In addition to showing a lower correlation (r linear = 0.82), raw scores also clearly posses a nonlinear component, and in fact the quadratic trend is highly significant (t quad = 13.10, p < .001).
often, such evaluations are based on the use of simple sum-scores (i.e., the number of correct answers) and derivatives thereof (e.g., percentages), or on ad-hoc ways to rank or order system responses according to their correctness.