Answer: (C) The placebo effect
Explanation:
The placebo effect is one of the type of treatment that is specifically designed for control all the therapeutic values and this effect is basically works on the various types of symptoms that is generated by our brain.
It includes the various types of procedures, inert injections and the tablets. The researcher utilized various types of placebo effect controlling system so that they can easily assess our memory.
According to the given question, the given situation is due to the placebo effect as they can easily determine the quantity of caffeine in the memory.
Therefore, Option (C) is correct.
If you mean which species, it would be the Homo sapiens.
