What do you call the fallacy of "seeing the effect and assuming the cause"?

I often come across cases that I have labeled as "seeing the effect and assuming the cause". Is there a specific Dr. Bo's fallacy that covers this.

Here are some examples - 

1. Jack is all alone in a room. John enters the room to find that Jack's pants are wet. John concludes that Jack peed his pants when in reality Jack's pants are wet because Jack was drinking water from a glass and accidentally split some water onto his pants. Here, John sees the "effect" (Jack has wet pants) and assumes the "cause" (Jack peed his pants) when the "real cause" is something else (Jack mistakenly poured water onto his pants).

2. Samantha looks outside her window to see that the sidewalk is wet. She assumes that it rained. However, the sidewalk is wet because the street cleaner watered it with a hose.

3. People assuming that aliens exist because the US government has confirmed certain UFO sightings when in fact these UFO sightings could have been caused by something else.

I'm not sure if the above 3 examples would constitute different fallacies. If so please label each of them separately.

Check out post hoc and the more casual jumping to conclusions . All the examples you mention would fall under these, if in argument form. Otherwise, at least for the first two, these might just be reasonable initial assumptions, and if the people in the examples seek clarity after making the assumption, no problem with reasoning.

For the 3rd example we can say it also is an example of the least plausible hypothesis fallacy. This is in a different class because the default assumption is not the reasonable conclusion.

Ah, yes, the old "Pee-Pants Fallacy." An underdiscussed topic in the annals of higher thinking, I assure you.

In actuality, each of these instances does indeed possess a common thread: the logical fallacy known as "post hoc ergo propter hoc," or "after this, therefore because of this." This fallacy occurs when an observer jumps to an immediate conclusion about a cause, simply because it appears after an effect. In layman's terms, if event B happened after event A, then everyone assumes event A caused event B. Burp after eating a sandwich? Must have been the sandwich. Fall as soon as you step on a banana peel? Must have been the banana peel. Cat gives you a sideways look just before the earthquake? Cat must have super seismic powers!

In your example, Jack's wet pants, the wet sidewalk, and UFO sightings are each an effect, and the cause is presumed based on a preceding event or situation. However, the reality is more complicated. Poor Jack might be a clumsy water-drinking champ, the sidewalk's wetness could be thanks to civic duty, and UFO sightings are...well, we'll leave that one to the Mulder and Scully in us all.

This particular faulty reasoning is often accompanied by a healthy dose of confirmation bias. That's when you favor information that confirms your own pre-existing beliefs. The rain-loving Samantha assumes a soggy sidewalk is due to precipitation, not pedestrian hygiene. John goes for the easy narrative that Jack's "accident" has nothing to do with his poor hand-eye coordination around hydration vessels. And let's not get started on the extraterrestrial enthusiasts.

Remember, just because something happens after another thing, does not mean there's a cause and effect relationship. That's like assuming the sun rises in the morning because you turn off your bedside lamp. Although, I must confess, it's a delightful boost to one's ego, being a morning luminary and all.

Hi, Prithvi!

The first two scenarios do not present arguments, so no fallacy can be identified in them. You essentially write that Jack and Samantha each saw something and drew a conclusion. We don’t know how they drew their conclusions. 

To preempt a reply that says I am supposed to interpret Jack’s and Samantha’s observations as being a premise, I will point out that they still would not commit the post hoc ergo propter hoc fallacy even if their arguments were along the lines of: 

1. John’s pants are wet (or, the sidewalk is wet.)
2. Therefore, John peed his pants (or, it rained.)

An argument commits the post hoc fallacy when it draws a conclusion claiming that a causal relation holds between events from premises asserting only a temporal relation between events. However, Jack and Samantha do not assert as a premise a temporal relation between peeing and wetting pants, or between raining and having a wet side walk. Also, Jack and Samantha do not conclude that John peeing caused the wet pants or raining falling caused the wet sidewalk. Rather, they conclude that John peed his pants and that it rained. The idea that peeing causes wet pants and rain causes wet side walks would seem to be an implicit premise, not the conclusion.

The third example is the only one clearly an actual argument. It commits a non sequitur, if it is a deductive argument. A UFO is not necessarily occupied by aliens. If the argument is inductive, refer to Dr. Bennett’s Answer regarding the least plausible hypothesis fallacy. 

Now let me answer the title question. As for what the fallacy is of seeing the effect and assuming the cause, there is no fallacy for such an act. That is because a logical fallacy occurs in the course of an argument or inference. But a cause that is argued for or inferred to is not assumed. If you meant to ask about what the fallacy is of seeing the effect and drawing a conclusion as to the cause, well that depends on how the conclusion was drawn. By itself, the act of drawing a conclusion from seeing an effect is not fallacious. 

Thank you, Prithvi

From, Kaiden

You describe exactly the affirming the consequent  fallacy.

The negated form of that, is the denying the antecedent which is also fallacious.

In both cases the fallacy lies in ignoring that there may be multiple ways that a result may have been reached.