We can explore being thirsty but refusing to drink by first identifying the conditions of a response (in this case, the body's need of hydration) against the features that something must possess in order to do so (the mind's willingness to drink). With respect to humor, we make the reverse comparison - our ability to isolate the psychological process that results in laughter, but inability to isolate the origin of humor (thirst).
When we attempt to define humor, we often evaluate the characteristics of the response (i.e., a laugh or smile) more than we evaluate the origin of humor, especially in light of the multitude of experiences people find humorous. We classify those multitudes of humorous experiences into categories based on the responses they evoke within us. We then propose new theories and definitions of humor based on those responses. Finally, we biologically question whether these responses are features specific to humans.
In the parable, it's almost ridiculously easy to pinpoint his problem with drinking when he's thirsty as a psychological one. Cognitively speaking, he knows he needs to drink something, that he's severely dehydrated, and that without water he could die. In spite of his thirst, other forces impede his ability to enjoy a refreshing, much needed drink so he psychologically refuses to do so. He concludes that he cannot possibly drink the entire river, which he has placed as a stipulation upon his becoming hydrated, and thus refuses to drink what little he needs to live.
The parallel with humor is that we often think something is more humorous if it produces a laugh. However, depending on someone's psychological disposition and cognitive stipulations, a joke may simply evoke a smile. Is the joke less funny for this person? Is someone who laughs easily more dispositioned for humor?
Maybe someone who simply smiles but cannot laugh is the same as someone who arrives thirsty to a river but for whatever reason cannot drink. Meaning, maybe the origin of humor is both cognitive and psychological. Cognitively speaking, humor may be rooted in our acknowledgement of incongruity, superiority or inferiority, but psychologically, it's rooted in acceptance and permission. In this respect, we must psychologically give ourselves permission to experience the feelings evoked by a cognitive judgment.
If we cognitively "miss" a fact about what we psychologically want or don't want to experience, we can find ourselves, irrespective of our disposition, in a pretty humorous situation - at least for others!
Like the Chicken who opts for hypnosis as a cure for his fear of losing control.
Spray-painting "Vandalism Sucks" on a wall.
Pointing but failing to click.
Committing to a Fear of Commitment Support Group.
When will we learn that humor, like life, is simply giving ourselves permission to laugh?