What constituant in coffee has a laxative effect? My question is as simple as it sounds. I want to know which constituent in coffee makes me poop, chemical or physical (particle).

I'm sure everyone has experienced it. You drink a (couple) cup(s) of coffee and a few minutes later you'll find yourself rushing to the toilet.
I personally don't drink a lot of coffee. I drink one cup a day (only from We. to Fr.) and occasionally a cup on Weekends.

What ingredient causes this laxative effect?


Is it the caffeine?


If so, why doesn't energy drinks have a similar effect?

Is it something out of the coffee bean itself?
Do only special types of coffee (bean) have this laxative effect?


I tried googling a bit, but haven't found a meaningful answer. Seems like scientists can't agree which ingredient causes it or whether it's even scientifically proven that coffee has a laxative effect.
Disclaimer: I am not a doctor, nor do I play one on TV...

I would guess that it is a combination of a few factors.


Coffee contains caffeine which is a stimulant and most stimulants have some degree of laxative effect. 


If nothing else stimulants will raise your metabolism, so even if it isn't immediate you'll be heading to the bathroom sooner than you would without them. 
It also looks like caffeine causes stimulation of the bowels specifically. 


  coffee can also cause looser stools because increased peristalsis
  leaves less time for the colon to perform one of its key
  functions–reabsorbing water from fecal matter to produce well-formed
  stools. Be aware, however, that other common accompaniments to coffee
  can be culprits in this matter. Dairy products, excess sugar, even
  “sugarless” sweeteners like sorbitol (a well-known substance used as a
  laxative) can cause diarrhea. - Source


Coffee is mostly water  


Just drinking a couple full glasses of water on an empty stomach can lead to a softer stool.

The psychological effect  


I don't know if there have been any real studies on this, but I strongly suspect that there is some Classical Conditioning going on. Much like Pavlov's dogs who were conditioned to salivate at the sound of a bell, if your usual morning routine is to have a cup of coffee and then head to the restroom, over time you end up conditioning your self to do this regardless of whether or not the coffee is really "making you poop".