If I try to project a "thought", or an idea, it will be difficult to determine exactly when an answer is a hit, and when it is a miss (it is easier when the target is a number). I tried to use words recently in another test (on another forum), but the results were not good, words may be less "neutral" than numbers, people might answer the word they "like best", or they feel is the most "appropriate". Also, numbers may seem more "scientific", which may give an psychological advantage in a scientific experiment. Also, with numbers, I can say "numerical correctness".