Types of Experiment (AQA AS Psychology)

Laboratory experiments

• A lab experiment is a type of research method in which the researcher can exert high levels of control over what happens as part of the experimental process

• The researcher controls the environmental factors, such as noise and temperature (possible extraneous variables) so that the effects of the independent variable (IV) upon the dependent variable (DV) can be observed and measured

• Lab experiments use a  standardised procedure to ensure replicability and reliability

• All variables are kept the same/constant: only the independent variable changes between conditions

  • the experiment is run in the same room/space per condition

  • the light, heat, sound levels are kept constant per condition

  • the researcher treats the participants in the same way (e.g. tone of voice, body language, clothing) per condition

• Keeping all variables constant means that the DV can be measured exactly using quantitative data

Evaluation of lab experiments

Strengths

• It is easier to establish a cause-effect relationship between the IV and the DV than for other methods used in psychology

  • This is due to the use of controls and the objective nature of the research

  • Therefore lab experiments are high in internal validity

• The use of a standardised procedure means that the research is replicable which increases the reliability

Limitations

• The use of artificial tasks means that lab experiments lack ecological validity

  • If participants are performing tasks in an unfamiliar, 'sterile' setting this does not reflect how they might behave in real conditions

  • This makes the findings difficult to generalise beyond the lab setting

• Demand characteristics may limit the generalisability of the findings

  • As participants know they are in a study they may alter their behaviour (e.g. they may feel shy, self-conscious or they may try too hard)

  • This would lower the external validity of the study

Field experiments

• A field experiment is a research method which takes place in a natural setting, away from the lab

• The researcher has less control over what happens as part of the experimental process due to the use of a real-world location

• The researcher can control the environment to some extent but they have to acknowledge the fact that many extraneous variables are part of field experiments e.g.

  • if the experiment takes place outdoors the weather will be a factor (e.g. people's mood lifts in the sun and is less positive in the rain)

  • if the experiment takes place in a crowded environment there is the distraction of other people, noise, traffic, shops etc.

• Field experiments are not the same as naturalistic observations: they still involve the implementation of an IV and DV e.g.

  • a confederate of the researcher pretends to collapse on a subway train

    • The IV is whether the victim appears to be drunk or disabled

    • The DV is the number of people who go to the victim’s aid

  • a researcher implements a ‘Kindness’ programme with half of the Year 5 students in a primary school

    • The IV is whether the students have followed the ‘Kindness’ programme or not

    • The DV is the score they achieve on a questionnaire about prosocial behaviour after one month

• Field experiments collect quantitative data but there is also more possibility for researchers to obtain qualitative data as part of the research process,e.g.

  • interviews with passengers who witnessed the ‘victim’ collapsing on the train

  • teachers’ observations of behavioural differences in the ‘Kindness’ programme children across the month of the study

• Any qualitative data collected could be used to comment on the quantitative findings and shed light on the actions of the participants

Evaluation of field experiments

Strengths

• As the research is conducted in real settings the degree of artificiality is reduced

  • If participants feel more comfortable in the setting this means that their behaviour is likely to reflect their behaviour outside of the research parameters

  • This makes field experiments high in external validity

• Participants are less likely to experience demand characteristics due to the more relaxed and 'natural' environment of a field experiment which heightens the validity of the findings

Limitations

• Extraneous variables are much more likely to interfere with the findings of the study

  • The researcher cannot control all extraneous variables due to the lessening of control possible with field experiments

  • This means that reliability is reduced

• It is more difficult to replicate field experiments due to the nature of the method

  • This in turn reduces the ability to check for consistency - and hence reliability - of the results

Natural experiments

• Natural experiments consist of research in naturally occurring phenomena, e.g.

  • the researcher cannot manipulate the IV

  • the researcher cannot randomly allocate participants to condition (due to the naturally-occurring IV)

  • the research takes place in the participant's natural setting

  • the researcher observes, measures and records the natural changes and responses which have occurred due to the naturally occurring phenomena

• Naturally occurring phenomena which might be used as the basis for a natural experiment include

  • living in a war zone

  • suffering from a specific mental illness

  • surviving a plane crash

• Often naturally occurring phenomena would be highly unethical for a researcher to impose on participants, hence they look for people who have experienced/are experiencing the specific phenomenon

• The IV in a natural experiment is naturally-occurring

  • The researcher determines the DV and then designs their research to investigate the effects of the IV on the participants

• Natural experiments may be conducted in real-world settings e.g.

  • the effects of having lived through a natural disaster such as a hurricane on stress levels

  • the effects of caring for someone with dementia

• The researcher may collect data using interviews

  • In this way, natural experiments are very different to lab, field or quasi-experiments as they are likely to collect qualitative data

Evaluation of natural experiments

Strengths

• They allow the researcher to investigate topics which would otherwise be unethical to study using a traditional lab experiment e.g. experiencing a mental illness or a natural disaster

  • This means that natural experiments are high in ethical validity

• Natural experiments are high in ecological validity

  • The participants report on events and experiences that they have personal, first-hand knowledge of

  • The researcher does not attempt to control the procedure

  • This elevates mundane realism

Limitations

• Causal relationships are difficult to determine due to the array of variables at play

  • This is a key limitation of research which imposes no controls on the procedure

  • The researcher cannot be sure as to what effect the phenomena have had on the participants - they have to rely on the accounts of the participants themselves

  • This reduces the reliability of natural experiments

• Natural experiments may suffer from several types of bias which would lower the validity of the study e.g.

  • social desirability bias

    • The participant wishes to present themselves and their experiences in the best light possible

  • confirmation bias

    • The researcher looks for evidence that will back up any pre-existing ideas they have brought to the research process

  • sample bias

    • The sample is determined by experience which means that only a very limited group of people can be used in the research

Quasi experiments

• A quasi-experiment is a research method which does not manipulate the IV; similar to a natural experiment it uses naturally occurring phenomena e.g.

  • age

    • an experiment in which digit-span recall is tested between a group of young people compared to a group of older people

  • gender

    • the performance of girls is compared to the performance of boys in an experiment testing emotional intelligence

  • experience

    • a group of teachers from one school who have been trained in empathy are compared to a group of teachers from another school who have not had this training on an emotion-recognition task

• The researcher has less control over what happens as part of the experimental process as they cannot randomly allocate participants to condition

  • the participants are the conditions of the IV e.g.

    • either young/old, female/male, trained/untrained

• Quasi experiments collect quantitative data as they can be run in the same way as a 'true' lab experiment

  • the only variable which cannot be controlled by the researcher is the IV

Evaluation of quasi experiments

Strengths

• Due to the lack of manipulation of the IV the results could be said to be higher in external validity

  • Comparing the performance of young versus older people on a memory test gives insight into the effect of age on recall

  • Comparing the ability to identify emotion based on empathy training gives insight as to how this training might benefit other groups or professions

• Quasi-experiments follow a true experimental design which means that they could be replicated with participants that match the original sample in terms of demographics e.g.

  • The effect of age on recall could use the same procedure over and over again

Limitations

• As the participants cannot be randomly allocated to condition this can lead to participant variables, making it difficult to determine causality

  • A study which investigates the effect of age on recall might include a group of participants (in either the younger or the older group) who naturally have a much better memory than is representative of their population

  • This means that quasi-experiments are less reliable than true experiments

• Quasi-experiments lack internal validity, as there may be other factors which could explain the results

  • The teachers who have been trained in empathy may work in a school in which emotional intelligence is valued

  • This means that they would already be at an advantage in an emotion-recognition task