This trial is testing a new device that may help to understand and treat chronic constipation. The device, called Fecobionics, is a simulated stool that records pressure, cross-sectional area, orientation, bending, and shape of the rectum and anal canal simultaneously. The goal is to study the defecation dynamics in normal control subjects and compare them to patients with chronic constipation to see if abnormalities of rectal contraction contribute to the condition.