,Experimental Methods Deciding which type of hypothesis to use
Key terms: • Psychologists tend to use a directional hypothesis when the findings of
• Experimental methods: Involves the manipulation previous research studies suggest a particular outcome. When there is no
of an independent variable to measure the effect previous research, or findings from earlier studies are contradictory, they will
on the dependent variable. Experiments may be instead decide to use a non-directional hypothesis.
laboratory, field, natural or quasi. • Even though SpeedUpp is a new energy drink, the effects of caffeine and sugar
• Aim: A general statement of what the researcher on talkativeness are well-documented. Therefore we will opt for a directional
intends to investigate; the purpose of the study. hypothesis on this occasion.
E.g. To investigate whether drinking energy drinks
makes people more talkative. Independent and dependent variables
• Hypothesis: A clear, precise, testable statement • In an experiment, a researcher changes or manipulates the independent
that states the relationship bet ween the variable (IV) and records or measures the effect of this change on the
variables to be investigated. Stated at the outset dependent variable (DV). All other variables that might potentially affect the
of any study. DV should remain constant in a properly run experiment. This is so the
• Directional hypothesis: States the direction of the researcher can be confident that the cause of the effect on the DV was the IV,
difference or relationship. E.g. People who drink and the IV alone.
SpeedUpp become more talkative than people who
don't. Levels of IV
• Non-directional hypothesis: Does not state the In order to test the effect of the IV we need different experimental conditions.
direction of the difference or relationship E.g. We need a comparison. We could either:
People who drink SpeedUpp differ in terms of • Compare participants' talkativeness before and after drinking SpeedUpp.
talkativeness compared with people who don't • Compare t wo groups of participants - those who drink SpeedUpp with those
drink SpeedUpp. who drink water
• Variables: Any 'thing' that can vary or change
within an investigation. Variables are generally In either case the t wo conditions are no SpeedUpp or drinking SpeedUpp. These are
used in experiments to determine if changes in one the t wo levels of the IV: the control condition (no SpeedUpp / drink of water) and
thing result in changes to another. the experimental condition (energy drink).
• Independent variable (IV): Some aspect of the
experimental situation that is manipulated by the Operationalisation of variables
researcher - or changes naturally - so the effect Many of the things that psychologists are interested in, such as social behaviour,
on the DV can be measured. intelligence or thinking, are often a little fuzzy and not easy to define. Thus, in
• Dependent variable (DV): The variable that is any study, one of the main tasks for the researcher is to ensure that the
measured by the researcher. Any effect on the DV variables being investigated are as unfuzzy and measurable as possible. So, a much
should be caused by the change in the IV. better hypothesis than the one above would be:
• Operationalisation: Clearly defining variables in • After drinking 300ml of SpeedUpp participants say more words in the next five
terms of how they can be measured minutes than participants who drink 300ml of water.
,Control of Variable Extraneous variables - explanation
The key to an experiment is that an independent variable (IV) is
Key terms: manipulated (changed) to see how this affects the dependent variable
• Extraneous variables (EV): Any variable, other (DV). The only thing that should influence the DV is the IV. Any other
than the independent variable (IV), that may variables that might potentially interfere with the IV (or the DV) should
have an effect on the dependent variable (DV) if be controlled or removed. These additional, unwanted variables are called
it is not controlled. EVs are essentially nuisance extraneous variables and, where possible, are identified at the start of
variables that do not vary systematically with the study by the researcher, who then takes steps to minimise their
the IV. influence.
• Confounding variables (CV): Any variable, other
than the IV, that may have affected the DV so we Many extraneous variables are straightfor ward to control such as the
cannot be sure of the true source of changes to age of the participants, the lighting in the lab, etc. These are described as
the DV. Confounding variables vary 'nuisance variables' that do not vary systematically with the IV. These
systematically with the IV. may 'muddy' the experimental water so to speak but do not confound the
• Demand characteristics: Any cue from the findings of the study. They may just make it harder to detect a result.
researcher or from the research situation that
may be interpreted by participants as revealing Confounding variables - explanation
the purpose of the investigation. This may lead to Confounding variables do change systematically with the IV. Let us
a participant changing their behaviour within imagine in our energy drink study we have t wenty participants in total
the research situation. and decide to use the first ten participants who arrive for the water
• Investigator effects: Any effect of the condition. It happens that these first ten participants are some very shy,
investigator's behaviour (conscious or introverted individuals. Our next ten participants, for the SpeedUpp
unconscious) on the research outcome (the DV). condition, are all quite extravert types, very loud and outgoing. An
This may include everything from the design of unfortunate coincidence you say but this coincidence means that we have
the study to the selection of, and interaction ended up with a second unintended IV - personality. So when we come to
with, participants during the research process. analyse our results and find that the Speedup group were chattier we
• Randomisation: The use of chance in order to can't be sure if this is because of the drink or the personalities of the
control for the effects of bias when designing participants.
materials and deciding the order of conditions.
• Standardisation: Using exactly the same Personality is a confounding variable. If our extravert types had been
formalised procedures and instructions for all spread evenly bet ween the t wo groups it wouldn't matter (though it
participants in a research study. might be worth controlling just in case). The problem was that
extraversion varied systematically with the IV and this alone could
explain changes in the DV.
, Demand Characteristics - explanation Randomisation - explanation
Participants are not passive within experiments and are likely to be In any investigation there are simple steps that the researcher can
spending much of their time trying to make sense of the new situation take to minimise the effect of extraneous/confounding variables on
they find themselves in. As such, participant reactivity is a significant the outcome. One of these is the use of randomisation, which refers
extraneous variable in experimental research and one that is very to the use of chance wherever possible to reduce the researcher's
difficult to control. influence on the design of the investigation. In short, this is an
attempt to control investigator effects.
In the research situation, participants will try to work out what is
going on. Certain clues may help them interpret what is going on. These For example, a memory experiment may involve participants
clues (or cues) are the demand characteristics of the experimental recalling words from a list. The order of the list should be randomly
situation and may help the participant to 's econd-guess' the generated so that the position of each word is not decided by the
experimenter's intentions as well as the aims of the study. experimenter.
Participants may also look for clues to tell them how they should In an experiment where participants are involved in a number of
behave in the experimental situation. They may act in a way that they different conditions, the order of these conditions should be
think is expected and over- perform to please the experimenter (the randomly determined. For example, in the energy drink experiment
'please-U effect'), or, they may deliberately under-perform to sabotage we might want to know what quantity of SpeedUpp caused
the results of the study (the 's crew-U effect'). Either way, participant chattiness, we may set up four experimental conditions: drinking
behaviour is no longer natural - an extraneous variable that may water (Condition A), drinking100ml of SpeedUpp (Condition B),
affect the DV drinking 200ml of SpeedUpp (Condition C), and drinking 300ml of
SpeedUpp SpeedUpp (Condition D).
Investigator effects - explanation
Participant reactivity also leads to investigator effects. Consider this: If all participants were to take part in all four conditions, the order
it is possible that during our energy drink study, as we are recording the in which these conditions were completed would need to be
words spoken by each participant, we may be inclined to smile more randomised for each participant
during our interactions with some participants than others. Given that
we are expecting the energy drink group to speak more than the water
group, we may unknowingly - in our unconscious behaviour - encourage Standardisation - explanation
a greater level of chattiness from the energy drink participants. As far as is possible within an investigation, all participants should
be subject to the same environment, information and experience. To
This is an example of an investigator effect, which refers to any ensure this, all procedures are standardised, in other words there is
unwanted influence of the investigator on the research outcome. As a list of exactly what will be done in the study. This includes
Hugh Coolican (2006) points out, this can include expectancy effects standardised instructions that are read to each participant. Such
and unconscious cues (such as those described above). It might also refer standardisation also means that non-standardised changes in
to any actions of the researcher that were related to the study's procedure do not act as extraneous variables.
design, such as the selection of the participants, the materials, the
instructions, etc.
Key terms: • Psychologists tend to use a directional hypothesis when the findings of
• Experimental methods: Involves the manipulation previous research studies suggest a particular outcome. When there is no
of an independent variable to measure the effect previous research, or findings from earlier studies are contradictory, they will
on the dependent variable. Experiments may be instead decide to use a non-directional hypothesis.
laboratory, field, natural or quasi. • Even though SpeedUpp is a new energy drink, the effects of caffeine and sugar
• Aim: A general statement of what the researcher on talkativeness are well-documented. Therefore we will opt for a directional
intends to investigate; the purpose of the study. hypothesis on this occasion.
E.g. To investigate whether drinking energy drinks
makes people more talkative. Independent and dependent variables
• Hypothesis: A clear, precise, testable statement • In an experiment, a researcher changes or manipulates the independent
that states the relationship bet ween the variable (IV) and records or measures the effect of this change on the
variables to be investigated. Stated at the outset dependent variable (DV). All other variables that might potentially affect the
of any study. DV should remain constant in a properly run experiment. This is so the
• Directional hypothesis: States the direction of the researcher can be confident that the cause of the effect on the DV was the IV,
difference or relationship. E.g. People who drink and the IV alone.
SpeedUpp become more talkative than people who
don't. Levels of IV
• Non-directional hypothesis: Does not state the In order to test the effect of the IV we need different experimental conditions.
direction of the difference or relationship E.g. We need a comparison. We could either:
People who drink SpeedUpp differ in terms of • Compare participants' talkativeness before and after drinking SpeedUpp.
talkativeness compared with people who don't • Compare t wo groups of participants - those who drink SpeedUpp with those
drink SpeedUpp. who drink water
• Variables: Any 'thing' that can vary or change
within an investigation. Variables are generally In either case the t wo conditions are no SpeedUpp or drinking SpeedUpp. These are
used in experiments to determine if changes in one the t wo levels of the IV: the control condition (no SpeedUpp / drink of water) and
thing result in changes to another. the experimental condition (energy drink).
• Independent variable (IV): Some aspect of the
experimental situation that is manipulated by the Operationalisation of variables
researcher - or changes naturally - so the effect Many of the things that psychologists are interested in, such as social behaviour,
on the DV can be measured. intelligence or thinking, are often a little fuzzy and not easy to define. Thus, in
• Dependent variable (DV): The variable that is any study, one of the main tasks for the researcher is to ensure that the
measured by the researcher. Any effect on the DV variables being investigated are as unfuzzy and measurable as possible. So, a much
should be caused by the change in the IV. better hypothesis than the one above would be:
• Operationalisation: Clearly defining variables in • After drinking 300ml of SpeedUpp participants say more words in the next five
terms of how they can be measured minutes than participants who drink 300ml of water.
,Control of Variable Extraneous variables - explanation
The key to an experiment is that an independent variable (IV) is
Key terms: manipulated (changed) to see how this affects the dependent variable
• Extraneous variables (EV): Any variable, other (DV). The only thing that should influence the DV is the IV. Any other
than the independent variable (IV), that may variables that might potentially interfere with the IV (or the DV) should
have an effect on the dependent variable (DV) if be controlled or removed. These additional, unwanted variables are called
it is not controlled. EVs are essentially nuisance extraneous variables and, where possible, are identified at the start of
variables that do not vary systematically with the study by the researcher, who then takes steps to minimise their
the IV. influence.
• Confounding variables (CV): Any variable, other
than the IV, that may have affected the DV so we Many extraneous variables are straightfor ward to control such as the
cannot be sure of the true source of changes to age of the participants, the lighting in the lab, etc. These are described as
the DV. Confounding variables vary 'nuisance variables' that do not vary systematically with the IV. These
systematically with the IV. may 'muddy' the experimental water so to speak but do not confound the
• Demand characteristics: Any cue from the findings of the study. They may just make it harder to detect a result.
researcher or from the research situation that
may be interpreted by participants as revealing Confounding variables - explanation
the purpose of the investigation. This may lead to Confounding variables do change systematically with the IV. Let us
a participant changing their behaviour within imagine in our energy drink study we have t wenty participants in total
the research situation. and decide to use the first ten participants who arrive for the water
• Investigator effects: Any effect of the condition. It happens that these first ten participants are some very shy,
investigator's behaviour (conscious or introverted individuals. Our next ten participants, for the SpeedUpp
unconscious) on the research outcome (the DV). condition, are all quite extravert types, very loud and outgoing. An
This may include everything from the design of unfortunate coincidence you say but this coincidence means that we have
the study to the selection of, and interaction ended up with a second unintended IV - personality. So when we come to
with, participants during the research process. analyse our results and find that the Speedup group were chattier we
• Randomisation: The use of chance in order to can't be sure if this is because of the drink or the personalities of the
control for the effects of bias when designing participants.
materials and deciding the order of conditions.
• Standardisation: Using exactly the same Personality is a confounding variable. If our extravert types had been
formalised procedures and instructions for all spread evenly bet ween the t wo groups it wouldn't matter (though it
participants in a research study. might be worth controlling just in case). The problem was that
extraversion varied systematically with the IV and this alone could
explain changes in the DV.
, Demand Characteristics - explanation Randomisation - explanation
Participants are not passive within experiments and are likely to be In any investigation there are simple steps that the researcher can
spending much of their time trying to make sense of the new situation take to minimise the effect of extraneous/confounding variables on
they find themselves in. As such, participant reactivity is a significant the outcome. One of these is the use of randomisation, which refers
extraneous variable in experimental research and one that is very to the use of chance wherever possible to reduce the researcher's
difficult to control. influence on the design of the investigation. In short, this is an
attempt to control investigator effects.
In the research situation, participants will try to work out what is
going on. Certain clues may help them interpret what is going on. These For example, a memory experiment may involve participants
clues (or cues) are the demand characteristics of the experimental recalling words from a list. The order of the list should be randomly
situation and may help the participant to 's econd-guess' the generated so that the position of each word is not decided by the
experimenter's intentions as well as the aims of the study. experimenter.
Participants may also look for clues to tell them how they should In an experiment where participants are involved in a number of
behave in the experimental situation. They may act in a way that they different conditions, the order of these conditions should be
think is expected and over- perform to please the experimenter (the randomly determined. For example, in the energy drink experiment
'please-U effect'), or, they may deliberately under-perform to sabotage we might want to know what quantity of SpeedUpp caused
the results of the study (the 's crew-U effect'). Either way, participant chattiness, we may set up four experimental conditions: drinking
behaviour is no longer natural - an extraneous variable that may water (Condition A), drinking100ml of SpeedUpp (Condition B),
affect the DV drinking 200ml of SpeedUpp (Condition C), and drinking 300ml of
SpeedUpp SpeedUpp (Condition D).
Investigator effects - explanation
Participant reactivity also leads to investigator effects. Consider this: If all participants were to take part in all four conditions, the order
it is possible that during our energy drink study, as we are recording the in which these conditions were completed would need to be
words spoken by each participant, we may be inclined to smile more randomised for each participant
during our interactions with some participants than others. Given that
we are expecting the energy drink group to speak more than the water
group, we may unknowingly - in our unconscious behaviour - encourage Standardisation - explanation
a greater level of chattiness from the energy drink participants. As far as is possible within an investigation, all participants should
be subject to the same environment, information and experience. To
This is an example of an investigator effect, which refers to any ensure this, all procedures are standardised, in other words there is
unwanted influence of the investigator on the research outcome. As a list of exactly what will be done in the study. This includes
Hugh Coolican (2006) points out, this can include expectancy effects standardised instructions that are read to each participant. Such
and unconscious cues (such as those described above). It might also refer standardisation also means that non-standardised changes in
to any actions of the researcher that were related to the study's procedure do not act as extraneous variables.
design, such as the selection of the participants, the materials, the
instructions, etc.
