Which phenomenon refers to the effects on behavior caused by the administration of an inert substance?

The placebo effect is the phenomenon where a person's behavior or symptoms improve after receiving an inert substance, often referred to as a "placebo," which has no therapeutic effect. This effect highlights the powerful role that expectations and beliefs play in the healing process. When individuals believe they are receiving treatment, they may experience actual changes in their condition, including reductions in pain, anxiety, or other symptoms, purely based on their perception of the treatment's potential effects.

In clinical trials, the placebo effect is crucial for determining the efficacy of new medications or interventions. By comparing the outcomes of those receiving the active treatment against those receiving a placebo, researchers can better understand the true effects of the treatment itself, disentangling the psychological impact of treatment expectations from the physiological effects of the treatment.

The other options pertain to biases or effects not directly related to the administration of an inert substance. For example, confirmation bias refers to the tendency to favor information that confirms existing beliefs, while experimental bias relates to systematic errors that can affect study outcomes. Control effect is not a recognized psychological or medical term referring to this specific phenomenon.