Specification: Control: random allocation and counterbalancing, randomisation and standardisation. Demand characteristics and investigator effects.

Control

It is important that researchers know how to control/eliminate extraneous variables through the following measures: random allocation, counterbalancing, randomisation and standardisation.

Extraneous variables are any variable other than the IV that might affect the DV and thus affect the results.

Where extraneous variables are important enough to cause a change in the DV, they become confounding variables. There are many different types of extraneous variables that psychologists need to take account of when designing their investigations:

• Situational variables – variables connected with the research situation. For example, the temperature, time of day, lighting, materials, etc. They are controlled though standardisation, ensuring that the only thing which differs between the two groups is the IV. For example, making sure that the temperature is the same for both groups, the time of day is the same, etc.

• Participant variables – variables connected with the research participants. For example, age, intelligence, gender, etc. They are controlled through the experimental design, such as matched pairs design, or by randomly allocating participants to conditions, which helps to reduce bias.

Random allocation

Random allocation of participants to their groups, for example in an independent measures design, is an extremely important process in psychological research. Random allocation greatly decreases the possibility that participant variables in the form of individual differences, such as mathematical ability, will adversely affect the results.

Randomisation

This is when trials are presented in a random order to avoid any bias that the order of the trials might present.

Standardisation

This is the process in which all situational variables of a procedure used in research are kept identical, so that methods are sensitive to any change in performance. Under these circumstances changes in data can be attributed to the IV. In addition, it is far more likely that results will be replicated on subsequent occasions when research is standardised.

Demand characteristics and investigator effects

Both demand characteristics and investigator effects can act as confounding variables which affect the results of the research. Therefore, the researcher needs to exercise as much control over them as possible to maintain internal validity.

Demand characteristics occur when the participants try to make sense of the research and change their behaviour accordingly to support what they believe are the aims of the investigation. Demand characteristics are a problem as the participants act in a way to support the hypothesis rather than displaying natural behaviour, making the results lack validity. Conversely, the participant may deliberately try to disrupt the results, a phenomenon known as the ‘screw‐you’ effect.

Demand characteristics are controlled by not allowing the participants to guess the aim of the research or the identity of the IV which can be achieved by using a single‐blind experimental technique. This is when only the researcher knows the true aim of the experiment, and a measure of deception has been used so that the participants cannot easily guess the aim. Therefore, they are unable to try to either support or undermine the research on purpose. An example of this is in medical tests when comparing the effects of a therapeutic drug with a placebo, where only the researcher knows which is which.

Investigator effects are where a researcher (consciously or unconsciously) acts in a way to support their prediction. This can be a problem when observing events that can be interpreted in more than one way. For example, one researcher might interpret children fighting as an act of violence, while another might observe this as rough and tumble play. Investigator effects are best controlled by not allowing either the participants or the researcher (investigator) to know the aim of the research and/or identity of the IV. This is achieved by using a double-blind experimental technique. In this instance, only the person who originally designed the experiment knows the true aim, and a measure of deception has been used so that the participants and researcher are not aware. Therefore, either consciously or unconsciously, the investigator is unable to influence the participants. An example of this is in medical tests comparing the effectiveness of a therapeutic drug with a placebo, where neither the researcher nor the participants knows which is which. 

Possible exam questions

1. Explain what is meant by the term demand characteristics. (2 marks)

2. Define what is meant by random allocation. (2 marks)

3. Mary Ainsworth devised the Strange Situation methodology to observe caregiver–infant interactions. She classified the attachment type of the child through observing them in different situations with both their mother and a stranger.

Explain possible demand characteristics in Ainsworth’s research. (2 marks)

4. Suggest one way a researcher might try minimise the impact of demand characteristics. (2 marks)

5. Define what is meant by the term investigator effects, referring to a suitable example in your response. (2 marks)

6. Explain what is meant by counterbalancing in reference to psychological research. (3 marks)

7. Explain what a psychologist might do to ensure that their methodology follows standardised procedures. (3 marks)