Final answer:
The principal weakness of laboratory-based studies is often the artificial nature of the lab setting, which can limit the generalizability of the findings, in addition to the high costs associated with such experiments.
Step-by-step explanation:
The major weakness of a laboratory-based study is not that experimental variables cannot be easily controlled or that it is difficult to replicate the findings, nor that the results cannot be applied to human beings; on the contrary, experiments provide a high degree of control, which allows for replication and application to humans when ethically permissible. Instead, the major weakness is often related to the artificial setting of the laboratory, which might not accurately reflect real-world conditions.
This can limit the generalizability of the findings to real-world scenarios. Moreover, the costs associated with maintaining such controlled environments can often be quite high. However, it is important to recognize that this question seems similar to one discussing the limitations of case studies where the inability to generalize findings to the larger population is a noted limitation. It's crucial to distinguish that the context and nature of the study greatly influence its weaknesses.