| Intellectual ability | Sample 1 1880-1890 N = 119 | Sample 2 1985-1987 |
| Number of patients with above average intelligence | 22 (19.6%) | 32 (24.2%) |
| Number of patients with average intelligence | 62 (55.4%) | 74 (56.1%) |
| Number of patients with lower than average intelligence | 28 (25.0%) | 26 (19.7%) |
| Total | 112 (7 were not assessed) | 132 |