Coloured and easy to remember notes on all the Research Methods sections of the AQA A Level Psychology (7181/7182) syllabus 2016 onwards specification . Includes all of AS content, with all of A Level and AS level content clearly marked.
, AQA A LEVEL Psychology topic companion: RESEARCH METHODS Page 3
EXPERIMENTAL METHODS
Specification: Experimental method. Types of experiment: laboratory and field
experiments; natural and quasi experiments.
WHAT YOU NEED TO KNOW
Outline and evaluate laboratory experiments.
Outline and evaluate field experiments.
Outline and evaluate natural experiments.
Outline and evaluate quasi experiments.
Introduction
Experimental methods all have one thing in common: they are attempting to find a cause and effect
relationship between an independent variable (IV) and dependent variable (DV), and to measure the
extent of this effect. There are four different types of experiment:
1. Laboratory experiment
2. Field experiment
3. Natural experiment
4. Quasi experiment
Summary of Experimental Methods
SETTING IV DV
LABORATORY Controlled conditions Manipulates the IV Measures the DV
FIELD Natural conditions Manipulates the IV Measures the DV
IV is naturally occurring
NATURAL Natural conditions (e.g. unemployment and an Measures the DV
earthquake)
IV is a difference between
Controlled conditions
QUASI people (e.g. gender and Measures the DV
/Natural conditions
age)
Laboratory Experiments
Laboratory experiments are conducted under specified controlled conditions in which the researcher
manipulates the independent variable (IV) to measure the effect on the dependent variable (DV). The
conditions are heavily controlled in order to minimise the effect of any extraneous variables, to prevent
them from becoming a confounding
variable which might adversely affect
the DV. Participants will be aware
that they are taking part in an
investigation due to the contrived
nature of the situation which may
feel unlike real‐life.
, Page 4 AQA A LEVEL Psychology topic companion: RESEARCH METHODS
Evaluating Laboratory Experiments
A strength of laboratory experiments is the high degree of control over extraneous variables which can
be achieved. A researcher is therefore able, in most cases, to prevent extraneous variables from
becoming confounding variables which negatively affect the DV. This provides a high degree of internal
validity allowing for conclusions about cause and effect to be drawn between the IV and DV.
A limitation of laboratory experiments is that they can lack external validity. The artificial nature of the
environment in which the investigation is taking place means that the study can lack ecological validity.
This means that the findings of the study cannot always be generalised to settings beyond the
laboratory as the tasks often lack mundane realism and would not be everyday life occurrences. Since
participants know they are being investigated their behaviour can also change in an unnatural manner
resulting in demand characteristics being seen.
Field Experiments
Field experiments are carried out in natural conditions, in which the researcher manipulates the
independent variable (IV) to measure the effect on the dependent variable (DV). The ‘field’ is considered
any location which is not a laboratory. Participants in a field experiment typically do not know that they are
taking part in an investigation with a view to observing more natural behaviour.
Evaluating Field Experiments
The natural setting means that field experiments often have a higher level of ecological validity, in
comparison to laboratory studies. This means that the results are more likely to be representative of
behaviour witnessed in everyday life. However, because the setting is more natural, there is less
control over extraneous variables. These can then become confounding variables and distort the
findings meaning a firm cause and effect relationship cannot be drawn since other factors could have
had an impact on the DV, other than the IV.
There are important ethical issues associated with field experiments. Since participants are often
unaware that they are in fact participants in a psychological investigation, they cannot give informed
consent to take part. As such, the research may involve a breach of their privacy rights and a cost‐
benefit analysis will need to be conducted before proceeding with any study to ensure the perceived
outcomes from the research will outweigh any personal costs to those involved.
Natural Experiments
In a natural experiment, the researcher does not manipulate the IV and instead examines the effect of an
existing IV on the dependent variable (DV). This IV is naturally occurring, such as a flood or earthquake,
and the behaviour of people affected is either compared to their own behaviour beforehand, when
possible, or with a control group who have not encountered the IV. It is important to note that it is the IV
which is natural in this type of experiment, and not necessarily the context in which the investigation is
taking place since participants could be tested in a laboratory as part of the study.
Evaluating Natural Experiments
The naturally occurring IV means that natural experiments often have a higher level of external validity
compared to laboratory and field experiments. These types of investigations are considered high in
ecological validity given the real‐life issues that are being studied rather than manipulated artificially.
However, natural experiments have no control over the environment and subsequent extraneous
variables, which means that it is difficult for the research to accurately assess the effects of the IV on
the DV. It may be that a confounding variable has affected the results so a cause and effect
relationship must be drawn with extreme caution, if at all.
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