my thoughts would be the sphincters have a cell memory, like all cells in the human body , every tissue and organ has a cell memory and acts like it does in relation to life experiences we have had.
why would the sphincters be closed shut all the time when there is an urge to go in public?
because the public is a threat to the relaxing mechanism of relaxing to go to the loo, there fore resistance is sought to fight or defend the threat.
they are valves that open and shut voluntarily with our conscious control aswell.
if our conscious control says we are safe and happy we will evacuate accordingly well and have a good poo.
if our conscious control says we feel unsafe because public toilets are not private enough, visitors at our home threaten our privacy, any public or social face will THREATEN the RELAXING mechanism for sphincter to RELAX, once threatened it will resist the experience no matter what.
it is the terrifying fear of pooing in public and how can we possibly relax through this? how do we desensitize our terror into self achievement and pleasure?