Stanford Psych 1 Midterm 1

variable

Any characteristic whose value can change.

testable hypothesis

A prediction that has been formulated specifically enough so that it is clear what observations would confirm the prediction and what observations would challenge it.

operational definition

A definition that translates the variable we want to assess into a specific procedure or measurement.

dependent variable

The variable that is measured or recorded in an experiment.

independent variable

The variable that the experimenter manipulates as a basis for making predictions about the dependent variable.

population

The entire group about which the investigator wants to draw conclusions.

sample

The subject of the population that the investigator studies in order to learn about the population at large.

random sampling

A procedure in which every member of the population has an equal chance of being picked to participate in a study.

case study

An intensive study of one person.

external validity

The degree to which a study's participants, stimuli, and procedures adequately reflect the world as it actually is.

demand characteristics

The cues in a study that might tell a research participant what behaviors are expected or desired in that setting.

double-blind design

The technique of assigning participants to experimental conditions while keeping both the participants and the researchers unaware of who is assigned to which group.

descriptive statistics

Mathematical procedures that allow a researcher to characterize a data pattern; these procedures include measures of central tendency and of variability.

inferential statistics

Mathematical procedures that allow a researcher to draw further claims from a data pattern, including claims about whether the pattern observed in the sample is likely to be observed in other samples.

mean (M)

A measure of central tendency computed by calculating the sum of all the observations, then dividing by the number of observations.

median

A measure of central tendency taken by putting the data values in order and finding the value that divides the distribution in half.

variability

The degree to which scores in a frequency distribution depart from the central value.

standard deviation (SD)

A measure of the variability of a data set, calculated as the square root of the variance (V).

correlation

The tendency of two variables to change together. If one goes up as the other goes up, the correlation is positive; if one goes up as the other goes down, the correlation is negative.

correlation coefficient

A number that expresses both size and the direction of a correlation, varying from +1.00 (perfect positive correlation) to a -1.00 (perfect negative correlation).

reliability

The degree of consistency with which a test measures a trait or attribute.

validity

The extent to which a method or procedure measures what it is supposed to measure.

effect size

The magnitude of the difference between groups in a study, often computed by subtracting the mean of one group's scores from the mean the other's scores.

statistical significance

A calculation central to inferential statistics that describes the likelihood that the results of a study happen by chance.

quasi-experiment

A comparison that relies on already-existing groups (i.e., groups the experimenter did not create).

correlational studies

Studies in which the investigator analyzes the relationships among variables that were in place before the study without manipulating those variables.

third-variable problem

The possibility that two correlated variables may be changing together due to the operation of a third variable.

experiment

A study of casual relationships in which the researcher manipulates an independent variable to examine its effects on a dependent variable.

experimental manipulation

The deliberate alteration of the independent variable in an experiment in order to learn about its effects on the dependent variable.

experimental group

The group within an experiment that experiences the researcher's experimental manipulation of the independent variable.

control group

A group within an experiment that does not experience the experimental manipulation.

random assignment

In an experimental design, the random placement of participants in either the experimental or control groups, ensuring that the groups are matched at the outset of the experiment.

within-subject comparisons

Within a study, comparing the data about each participant in one situation to data about the same participant in another situation.

between-subject comparisons

Within a study, comparing one group of individuals to another group.

internal validity

The characteristic of a study that allows us to conclude that the manipulation of the independent variable caused the observed changes in the dependent variable.

replication

A repetition of an experiment that yields the same results.

meta-analysis

A statistical technique for combining the results of many studies on a particular topic, even when the studies used different data collection methods.

informed consent

A research participant's agreement to take part in the study, based on full information about what the experiment will involve.

debriefing

A step at the end of an experiment in which the researcher explains the study's purpose and design to each participant and undoes any manipulations to participant's beliefs or state.

empirical claims

Claims that can be true or false depending on the facts.

chromosomes

Structures in the nucleus of each cell that contain the genes, the units of hereditary transmission. A human cell has 46 chromosomes arranged in 23 pairs.

DNA (deoxyribonucleic acid)

The complex molecule that is the constituent of genes.

gene

A section of a DNA molecule that contains instructions for how and when to assemble a protein. Genes are located on chromosomes.

genotype

The complete set of an organism's genes.

phenotype

The overt characteristics and behaviors of an organism.

allele

An alternative form of a specific gene.

dominant

A term for a gene that directs the development of a particular characteristic even when the corresponding gene on the other chromosome is different-i.e., some other allele.

recessive

A term for a gene that directs the development of a particular characteristic only if the corresponding gene on the other chromosome matches it-i.e., the same allele.

polygenic inheritence

A pattern in which many genes all influence a single trait.

proximate cause

The influences within an organism's lifetime that led to its particular traits or behaviors.

ultimate cause

The reasons why, over many years of evolution, a particular trait or behavior helped members of a population to survive and reproduce.

natural selection

The mechanism that drives biological evolution. It refers to the greater likelihood of successful reproduction of organisms whose attributes are advantageous in a given environment.

naturalistic fallacy

The (mistaken) idea that anything "natural" must be "good."

mutations

Errors in the replication of DNA.

niche construction

The process in which organisms, through their own behaviors, alter the environment and create their own circumstances.

species specific

Pertaining to just one species.

species general

Pertaining to all organisms in a species.

dizygotic (DZ)

Twins that develop from two different eggs that are simultaneously fertilized by two sperm. Like ordinary siblings, they share 50% of their genes.

monozygotic (MZ)

Twins that develop from a single fertilized egg that then splits in half. These twins are genetically identical.

heritability ratio (H)

A measure that describes, for a given population in a given environment, what proportion of the variance of a trait is due to genetic differences.

environment of evolutionary adaptiveness (EEA)

The environment that was in place when a trait was evolving.

monogamy

A mating pattern in which one male and one female form an enduring reproductive partnership.

polygamy

Any mating system in which a member of one sex mates with several members of the opposite sex.

neuron

A specialized cell in the nervous system that accumulates and transmits information.

dentrites

The branched part of a neuron that receives impulses and conducts them toward the cell body.

cell body

The portion of the neuron containing the metabolic machinery that keeps the cell alive and functional.

axon

The part of the neuron that transmits impulses to glands, muscles, or other neurons.

efferent neurons

Nerves that carry messages outward from the central nervous system.

afferent neurons

Nerves that carry messages inward toward the central nervous system.

interneurons

Neurons that are neither afferent nor efferent, but instead carry information from one neuron to another.

glia

A type of cell in the nervous system long believed to provide a "support" function for neurons; recent research indicates that glia provide many other functions as well.

myelin

A fatty substance that makes up some types of glia cells; these cells wrap around the axon of some neurons, providing an insulating "myelin sheath" around these neurons.

action potential

A brief change in the electrical charge of a neuronal membrane; the physical basis of the signal that travels the length of the neuron.

resting potential

The voltage difference between the inside and the outside of a neuronal membrane when the neuron is not firing.

excitation threshold

The voltage difference between a neuron's interior and exterior that, if exceeded, causes the neuron to fire.

refractory period

The time after an action potential during which a neuron's cell membrane is unprepared for the next action potential.

depolarize

In the nervous system, to lose the charge that normally exists across the neuronal membrane.

propagation

The spread of the action potential down an axon, caused by successive changes in electrical charge along the length of the axon's membrane.

all-or-none law

The law that all action potentials have the same strength and speed regardless of the triggering stimulus.

synapse

The small group between two adjacent neurons, consisting of the presynaptic and postsynaptic neurons' membranes and the space between them.

neurotransmitters

Chemicals released by one neuron (usually the presynaptic neuron), which trigger a response in another neuron (usually the postsynaptic neuron); the chief means of communication among neurons.

synaptic reuptake

The presynaptic neuron's process of reabsorbing its own neurotransmitters after signaling so that they can be released again the next time the neuron fires.

agonists

Drugs that enhance a neurotransmitter's activity.

antagonists

Drugs that impede the activity of a neurotransmitter.

blood-brain barrier

Specialized membranes that surround the blood vessels within the brain and filter harmful chemicals out of the brain's blood supply.

endocrine system

The system of glands that release secretions directly into the bloodstream and affect organs elsewhere in the body.

hormone

A chemical released by a gland. Hormones travel through the bloodstream and influence functions such as metabolic rate, arousal level, and the liver's sugar output.

transcranial magnetic stimulation (TMS)

The technique of applying repeated magnetic stimulation at the surface of the skull to temporarily stimulate or disable a target brain region.

electroencephalogram (EEG)

A record of the brain's electrical activity recorded by placing electrodes on the scalp.

event-related potential (ERP)

Electrical changes in the brain that correspond to the brain's response to a specific event; measured with EEG.

CT (computerized tomography) scan

A technique for examining brain structure by constructing a composite of X-ray images taken from many different angles.

MRI (magnetic resonance imaging)

A neuroimaging technique that documents the effects of strong magnetic pulses on the molecules that male up brain tissue. A computer then assembles this information into a picture of a brain structure.

PET (positron emission tomorgraphy)

A technique for examining brain function by observing the amount of metabolic activity in different brain regions.

functional MRI (fMRI) scan

A technique for examining brain function by measuring blood flow and oxygen use within the brain.

central nervous system (CNS)

The brain and spinal cord.

peripheral nervous system (PNS)

The afferent and efferent nerves that extend from the brain and spinal cord to connect them with the organs and muscles.

somatic nervous system (SNS)

The division of the peripheral nervous system that receives information from and controls the internal organs.

autonomic nervous system (ANS)

The division of the peripheral nervous system that receives information from and controls the internal organs.

sympathetic branch

The division of the autonomic nervous system that mobilizes the organism for physical exertion.

parasympathetic branch

The division of the autonomic nervous system that restores the body's normal resting state and conserves energy.