Answer : Hopi.
Explanation : The Hopi tribe who are a Native American tribe, are the ones who primarily lived on the Hopi Reservation in northeastern Arizona.
These were the group of people who believed that humans emerged from a hole in the earth.
The variable is the group that was given caffine, because thats what the doctors manipulated. They possibly altered the natural memory of the participants by giving them caffine. A more specific variable could be how much caffine each participant is given and what time are they given it.
Yes yes for sure no problem my boy lemme go get him
