Informed consent can introduce bias by changing who agrees to participate or by revealing information that changes participants’ behaviour. The right to withdraw can create bias when withdrawal is systematic, leaving a final sample that differs from the original sample. Both remain essential ethical considerations.
| Ethical consideration | How bias arises | Likely effect |
|---|---|---|
| Informed consent affects participation | People who volunteer may be more interested, confident, or comfortable with the topic than those who refuse. This produces volunteer bias or self-selection bias. | The sample may not represent the target population, reducing population validity and generalizability. |
| Informed consent reveals purpose | Detailed information may create demand characteristics. Participants may guess the hypothesis and alter their behaviour. | Behaviour becomes less natural, reducing internal validity. |
| Right to withdraw | If particular participants are more likely to leave, attrition bias occurs. Highly anxious participants, for example, may leave a stressful procedure more often. | The remaining sample becomes systematically unrepresentative, potentially distorting findings. |
This problem is important in research on social responsibility, including bystanderism. In Darley and Latané’s 1968 seizure experiment, participants believed another person might be having a seizure. If fully informed that the study examined helping during a staged emergency, they might have helped because they recognized the expected response, rather than behaving naturally.
However, withholding the true aim involves deception. Researchers may use general consent, minimize harm, preserve withdrawal rights, and provide a full debriefing. Ethical protection takes priority over perfectly unbiased data.
A common misconception is that withdrawal rights automatically make research biased. Bias occurs only when withdrawal is systematic rather than random; random withdrawal may reduce sample size without systematically changing its composition.
Exam technique: Identify the ethical principle, explain the bias, and link it to validity or generalizability. Apply the point to a relevant study instead of listing ethical guidelines.