Dr. Jack Daniels wanted to know whether alcohol intoxication alters drivers' reaction times. Reaction times were measured in a driving simulator machine. The same participants took part in both the control and alcohol conditions. On the evening of the study's first day, participants were given enough alcohol to keep blood alcohol content well above the legal limit for many hours; then they were tested in the simulator. This condition concluded about 1 AM. The control condition took place VERY EARLY THE NEXT MORNING, as soon as blood alcohol levels returned to normal. The information in CAPITALS raises questions about:_________.