Final answer:
Maturation is the risk to a study that exists regardless of participant communication, as it encompasses the natural changes participants experience over time that can affect study outcomes.
Step-by-step explanation:
The risk to a study that exists whether or not participants in different groups are able to communicate with each other is maturation. Maturation refers to the biological and psychological processes that occur within participants naturally over time, which can affect study outcomes independently from the experimental interventions. It's a form of internal validity threat that can influence the results of a study due to participants aging or growing during the duration of the study.