Like any complex reaction there are probably a slew of chemicals and variables involved in the crush effect however it has been repeatedly demonstrated that A314 and A1 are the best at inducing this effect. I have a couple ideas why.
For A314 there are SOOOOO many chemicals in it we don’t know however we DO know that combined those chemicals tend to raise the person’s value. Fallout is essentially when a target develops one-itis over the user and begins bending over backwards. I’m sure there are lots of men (and perhaps women) who remembered that person way back when who they fell head over heels for and ended up catching one-itis over. You basically put a lot of value into that person which causes the sometimes beta or submissive behavior. If this sounds confusing this thread –>The "A314 Stalker Effect": A314/MX102 and female obsession will explain my point more clearly.
A1 is a little more straight forward because it’s a single molecule with loads of research behind it. Now scientifically it’s been proven that A1 tends to increase a person’s sensitivity to emotional stimuli. Now add in the fact that A1 probably the most reliable female relaxer and you can kinda see how it might induce that crushing feeling. Essentially, A1 primes targets and makes it easier for you to make a memorable impression and also might explain why A1 mixes well with some other mones in reasonable quantities. THIS, IMO, is also why so many A1 users report a “lingering” effect to A1 where the woman exposed will still treat them well even if they go mone-less. Unfortunately, this might also be why some men report a longing for an ex or experience increased affection towards a particular woman bordering on one-itis.
Another molecule that is reported to cause a crushing effect is P83. Now here’s the thing about P83: it’s a putative and until Androtics tells us the real name all effects are speculative however P83 benefits from a large amount of (anecdotal) evidence and testing most of which identifies it as a disinhibitor and as an emotion intensifier. Now if you read around, you’ll see some users (me included) who say P83 plays well with A1 and helps with the crush/falling in love effect. Well remember that A1 increases sensitivity to emotional stimuli and add in P83’s ability to intensify emotions while simultaneously making that person more willing to act on those emotions you can probably see why P83 and A1 make such a good team.
Again, as Mobo and others have alluded to, there is no one thing that does it, however I believe A314, A1, and P83 achieve e crush effect in the ways I just described.