What doctor spends the least amount of time in school?

Anyone with a doctorate has completed at least 8 years in university/college, that is a 4 year undergraduate degree and a 4 year postgraduate degree. This includes medical doctors, chiropractors, dentists, optometrists, scientists, veterinarians, etc.

However, some doctors spend additional time in school before they work. The best example is medical doctors, who all must complete at least three additional years in school (actually called a residency) before they can practice medicine. Further, within medicine, different specialties require different lengths of residencies, with family doctors requiring the least, and neurosurgeons requiring the most additional training.