There are spells for measuring three mental traits, two of which clerics may use, all three of which may be used by wizards; Iker Egobar has not requested them today, and so cannot test them on Merrin, though, under the circumstances, he would not particularly expect them to work on her.
(It is better if Merrin does not particularly think that mind-reading spells might be effective on her.)
Speaking this language, the thought has occurred to him that the Taldane word 'Intelligence' is perhaps not well-translated as the Baseline intelligence.* 'Intelligence' is - quickness of wit, ability to visualize complicated things, good memory, thinking of many ideas. 'Wisdom' is clarity of perception, self-awareness, taking on others' perspectives, rejecting the bad ideas you think up. The third easily-measurable mental trait is 'Splendour', self-control, strength of will, force of personality, persuasiveness.
(*) Lit. 'thinkoomph'.