Final answer:
In the described study, a control group is being used to evaluate the effects of a new attention deficit disorder medication and to control for the placebo effect and experimenter bias.
Step-by-step explanation:
The scenario described involves a research study to evaluate the effects of a new attention deficit disorder medication. Given the details provided, the element being used in this study is a control group. A control group is essential in experimental design to compare the treatment effects of the new medication against a baseline, where the control group typically receives a placebo. This setup allows the researchers to separate the effects of the treatment from any other factors, like participant expectations which can lead to a placebo effect, whereby individuals experience a perceived or actual improvement in their condition simply because they believe they are receiving a treatment.
The placebo effect is minimized by the use of blinding, where participants are unaware whether they're receiving the real medication or a placebo, and double-blind studies further reduce this effect by keeping both participants and researchers blind to who receives the active treatment.