Psychology research methods

• Types of experiment


  • Laboratory experiment
  • Field experiment
  • Natural experiment
  • Quasi experiment
• Experimental methods


  • 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
• Laboratory experiment


  Conducted under specified controlled conditions in which the researcher manipulates the independent variable (IV) to measure the effect on the dependent variable (DV)
• Laboratory experiments


  • Conditions are heavily controlled in order to minimise the effect of any extraneous variables
  • Participants will be aware that they are taking part in an investigation due to the contrived nature of the situation
• A strength of laboratory experiments

  High degree of control over extraneous variables which can be achieved, providing 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

  Can lack external validity as the artificial nature of the environment means the study can lack ecological validity, and findings cannot always be generalised to settings beyond the laboratory
• Field experiment


  Carried out in natural conditions, in which the researcher manipulates the independent variable (IV) to measure the effect on the dependent variable (DV)
• A strength of field experiments

  The natural setting means they often have a higher level of ecological validity, in comparison to laboratory studies, making the results more likely to be representative of behaviour witnessed in everyday life
• A limitation of field experiments

  Less control over extraneous variables, which can then become confounding variables and distort the findings, making it difficult to draw a firm cause and effect relationship
• Ethical issues with field experiments

  Participants are often unaware that they are in fact participants in a psychological investigation, so cannot give informed consent
• Natural experiment


  The researcher does not manipulate the IV and instead examines the effect of an existing IV on the dependent variable (DV), where the IV is naturally occurring
• A strength of natural experiments

  Often have a higher level of external validity compared to laboratory and field experiments, and are considered high in ecological validity given the real-life issues being studied
• A limitation of natural experiments

  No control over the environment and subsequent extraneous variables, making it difficult to accurately assess the effects of the IV on the DV
• Quasi experiment


  Contains a naturally occurring independent variable (IV), but one which already exists as a difference between people such as gender, age or a personality trait
• A limitation of quasi experiments

  Participants cannot be randomly allocated to research conditions to remove the issue of bias in the procedure, so the psychologist will be less certain that the IV alone will have caused the effect
• Methodological issues with quasi experiments

  When under natural conditions, no control over the environment and extraneous variables; when under laboratory conditions, high control but lack of ecological validity
• Comparison of experimental methods

  • Ecological validity
  • Extraneous variables
  • Replicability
• The level of each factor in the comparison depends on whether the quasi experiments are carried out in a laboratory setting or under natural conditions
• the research often lacks ecological validity, and the findings cannot always be generalised to a real‐life setting since behaviour may not translate outside of the research environment
• Comparison of Experimental Methods

  • ECOLOGICAL VALIDITY
  • EXTRANEOUS VARIABLES
  • REPLICABILITY
• Experimental Methods


  • LABORATORY
  • FIELD
  • NATURAL
  • QUASI
• LABORATORY


  • Low ecological validity
  • Controlled
  • High replicability
• FIELD


  • High ecological validity
  • Not controlled
  • Low replicability
• NATURAL


  • High ecological validity
  • Not controlled
  • Low replicability
• QUASI


  • Low/High ecological validity
  • Controlled/Not controlled
  • High/Low replicability
• The level of each factor depends on whether the quasi experiments are carried out in a laboratory setting or under natural conditions
• Experiment conducted by Dr Helpful

  1. Participants randomly allocated to two groups

  2. Group 1 heard three strengths of Ms B's CV followed by three negative comments

  3. Group 2 heard three negative comments about Ms B's CV followed by three strengths

  4. Participants stated whether they thought Ms B would be a competent colleague
• Quasi experiment


  An experiment where the independent variable is not manipulated by the researcher, but rather occurs naturally or is selected based on pre-existing differences between participants
• Features of an experiment

  • Manipulation of the independent variable
  • Measurement of the dependent variable
• Laboratory experiment


  An experiment conducted in a controlled environment, usually a laboratory, where the researcher has a high degree of control over extraneous variables
• Laboratory experiment vs Field experiment

  Laboratory experiments have lower ecological validity but higher control over extraneous variables, while field experiments have higher ecological validity but lower control over extraneous variables
• The study on phobias and heartbeat awareness is considered a quasi experiment because phobias are pre-existing (evolutionary/biological origin) or naturally occurring (learned from the environment)
• Natural experiment vs Field experiment

  Natural experiments occur in the real world without the researcher manipulating the independent variable, while field experiments are conducted in a natural setting but the researcher does manipulate the independent variable
• The researchers decided to use a field experiment rather than a laboratory experiment to study people's memory of Donald's face because it allowed for higher ecological validity and fewer demand characteristics
• Extraneous variable


  A variable that is not manipulated by the experimenter but may have an effect on the dependent variable, making it difficult to establish a cause and effect relationship
• Controlling extraneous variables is important in experimental research to avoid confounding the results and making it difficult to establish a causal relationship between the independent and dependent variables
• Advantages of conducting the caffeine and memory experiment in a laboratory

  • Higher control over extraneous variables like strength of caffeinated drink
  • Ability to ensure standardized procedures
  • Reduced risk of external distractions or interruptions
  • Increased replicability of the study
• Laboratory experiments allow for high control over extraneous variables, but have lower ecological validity compared to field experiments
• Overt observation


  Participant is aware
• Overt observation


  • More ethical: informed consent obtained
  • Investigator effects and demand characteristics are more likely