Which aspect of the study gave it high ecological validity?

High ecological validity refers to the extent to which the findings of a study can be generalized to real-world settings. In this case, the realistic setup simulating an actual prison is what gives the study its high ecological validity. Such a setup immerses participants in an environment that closely resembles the conditions they would encounter in a real prison, enhancing the authenticity of their experience and interactions. This authenticity helps researchers draw better conclusions about behavior in naturalistic settings, making the study's findings more applicable to real-life scenarios involving prison environments.

The other aspects of the study do not contribute similarly to ecological validity. For instance, random allocation of participants primarily relates to the internal validity of the study, ensuring that any observed effects can be attributed to the experimental manipulation rather than pre-existing differences among participants. Similarly, the extensive use of reward systems may manipulate behavior but does not directly reflect the complexities of real-world prison environments. Lastly, monitoring participant behavior is crucial for data collection but does not impact the ecological context in which that behavior occurs.