Evaluate the validity of a lab experiment.

One reason a lab experiment could be considered high in internal validity is the increased level of controls over the extraneous variables. This lowers the risk of findings being due to conditions which weren't planned for in the study e.g. room temperature, noise levels etc. This increases the internal validity as findings from lab experiments are more likely to show an accurate cause and effect relationship between the independent and dependent variables.
In contrast, lab experiments may actually lower validity. This is because the findings from the experiment may not accurately reflect those present in the real world, and may be novel, and only applicable to the artificial lab environment. This lowers validity as we cannot extend findings from the study to real life, and develop effective practical applications from the results.