How might participant expectations influence experimental outcomes?

Participant expectations can influence experimental outcomes by causing demand characteristics or placebo effects.

Demand characteristics refer to the cues that participants pick up from the experiment which allow them to guess the researcher's aims and thus change their behaviour accordingly. This can significantly influence the results of an experiment. For instance, if participants believe the experiment is testing for intelligence, they may try to perform better to meet these perceived expectations, thereby skewing the results. This is particularly problematic in psychological research where the behaviour being measured is often influenced by social and cultural norms and expectations.

The placebo effect is another way participant expectations can influence experimental outcomes. This occurs when a participant's belief in the effectiveness of a treatment causes them to experience a change, even though the treatment itself is inert. For example, in drug trials, participants who receive a sugar pill (a placebo) often report improvements in their condition simply because they believe they are receiving a real drug. This can make it difficult to determine the true effectiveness of the treatment being tested.

Moreover, participant expectations can also lead to self-fulfilling prophecies. This is when participants alter their behaviour to match their expectations, thereby making their expectations come true. For example, if a participant expects to do poorly on a task, they may not try as hard, leading to poor performance.

To mitigate these effects, researchers often use double-blind procedures, where neither the participant nor the experimenter knows who is in the control or experimental group. This helps to control for both experimenter and participant expectations. However, it's important to note that it's not always possible to control for these effects completely, and they represent a significant challenge in experimental research.

In conclusion, participant expectations can significantly influence experimental outcomes through demand characteristics, placebo effects, and self-fulfilling prophecies. Researchers must be aware of these potential influences and take steps to minimise their impact to ensure the validity of their results.