Jack Nicholson's character Edward Cole in the movie The Bucket List said ...and never trust a fart, and a search for Al Roker leakage White House will clear up any doubts what that's all about.

How is the adult human body usually able to sense the difference between solid, liquid, and gas and enable the brain to consciously decide on the proper course of action? (e.g stay put, walk, or run!)

Per @theforestecologist's request I'll restate the question using my best "science words": How are adult humans able to determine when pressure in the rectum is the result of solid waste, liquid waste, or flatulence?

A search for answers has turned up the following:

Source: https://www.sharecare.com/health/digestive-health/how-can-i-have-normal-bowel-movements

In a rapid "sampling reflex," these nerves inform the brain about whether the rectal contents are intestinal gas or liquid or solid stoo...

However I can't view this link further.

Searching further for "sampling reflex" I've found this

  1. Sensing of the arrival of stool in the rectum with activation of the recto-anal inhibitory and sampling reflexes which allow stool to enter the anal canal and to be distinguished from flatus.

This provides an opportunity for sensation to take place, but does not describe how stool is distinguished from flatus, and doesn't even mention liquid.

At this point I'm way out of my depth.

  • 1
    $\begingroup$ I actually think you've asked a valid scientific question here, but you've wrapped it in so much non-serious, non-scientific baggage that others are almost certainly to judge this question negatively. I don't think it should be closed (fyi it's not "opinion-based" as one close voter has suggested), but if you do not edit the question you'll have a tough time keeping it positive or getting an answer. Please update accordingly. $\endgroup$ Feb 11, 2019 at 5:15
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    $\begingroup$ @theforestecologist thank you for recognizing the validity of the question, but I think the wording is quite positive! Nonetheless I've added a third sentence. fyi informal words like "fart" have been used in this SE site on many occasions without issue. Biologists are generally comfortable with discussing the human body and it's functions without hiding them unnecessarily behind clinical terminology, and I think in this case a clinical view is not necessary. $\endgroup$
    – uhoh
    Feb 11, 2019 at 5:38
  • $\begingroup$ you've misunderstood me a bit. it's not the topic or even your choice of using the word "fart" -- these are ok in my opinion. Your entire 1st paragraph is unnecessary and distracting and sets the tone that your question is not serious but rather, it comes across as juvenile. I would delete the first paragraph & perhaps provide more biologically-focused background. We do ask that all question askers provide evidence that they researched their own question, so I recommend that you do some research on your own and then update the question by adding a bit more scientifically-relevant info. $\endgroup$ Feb 11, 2019 at 5:45
  • $\begingroup$ @theforestecologist okay that's a more concrete suggestion, thanks. While I won't remove the levity or existing "research", I've "given it a go" so to speak and added some additional research. $\endgroup$
    – uhoh
    Feb 11, 2019 at 6:06
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    $\begingroup$ Your sphincter is smarter and more athletic than you realize! :-) $\endgroup$ Feb 12, 2019 at 9:27


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