Dr spelke thinks language is highly involved with spatial ability she enlists college to do verbal task while they navigate around a room while another group of students does a nonverbal tapping task while also doing the same navigation task what is the purpose of the tapping group

The answer to this question is: They are the control group
Control group is a part of experiment's subject that do not receive treatments by the researchers, unlike any other subjects.
The main purpose of this is so the researchers could make the data collected by the control group as a benchmark to determine whether the treatment affect the outcome experiments or not..

The  ancient egyptians  who  built the pyramids  may have been  able  to move massive stone blocks across the desert by wetting the sand in front of a contraption  built  to pull the heavy objects