In his work on the two-point threshold, weber found that the most sensitive area (smallest threshold) was the and the least sensitive area (largest threshold) was the

tongue; middle of the back

Explanation:

In physiology, the two-point threshold means that there must exist a threshold distance, above which any given subject can differentiate between two different sensations. In physics, the two-point threshold is the smallest distance that exists between two points where the person can distinguish those two points as distinct and not one. This two-point threshold work by Weber found that the most sensitive area where the threshold distance was the smallest was the tongue and the least sensitive area where the distance was largest was the middle of the back.

I’m not really sure