The concept you are referring to is often associated with the observer effect or the measurement problem in quantum mechanics. According to the traditional interpretation of quantum mechanics, the act of measurement or observation can disturb the quantum system being observed, leading to a change in its state.
However, it's important to note that the notion of "observation" in quantum mechanics is not limited to conscious human observers. In quantum mechanics, an observation refers to any interaction or measurement that extracts information from a quantum system. This interaction can be between a quantum system and a measuring apparatus, regardless of whether it involves human consciousness.
Regarding your question about the impact of the first observation on subsequent observations, it depends on the specific situation and the nature of the system being observed. In some cases, the act of measurement can "collapse" the quantum state of the system into a specific eigenstate, and subsequent measurements will yield consistent results with respect to that collapsed state.
However, there are instances where subsequent observations can still exhibit quantum fluctuations and uncertainties, even after an initial observation. These fluctuations can arise from the intrinsic probabilistic nature of quantum mechanics and the uncertainty principle. In such cases, multiple observations of the same quantum system may not necessarily result in an "average" change but rather reveal the inherent probabilistic behavior of the system.
It's worth mentioning that there are different interpretations of quantum mechanics, such as the Copenhagen interpretation, the many-worlds interpretation, and others. These interpretations provide different perspectives on how to understand the implications of the observer effect and the behavior of quantum systems. The nature of quantum measurement and its relationship to subsequent observations continue to be topics of active research and philosophical debate within the field of quantum mechanics.