Dr. Park identified 20 restrictive eaters (people who constantly monitor and limit their caloric intake) and 20 matched control participants. She then manipulated and randomly assigned whether each participants had or had not just consumed a high calorie milkshake prior to taking part in a “taste test” of chocolate chip cookies. She found that whereas the control participants ate fewer cookies than usual after having just consumed the shake, the restrictive eaters actually ate more. Dr. Park’s study is: