Research Methods in Psychology

Case study method is used to get a detailed picture of one participant or a small group of participants
Clinical psychologists use case studies to present information about a person suffering from a particular disorder
However, the findings cannot be applied to a larger population due to the focus on a small group of participants

Descriptive statistics describe a set of data
Frequency distribution is a set of data represented as numbers
Frequency polygon is a line graph, while histogram is a bar graph
Central tendency marks the center of distribution using mean, median, and mode
A distribution can be bimodal, meaning two scores appear equally frequently and more frequent than any other score
Extreme scores or outliers can distort the mean, making the median a better measure of central tendency in such cases
Positively skewed distributions occur when the skew is caused by a particularly high score, while negatively skewed distributions occur when the skew is caused by a particularly low score
Measures of variability include range, variance, and standard deviation, which attempt to depict the diversity of the distribution
Range is the distance between the highest and lowest score in a distribution
Variance and standard deviation are closely related, with standard deviation being the square root of the variance
The higher the variance and standard deviation, the more spread out the distribution
Z scores measure the distance of a score from the mean in units of standard deviation, with scores below the mean being negative and scores above being positive
Percentile indicates the distance of a score from 0

In its resting state, a neuron has an over-negative charge
The cell membrane is selectively permeable and prevents ions from mixing
The reaction begins when the terminal buttons of the first neuron are stimulated and release neurotransmitters into the synapse
These neurotransmitters fit into receptor sites on the dendrites of the second neuron
If enough neurotransmitters are received, positive ions rush into the cell and travel down the neuron like a bullet from a gun
This firing is called the action potential
A neuron needs to receive enough neurotransmitters to pass its threshold to make it fire
A neuron cannot fire a little or a lot, it's the same every time, which is called the all-or-none principle

Some neurotransmitters are excitatory, meaning they excite the next cell into firing
Others are inhibitory, meaning they inhibit the next cell into firing
Each synaptic gap may contain different kinds of neurotransmitters
The amount and types of neurotransmitters received on the receptor sites determine whether or not it will pass the threshold and fire
Acetylcholine is involved in motor movement and its lack is associated with Alzheimer's disease
Dopamine is involved in motor movement and alertness, and its lack is associated with Parkinson's disease, while its excess is associated with schizophrenia

Adrenal glands produce adrenaline, which signals the rest of the body to prepare for fight or flight
Ovaries and testes produce sex hormones, estrogen for women and testosterone for men
Levels of these hormones in men and women may partially explain gender differences

Most human traits result from the combined effects of nature (our genetic code) and nurture (the environment where we grow up and live)
Every human cell contains 46 chromosomes in 23 pairs
Chromosomes are made up of DNA (deoxyribonucleic acid)
Segments of DNA produce specific proteins that control some human traits
These are called genes, which can be dominant or recessive
Identical twins share the same genetic material, and researchers study their traits to determine how much of an impact genes have on these traits
Effective psychological environment refers to when a pair of twins grows up in similar environments, causing them to have alike traits
Chromosomal abnormalities can occur, resulting in mental retardation, with Down syndrome being the most common type

Transduction is the process of a signal being transformed into neural impulses
Sensory adaptation refers to decreasing responsiveness to stimuli due to constant stimulation
Sensory habituation refers to the fact that our perception of sensation is partially due to how focused we are on them
Deafness can be caused by conduction deafness or nerve deafness, with nerve deafness being more difficult to treat
The gate-control theory explains that pain messages have a higher priority than others
Endorphins can also affect the gate, releasing it when they are released into the body

Taste (gustation) involves the absorption of chemicals by taste buds, which are located on the papillae
Humans sense five types of tastes: sweet, salty, sour, bitter, and umami (savory)
Smell (olfaction) depends on the chemicals emitted by substances
Researchers estimate that 100 different types of smell receptors may exist
These receptors are linked to the olfactory bulb, which sends this information to the brain

The vestibular sense tells us how our body is oriented in space using the semicircular canals in the inner ear
The kinesthetic sense tells us the position and orientation of specific body parts using receptors in muscles and joints

Signal detection theory investigates the effect of distractions and interference on perception
Response criteria refer to how motivated we are to detect certain stimuli and what we expect to perceive
False positives occur when we think we perceive a stimulus that is not there, while false negatives occur when we do not perceive a stimulus that is present
Top-down processing involves using background knowledge to fill in gaps in perception
Bottom-up processing is the opposite, using features of an object to build a complete perception
Feature detectors allow our mind to build a picture using basic characteristics
Principles of visual perception include the figure-ground relationship, which determines what part of the image is the figure and what part is the background
Gestalt rules state that we normally perceive images as groups, not as isolated elements, and are influenced by factors such as proximity, similarity, continuity, and closure
Constancy refers to our ability to maintain a constant perception of an object despite changes