable prediction, often implied by a theory.

0.3

operational definition

a carefully worded statement of the exact procedures (operations) used in a research study. For example, human intelligence may be operationally defined as what an intelligence test measures. (Also known as operationalization.)

0.3

replication

repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding can be reproduced.

0.3

case study

a non-experimental technique in which one individual or group is studied in depth in the hope of revealing universal principles.

0.3

naturalistic observation

a non-experimental technique of observing and recording behavior in naturally occurring situations without trying to manipulate and control the situation.

0.3

survey

a non-experimental technique for obtaining the self-reported attitudes or behaviors of a particular group, usually by questioning a representative, random sample of the group.

0.3

social desirability bias

bias from people’s responding in ways they presume a researcher expects or wishes.

0.3

self-report bias

bias when people report their behavior inaccurately.

0.3

sampling bias

a flawed sampling process that produces an unrepresentative sample.

0.3

random sample

a sample that fairly represents a population because each member has an equal chance of inclusion.

0.3

population

all those in a group being studied, from which samples may be drawn. (Note: Except for national studies, this does not refer to a country’s whole population.)

0.4

correlation

a measure of the extent to which two factors vary together, and thus of how well either factor predicts the other.

0.4

correlation coefficient

a statistical index of the relationship between two things (from −1.00 to +1.00).

0.4

variable

anything that can vary and is feasible and ethical to measure.

0.4

scatterplot

a graphed cluster of dots, each of which represents the values of two variables. The slope of the points suggests the direction of the relationship between the two variables. The amount of scatter suggests the strength of the correlation (little scatter indicates high correlation).

0.4

illusory correlation

perceiving a relationship where none exists, or perceiving a stronger-than-actual relationship.

0.4

regression toward the mean

the tendency for extreme or unusual scores or events to fall back (regress) toward the average.

0.4

experiment

a research method in which an investigator manipulates one or more factors (independent variables) to observe the effect on some behavior or mental process (the dependent variable). By random assignment of participants, the experimenter aims to control other relevant factors.

0.4

experimental group

in an experiment, the group exposed to the treatment, that is, to one version of the independent variable.

0.4

control group

in an experiment, the group not exposed to the treatment; contrasts with the experimental group and serves as a comparison for evaluating the effect of the treatment.

0.4

random assignment

assigning participants to experimental and control groups by chance, thus minimizing preexisting differences between the different groups.

0.4

single-blind procedure

an experimental procedure in which the research participants are ignorant (blind) about whether they have received the treatment or a placebo.

0.4

double-blind procedure

an experimental procedure in which both the research participants and the research staff are ignorant (blind) about whether the research participants have received the treatment or a placebo. Commonly used in drug-evaluation studies.

0.4

placebo effect

experimental results caused by expectations alone; any effect on behavior caused by the administration of an inert substance or condition, which the recipient assumes is an active agent.

0.4

independent variable

in an experiment, the factor that is manipulated; the variable whose effect is being studied.

0.4

confounding variable

in an experiment, a factor other than the factor being studied that might influence a study’s results.

0.4

experimenter bias

bias caused when researchers may unintentionally influence results to confirm their own beliefs.

0.4

dependent variable

in an experiment, the outcome that is measured; the variable that may change when the independent variable is manipulated.

0.4

validity

the extent to which a test or experiment measures or predicts what it is supposed to. (See also predictive validity.)

0.5

quantitative research

a research method that relies on quantifiable, numerical data.

0.5

qualitative research

a research method that relies on in-depth, narrative data that are not translated into numbers.

0.5

informed consent

giving potential participants enough information about a study to enable them to choose whether they wish to participate.

0.5

debriefing

the postexperimental explanation of a study, including its purpose and any deceptions, to its participants.

1.3a

neuron

a nerve cell; the basic building block of the nervous system.

1.3a

cell body

the part of a neuron that contains the nucleus; the cell’s life-support center.

1.3a

dendrites

a neuron’s often bushy, branching extensions that receive and integrate messages, conducting impulses toward the cell body.

1.3a

axon

the segmented neuron extension that passes messages through its branches to other neurons or to muscles or glands.

1.3a

myelin sheath

a fatty tissue layer segmentally encasing the axons of some neurons; it enables vastly greater transmission speed as neural impulses hop from one node to the next.

1.3a

glial cells (glia)

cells in the nervous system that support, nourish, and protect neurons; they may also play a role in learning, thinking, and memory.

1.3a

action potential

a neural impulse; a brief electrical charge that travels down an axon.

1.3a

threshold

the level of stimulation required to trigger a neural impulse.

1.3a

refractory period

in neural processing, a brief resting pause that occurs after a neuron has fired; subsequent action potentials cannot occur until the axon returns to its resting state.

1.3a

all-or-none response

a neuron’s reaction of either firing (with a full-strength response) or not firing.

1.3a

synapse

the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic gap or synaptic cleft.

1.3a

neurotransmitters

chemical messengers that cross the synaptic gaps between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse.

1.3a

reuptake

a neurotransmitter’s reabsorption by the sending neuron.

1.3a

endorphins

“morphine within” — natural, opioid-like neurotransmitters linked to pain control and to pleasure.

1.3a

agonist

a molecule that increases a neurotransmitter’s action.

1.3a

antagonist

a molecule that inhibits or blocks a neurotransmitter’s action.

1.4b

hindbrain

consists of the medulla, pons, and cerebellum; directs essential survival functions, such as breathing, sleeping, and wakefulness, as well as coordination and balance.

1.4b

midbrain

found atop the brainstem; connects the hindbrain with the forebrain, controls some motor movement, and transmits auditory and visual information.

1.4b

forebrain

consists of the cerebral cortex, thalamus, and hypothalamus; manages complex cognitive activities, sensory and associative functions, and voluntary motor activities.

1.4b

brainstem

the central core of the brain, beginning where the spinal cord swells as it enters the skull; the brainstem is responsible for automatic survival functions.

1.4b

medulla

the hindbrain structure that is the brainstem’s base; controls heartbeat and breathing.

1.4b

thalamus

the forebrain’s sensory control center, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla.

1.4b

reticular formation

a nerve network that travels through the brainstem into the thalamus; it filters information and plays an important role in controlling arousal.

1.4b

cerebellum

the hindbrain’s “little brain” at the rear of the brainstem; its functions include processing sensory input, coordinating movement output and balance, and enabling nonverbal learning and memory.

1.4b

limbic system

neural system located mostly in the forebrain — below the cerebral hemispheres — that includes the amygdala, hypothalamus, hippocampus, thalamus, and pituitary gland; associated with emotions and drives.

1.4b

amygdala

two lima-bean-sized neural clusters in the limbic system; linked to emotion.

1.4b

hypothalamus

a limbic system neural structure lying below (hypo) the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system, and is linked to emotion and reward.

1.4b

hippocampus

a neural center located in the limbic system; helps process explicit (conscious) memories — of facts and events — for storage.

1.4b

cerebral cortex

the intricate fabric of interconnected neural cells covering the forebrain’s cerebral hemispheres; the body’s ultimate control and information-processing center.

1.4b

frontal lobes

the portion of the cerebral cortex lying just behind the forehead. They enable linguistic processing, muscle movements, higher-order thinking, and executive functioning (such as making plans and judgments).

1.4b

parietal lobes

the portion of the cerebral cortex lying at the top of the head and toward the rear; it receives sensory input for touch and body position.

1.4b

occipital lobes

the portion of the cerebral cortex lying at the back of the head; it includes areas that receive information from the visual fields.

1.4b

temporal lobes

the portion of the cerebral cortex lying roughly above the ears; it includes the auditory areas, each of which receives information primarily from the opposite ear. They also enable language processing.

1.4b

motor cortex

a cerebral cortex area at the rear of the frontal lobes that controls voluntary movements.

1.4b

somatosensory cortex

a cerebral cortex area at the front of the parietal lobes that registers and processes body touch and movement sensations.