What causes the placebo effect?

Although there is no definite answer to what causes the placebo effect, researchers propose a number of explanations such as the power of suggestion, doctor-patient interaction, classical conditioning, etc.

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Frequently asked questions: Bias in research

Why is bias in research a problem?

Bias in research affects the validity and reliability of your findings, leading to false conclusions and a misinterpretation of the truth. This can have serious implications in areas like medical research where, for example, a new form of treatment may be evaluated.

What is the difference between observer bias and actor-observer bias?

Observer bias occurs when the researcher’s assumptions, views, or preconceptions influence what they see and record in a study, while actor–observer bias refers to situations where respondents attribute internal factors (e.g., bad character) to justify other’s behaviour and external factors (difficult circumstances) to justify the same behaviour in themselves.

What is the difference between response and nonresponse bias?

Response bias is a general term used to describe a number of different conditions or factors that cue respondents to provide inaccurate or false answers during surveys or interviews. These factors range from the interviewer’s perceived social position or appearance to the the phrasing of questions in surveys.

Nonresponse bias occurs when the people who complete a survey are different from those who did not, in ways that are relevant to the research topic. Nonresponse can happen either because people are not willing or not able to participate.

What are demand characteristics?

In research, demand characteristics are cues that might indicate the aim of a study to participants. These cues can lead to participants changing their behaviors or responses based on what they think the research is about.

Demand characteristics are common problems in psychology experiments and other social science studies because they can bias your research findings.

Why do demand characteristics matter in research?

Demand characteristics are a type of extraneous variable that can affect the outcomes of the study. They can invalidate studies by providing an alternative explanation for the results.

These cues may nudge participants to consciously or unconsciously change their responses, and they pose a threat to both internal and external validity. You can’t be sure that your independent variable manipulation worked, or that your findings can be applied to other people or settings.

How do I prevent demand characteristics?

You can control demand characteristics by taking a few precautions in your research design and materials.

Use these measures:

  • Deception: Hide the purpose of the study from participants
  • Between-groups design: Give each participant only one independent variable treatment
  • Double-blind design: Conceal the assignment of groups from participants and yourself
  • Implicit measures: Use indirect or hidden measurements for your variables
Why is attrition bias a problem?

Some attrition is normal and to be expected in research. However, the type of attrition is important because systematic research bias can distort your findings. Attrition bias can lead to inaccurate results because it affects internal and/or external validity.

How do you prevent attrition?

To avoid attrition bias, applying some of these measures can help you reduce participant dropout (attrition) by making it easy and appealing for participants to stay.

  • Provide compensation (e.g., cash or gift cards) for attending every session
  • Minimise the number of follow-ups as much as possible
  • Make all follow-ups brief, flexible, and convenient for participants
  • Send participants routine reminders to schedule follow-ups
  • Recruit more participants than you need for your sample (oversample)
  • Maintain detailed contact information so you can get in touch with participants even if they move
How do you overcome attrition bias?

If you have a small amount of attrition bias, you can use a few statistical methods to try to make up for this research bias.

Multiple imputation involves using simulations to replace the missing data with likely values. Alternatively, you can use sample weighting to make up for the uneven balance of participants in your sample.

Why are placebos used in research?

Placebos are used in medical research for new medication or therapies, called clinical trials. In these trials some people are given a placebo, while others are given the new medication being tested.

The purpose is to determine how effective the new medication is: if it benefits people beyond a predefined threshold as compared to the placebo, it’s considered effective.

What is the difference between belief bias and confirmation bias?

Belief bias and confirmation bias are both types of cognitive bias that impact our judgment and decision-making.

Confirmation bias relates to how we perceive and judge evidence. We tend to seek out and prefer information that supports our preexisting beliefs, ignoring any information that contradicts those beliefs.

Belief bias describes the tendency to judge an argument based on how plausible the conclusion seems to us, rather than how much evidence is provided to support it during the course of the argument.

What is positivity bias?

Positivity bias is phenomenon that occurs when a person judges individual members of a group positively, even when they have negative impressions or judgments of the group as a whole. Positivity bias is closely related to optimism bias, or the expectation that things will work out well, even if rationality suggests that problems are inevitable in life.

Why is perception bias a problem?

Perception bias is a problem because it prevents us from seeing situations or people objectively. Rather, our expectations, beliefs, or emotions interfere with how we interpret reality. This, in turn, can cause us to misjudge ourselves or others. For example, our prejudices can interfere with whether we perceive people’s faces as friendly or unfriendly.