‘Mental models’ used by automated scoring for the simulation divisions of the computerized Architect Registration Examination are contrasted with those used by experienced human graders. Candidate solutions (N = 3613) received both automated and human holistic scores. Quantitative analyses suggest high correspondence between automated and human scores; thereby suggesting similar mental models are implemented. Solutions with discrepancies between automated and human scores were selected for qualitative analysis. The human graders were reconvened to review the human scores and to investigate the source of score discrepancies in light of rationales provided by the automated scoring process. After review, slightly more than half of the score discrepancies were reduced or eliminated. Six sources of discrepancy between original human scores and automated scores were identified: subjective criteria; objective criteria; tolerances/ weighting; details; examinee task interpretation; and unjustified. The tendency of the human graders to be compelled by automated score rationales varied by the nature of original score discrepancy. We determine that, while the automated scores are based on a mental model consistent with that of expert graders, there remain some important differences, both intentional and incidental, which distinguish between human and automated scoring. We conclude that automated scoring has the potential to enhance the validity evidence of scores in addition to improving efficiency.