Experimental Research Methods Flashcards
4 types of experimental research method
laboratory experiments
field experiments
natural experiments
quasi experiments
laboratory experiments
an experiment conducted in a laboratory under highly controlled conditions
all variables can be carefully controlled — the IV can be easily manipulated, the DV can be easily measured and EVs/CVs can be controlled
participants are aware they are taking part in an experiment but may not know the true aims of the study
it is the participant’s awareness of being in a study that contributes to the contrived nature of lab studies as participants may alter their behaviour because they know its being recorded
involve artificial materials and tasks (e.g. consonant syllables used in Peterson and Peterson’s study of STM or film clips used to test EWT in Loftus and Palmer’s study) which makes the experience less like everyday life and does not represent everyday experiences — low ecological validity, lacks mundane realism
field experiments
an experiment conducted in everyday/real life environments of the participants — outside a laboratory
the experimenter deliberately manipulates the IV and measures the DV
participants are usually not aware that they are participating in an experiment, so their behaviour tends to be more natural
natural experiments
an experiment conducted in the everyday/real life experiments of the participants
the experimenter has no control over the variables; the IV varies naturally and has not been manipulated, although the DV can be tested in a laboratory
conducted when it’s not possible, for ethical or practical reasons, to deliberately manipulate the IV (e.g. depression, smoking)
EXAMPLE = in Rutter’s study, the effects of institutionalisation on the subsequent emotional and intellectual development of Romanian orphans was studied, the IV in this study was adoption either before or after the age of 6 months, it would not be ethical to deliberately control this IV by deciding that some babies would be adopted early but others would have to wait, so the IV occurred naturally and wasn’t manipulated
quasi experiments
an experiment in which participants are not randomly assigned to experimental groups because the experimenter is interested in an IV that cannot be assigned randomly as it is simply a difference/characteristic between people that exists
e.g. personality traits, gender, locus of control, age
the IV occurs naturally and has not been manipulated but DV can be measured in a lab
conducted when it’s not possible to deliberately manipulate the IV
EXAMPLE = Sheridan et al (1972) tested obedience by asking male participants to give electric shocks or increasing strength to a poppy, 54% or male participants delivered the maximum shock but 100% of women delivered the maximum shock, the IV here was gender, a difference that cannot be manipulated
advantages of laboratory experiments
- easy to replicate and repeat in order to get reliable results
- high internal validity — variables can be controlled and monitored very precisely, therefore we can be more certain that any observed change in the DV is due to the IV
- dependent variable can be measured accurately
- extraneous variable can be controlled and reduces the likeliness they’ll interfere with results
disadvantages of laboratory experiments
- low ecological validity — participants are aware they’re being studied, tasks tend to be more artificial and the overall artificial setting of a laboratory may result in unnatural behaviour and demand characteristics that don’t reflect real life behaviour so results may be hard to generalise to real life and may not be entirely accurate
- experimenter bias may interfere with results, investigator may give clues as to the research aims, etc
- possibly unethical due to deception or lack of informed consent
- can only use small samples, very hard to test across cultures and countries and can take a lot longer to gain a good amount of results
advantages of field experiments
- less likely for demand characteristics to be an issue as participants are less likely to behave a certain way due to natural surroundings — behaviour is more reflective of real life, especially if the participants do not know they’re being studied which is usually the case
- high ecological validity — higher level of mundane realism because the study takes place in a more natural environment, therefore findings are easier to generalise
- can use a much larger sample so results can be more easy to generalise and more representative of the whole population
disadvantages of field experiments
- lower internal validity — not all variables can be easily controlled, extraneous variables can be difficult to control and confounding variables may interfere and ruin results
- IV can still lack mundane realism — field studies are not necessarily more like everyday life than lab studies
- harder to replicate and repeat experiment in the same way to ensure reliability of results
- ethical issues — if they’re unaware they’re being studied, this may lead to issues of deception and lack of informed consent, there may be ethical issues with manipulating and recording behaviour without them knowing
- more time consuming and thus more expensive
advantages of natural experiments
- behaviour is more likely to be reflective of real life so results may be more valid and accurate - high ecological validity
- less likely for demand characteristics to be an issue if participants don’t know they’re being studied
- eliminates experimenter bias as iv is not being controlled
- can be used in situations where it would be unethical or impractical to manipulate the iv (for example, if it was anxiety), thus allowing research where the IV would not otherwise be able to be manipulated — links to the idea that these experiments enable psychologists to study real problems such as the effects of disaster on health
disadvantages of natural experiments
- more expensive and time consuming as experimenter doesn’t control the iv, it’s just there
- not a true experiment — the IV is not deliberately manipulated, meaning it is not possible to claim that changes in the DV are caused by the IV, causal conclusions cannot be drawn, they can only be drawn tentatively e.g. Romanian orphans study
- extraneous and confounding variables have a high chance of interfering with results as they are hard to control, especially because random allocation is not possible — low internal validity
- difficult to replicate and repeat to ensure reliability of results
advantages of quasi experiments
- more genuine and natural behaviour that’s reflective of real life when put in natural settings
- reduces ethical issues regarding the manipulation of iv as in this case, it’s not able to be randomly assigned
- useful when it’s otherwise unethical or not possible to manipulate iv
- allows researchers to study differences and comparisons between types of people
disadvantages of quasi experiments
- participants are not randomly assigned and this could lead to inequivalent/unrepresentative groups as well as experimenter bias
- extraneous and confounding variables have a high chance of interfering with results as they are hard to control, especially because random allocation is not possible — low internal validity
- iv is not manipulated, it simply exists. makes it more expensive and time consuming as experimenter doesn’t control the iv, it’s just there
- not a true experiment — the IV is not deliberately manipulated, meaning it is not possible to claim that changes in the DV are caused by the IV, causal conclusions cannot be drawn, they can only be drawn tentatively e.g. Sheridan et al (1972) cannot be certain that being female caused the participants to shock the puppies, it is only a correlation OR in studies with age differences, it is not necessarily age that has caused the behaviour, it may actually be characteristics that vary with age such as dementia
- participants may be aware they’re being studied, thus reducing internal validity
- DV may be a fairly artificial task, reducing ecological validity
why can’t researchers draw cause and effect conclusions from natural and quasi experiments?
MANIPULATION OF IV — lack of control over IV means we cannot say for certain that any change in the DV was caused by the IV, if there were uncontrolled confounding variables then observed changes in the DV may not be due to the IV
RANDOM ALLOCATION — participants cannot be randomly allocated to conditions in natural and quasi experiments, meaning there may be biases in different groups of participants and uncontrolled confounding variables, for instance in the study on institutionalisation there may be other variables that were not controlled such as friendliness of the child, it may be that more sociable children were adopted early, leaving naturally less sociable children in institutions and assuming this is an effect of institutionalisation when it may not be
UNIQUE CHARACTERISTICS OF PPTS — the sample studied may have unique characteristics, for example in the St Helena study the people were part of a particularly helpful and pro social community which might explain why violence on TV did not affect their behaviour, therefore findings cannot be generalised to other groups of people as the sample may be unique and not representative of the general population, the study has low population validity
