More than simply calculators, Mentats possess exceptional cognitive abilities of memory and perception that are the foundations for supra-logical hypothesizing.
Mentats are able to sift large volumes of data and devise concise analyses in a process that goes far beyond logical deduction:
Mentats cultivate "the naïve mind", the mind without preconception or prejudice, so as to extract essential patterns or logic from data and deliver useful conclusions with varying degrees of certainty.
So the Mentat is not a purely "left brain" type of intelligence with only a simplistic-autistic cognition, they are profoundly aware of nuance, subtlety and the kind of "sensitivity to initial conditions" which is studied in Chaos theory.
Additionally, they take in information through visual as well as other media and their calculations are delivered not as numerical probabilities but as flowing paths, subject to new variations through the influence of new factors.