What is a major disadvantage of controlled observations?

Controlled observations involve a structured environment where variables can be manipulated and controlled to observe specific behaviors. A major disadvantage of this method is that they can produce demand characteristics, which occurs when participants alter their behavior because they are aware that they are being observed or have guesses about the study's purpose. This awareness can lead to results that do not accurately reflect natural behaviors, as participants might act in ways they believe are expected or desired by the researchers, thus compromising the validity of the findings.

The structured nature of controlled observations often detracts from the authenticity of the participants' responses, as their behavior may not be genuine. This can skew the data and affect the conclusions that researchers draw from their observations.

In contrast, the other options, while they may represent potential concerns in research design, do not pertain specifically to the inherent issues of controlled observations as demand characteristics do. For instance, reliability can be high in controlled observations due to their structured nature, and the need for a natural environment is not a requirement for this observation method, while replication depends more on the study design and findings rather than being a specific drawback of controlled observations.