In an Experiment, the Researcher Was Unintentionally Talkative to One

Multiple Choice

In an experiment, the researcher was unintentionally talkative to one of the participant groups. What best describes the threat to internal validity and why is it a threat?

A) Randomness, since being talkative can make this particular group more relaxed and better able to perform.
B) Participant-maturation interaction, since being friendly to one group can introduce a confound.
C) History, since this unintended interaction was not part of the independent variable, a confound was introduced.
D) Testing, since the other group might feel cheated for being treated more formally by the researcher, and this introduces counterbalancing.