Week 3 - Research Methods Flashcards
Experimental research design
Independent variable - variable that is manipulate in a study
Dependent variable - variable that is measured in a study
Experimental control
Experimental between-subjects design
experiments are conducted with 2 or more different groups
- interested in the difference between the means of these groups
example: group A given a new drug; group B given CBT
Advantages of between groups
- easier and more time efficient to run
- allows observation of variables that are not stable
Disadvantages of between groups
- many variables are unable to be controlled
- results are presented in terms of group differences; masks changes within the individual
- method of allocating to groups
Experimental within-subjects design
repeated measures
same participants involved in every level of the experiment
- usually interested in difference in the mean of the 2+ testing occassions
eg. participants tested for attention span before & after taking drug
Advantages of repeated measures
- requires fewer participants
- each participant acts as their own control
Disadvantages of repeated measures
- not amenable to measurement of unstable variables
- time & money
- may need alternate forms to assess DV to counteract practice effect
- may need to counteract cross-over effects
Placebo controls
a placebo control condition will be similar to the experimental condition, except rather than receiving the drug they receive a substance containing no active ingredients
- placebo controls are extremely useful for investigating whether any benefits derived from a drug are due to placebo effects
Three-groups design
- given a new drug
- given a proven drug
- given a placebo
Control groups/conditions
- used to ensure the effect observed is due to the variable we manipulated & not some other variable
- especially important in between-subjects designs
- control group will be identical to the groups being tested, except for the manipulation
what do three-groups designs allow for
- comparison between new drug & placebo
- comparison between new & established drugs
- experimenter to see if measure are sensitive enough to detect change
what are the alternate combinations of groups that could be used to answer alternate questions
- effectiveness of drugs vs non-pharmacological interventions
- specificity of drug effectson different mental illnesses
- cross-sectional and longitudinal
Sources of bias
- systematic errors in measurement or prediction
- experimenter and participant expectations/bias
- selection bias
Research methods
- introspection
- naturalistic observation
- case history
- survey
- test
- correlation
- experiment
Potential variables
- arousal
- cognition
- perception
- motor function
- mood
- side effect/biochemical or physiological drug effect
The more measures used creates
- a more comprehensive assessment
- a more costly experiment
- a greater need to consider ecperimental controls & logistics
Measuring performance
assessing change/differences in performance across performance domains (arousal, cognition etc) tells us something about how the drug works, and the effects it produces
Arousal levels
- arousal levels change naturally throughout the day, but can also be affected by a number of things.
- drugs are thought of as either stimulants or depressants when given in large doses.
- uppers and downers imply a relationship between arousal and mood
- high arousal does not equal high activity
Measuring arousal
- EEG
- introspection; unstructured introspection, systematic introspection
- ask an observer
Levels of arousal
- death
- coma
**- sleep - drowsy
- normal
- aroused
- highly excited**
- mania
- convulsions
- death
** = normal range of arousal
Measures of mood
Studied: experimentally or between groups design
Measured: self-report, doctor’s assessment, informant report, questionnaire, tests of biological markers of depression
Measures of perception
visual and auditory perception are most often studied, and is investigated by the changes in the sensitivity of a person’s perception brought about by changes in the internal or external environment
Sensitivity thresholds
- absolute threshold - lowest value of stimulus detactable by an organ
- difference threshold - organ detects a change in level of stimulation
Absolute thresholds detected 50% of the time
vision: candle flame on a dark straight road at 60km/h
smell: 1 drop of perfume in a 6 room apartment
hearing: watch tick 6m away
taste: 1tsp sugar in 8L water
touch: wing of a fly falling on your cheek from 1cm
Difference thresholds
measure the ability of an individual to detect a change in a stimulus
- critical frequency at fusion (CFF) sensitive to drug effects
Cognitive performance
ability to process, store and retrieve information; can also include higher-level processes such as planning, set-shifting & response inhibition
how is cognitive performance manipulated?
experimentally
measuring motor performance
- simple or choice reaction time
- tapping
- pursuit rotor
measuring side effects/physiological effects
- questionnaire
- biochemical assay
- doctor’s checkup/physical exam
- informant report
general questions of identifying good research design
- what is the research question: does the chosen design allow that question to be answered
- what are the strengths and limitations of the measures used to assess effects
- what experimental controls have been put in place
- effect size: how meaningful is the change observed in terms of everyday functioning?
factors to consider with drug studies
- washout effect
- deprivation study designs
- level of drug administered
- dose of drug used
- inclusion of biochemical assays
- controls for routine/habitual or other drug use
- non-specific treatment effects
- special group selection factors (mild, moderate, sever depression)
- timeframe for assessing effect
- reporting of adverse events/non-compliance/attrition
factors to consider with drug studies cont.
- if in-vitro cellular trials are used: how generalisable are results to intact living systems?
- if animal trials are used: how similar is the species, apparatus, domain of function being tested
Research ethics
- APS code of ethis
- NHMRC guidelines
drug development
- development, testing, manufacturing & eventual marketing of any drug is time-consuming & expensive
- companies can evaluate 1000s of different chemicals before finding one that is successful in all phases of testing
Major considerations in drug development
- medical need
- commercial potential
- feasibility for mass production
“orphan drugs”
FDA approval processes
- preclinical investigation (animal studies)
- clinical investigation (human volunteers)
- review of NDA
- postmarketing studies
Specifc limitations of animal studies
cats: markedly different sleep-wake cycles
monkeys: develop obvious behavioural abnormalities from confinement
rabbits: different enzymes from humans
Stage 1: step 1 of animal testing
Determing toxicity
- acute toxicity (for single doses)
- subacute toxicity (short-term use of drug)
- chronic toxicity (longer-term drug use)
- special toxicity (carcinogenic, teratogenic)
Stage 1: step 2 of animal testing
pharmacological studies (direct and indirect)
direct: to locate direct measures of changes induced by drugs via tools
indirect: to identify markers of signs of effect rather than evidence of the effect itself or to observe effects on behaviours that are induced in animals
Direct pharmacological studies - conditioning: General principles
Stimulant substances: rapid learning/acquisition of conditioned response, poor discrimination/ready generalisation, slow termination/extinction
Depressant substance: slow acquisition/learning, poor generalisation/easy discrimination, rapid extinction
Schedules of reinforcement
pattern that determines when reinforcements are to be given
- ratio schedules
- interval schedules
- avoidance-escape take
- punishment
Stimulus properties of drugs
ability to act as a discriminative stimulus in discrimination learning taks
Reinforcing properties of drugs
- rate of responding
- progressive ratio - breaking point
- choice - 2 levers; one has consequences
- conditioned place preference - animal will spend time in area of reinforcement
Phase 1 of human testing
pharmacokinetic & safety testing
human testing to determine toxicity & side effects in healthy human volunteers
Phase 2 of human testing
small scale and effectiveness testing
human testing in clinical samples to assess potential therapeutic effect (adverse)
Phase 3 of human testing
large scale effectiveness testing
expanded clinical trials using basic 3-group design
(approval or rejection of new drug for licensing & marketing
Phase 4 of human testing
accumulation of data on drug effects
Postmarketing studies
phase 4
- after NDA review completed & approved
- lasts on average, 15 years
- new drug placed on the market
- surveillance: check for new harmful effects in larger group of humans
- drug removed from market if seroius problems occur
