In this first psychological research methods video, I’m going to discuss the different
types of experiments, so Lab, Field, Natural and Quazi, and discuss the strengths and weaknesses
of each.
If this is your first time coming to research methods, you're going to hear lots of terminology
you don’t know.
This can be a little intimidating, but the more you hear these words and their definitions,
the more confident you will get with research methods.
I’ve made these videos short, so you may want to watch them once, just listening without
taking notes, then again, pausing to write down the key ideas.
INTRO LABORATORY EXPERIMENTS: The first type a laboratory
or “lab” experiment is probably familiar to you.
A lab experiment could literally be set in a laboratory, but the important principle
here is the experimenter has full control over what happens in the experiment.
Environmental factors, like noise, temperature and even the instructions given to the participants
are all highly controlled and don’t vary between conditions, we call these factors
variables.
In a lab experiment the experimenter tries to make sure only one factor of the experiment,
called the independent variable changes between the conditions, all other variables are kept
the same.
This is so the experimenter can then measure how changing this independent variable changes
the variable measured known as the dependent variable.
For example, we may want to investigate how changing the colour of light in the room,
but not nothing else, influences the recall of numbers.
An advantage of using a lab experiment is by controlling for all other variables, you
can be confident in suggesting a cause and effect relationship.
Because you kept everything else constant, the variation you made to the independent
variable caused the change measured in the dependant variable.
This high control over the experiment means we would argue that lab experiments have high
internal validity, what they have measured is true.
The observed effect is real and is due to the change in the independent variable not
some other, uncontrolled factor.
Lab experiments are also highly replicable, you can give the instructions to another researcher,
so a list of standardised procedures for the participants and variables to keep the same.
Then if the researchers can conduct it in the same way and get the same results your
confidence in the validity of your findings increases.
However, there are disadvantages, Lab experiments may lack external validity, the laboratory
is not like the real world, and behaviours observed in lab conditions may not generalise
to environments outside of the lab, like the home, school or work this is known as lacking
ecological validity.
Also, the tasks used in an experiment are often unusual, not like tasks used in the
real world and so the behaviour may not be the same in real world, this is known as lacking
mundane realism.
Also being set in a lab, participants are aware they are in an experiment, they know
the experimenter wants to find something out, and are likely to change their behaviour to
match what they think is expected from them.
If this happens you would say your study suffers from demand characteristics.
Field: Field experiments attempt to fix some of the weaknesses of Lab studies.
So instead of being set in a lab they are conducted in the real world.
For example, the natural setting of a shopping centres, places or work or schools.
Places where people are used to behaving naturally.
Strengths of doing a field experiments are increased external validity, people would
be expected to show more naturalistic behaviour in their natural environment, so we can be
confident in generalising any behaviours measured to other situations, meaning higher ecological
validity.
Also, tasks used are more likely to be real world tasks, meaning increased mundane realism.
If the participants are unaware that they are taking part in a study, which is easier
in a field experiment, demand characteristics are also not a problem.
However, weaknesses of field experiments are due to the lack of control we had in the lab
experiment.
The real world is chaotic, and in a field experiment we are not able to control every
possible variable that may change your measurement of the dependent variable, these are known
as extraneous variables, and often in a field study researchers are not able to randomly
assign the participants to each condition.
This means that any effect observed may be due to a factor other than the change in the
independent variable.
This reduces the internal validity of the experiment.
Natural: In the previous two types of experiment the researcher manipulates the independent
variable themselves, and then records the change in the dependant variable.
However, in a natural experiment the levels of independent variable have already happened
naturally the researcher just measures the change in dependant variable.
So as an example, let’s imagine you wanted to study what would happen to children’s
development if you stopped them from getting any love and affection very early in life,
say you wanted to compare a group that had been deprived of love for less than six months,
a group between 6 months and two years and a group that had no emotional care for over
two years.
Then they are put with caring families.
Well of course you could never actually conduct this as a lab experiment for ethical reasons.
But this did happen to children in Romania in the 1980’s and a researcher called Rutter
followed these children up as they grew and recorded the effect of this deprivation on
their development.
Watch my video on the Romanian orphan studies if you want to know what Rutter found.
Strengths of natural experiments are they allow research in areas that could never be
done otherwise, either due to ethical reasons like Rutter, or cost.
Also, natural experiments are very high in external validity, these changes have happened
naturally in real life and would have happened with or without the researcher, so any changes
in behaviour can’t be the result of demand characteristics.
However, as the researcher has no control over the experiment, like randomising participants
to groups, or controlling for extraneous variables, there may be other factors that have influenced
the dependant variable, meaning we are not as sure of a cause and effect relationship
between the IV and DV as we are in a lab study.
Also because these situations occur naturally and are often rare, these studies can’t
be replicated to see if we get the same results.
Quasi the final type of experiment is known as a quasi-experiment, it has an unusual name,
but it’s simple.
In a true experiment you should be able to randomly assign participants to the different
levels of the independent variable.
So blue light or green light on recall.
But there are lots of studies we would like to conduct in which people can’t be randomly
assigned between conditions.
For example, if we are studying gender, or age or the differences between people with
or without a mental health condition.
These groups already exist and if we can’t as a researcher assign people to the different
conditions, or manipulate the levels of IV, that is a quasi-experiment.
A strength of this type of experiment is it's simply the only way to study these factors.
But a negative is there could be differences in these groups that goes beyond group membership.
Say for example if we are conducting a study on males and females, and looking at puzzle
solving.
There may be differences in how males and females have been educated and socialised
that explain the results.
These factors that change systematically between the conditions and can't be controlled are
known as confounding variables.
So that was types of experiments, I have 6 tutorial videos covering the 2017,18 and 19
AS and A-level research methods sections, these videos have worked examples to every
question and are full of exam tips.
Patrons at the neuron level and above can access these, and many, many more hours of
exam tutorial videos, as well as over a hundred printable resources from across the A-level
over on psych boost .com I do want to thank all the students and teachers
who have supported psych boost over on patreon during the development of the research methods
unit.
It's their support that allows me to teach part time so I can make psych boost on youtube
for everyone.
So thanks to them, and I will see you all in the next research methods video, observations.