I think I’d use the word:

inducement-

a positive motivational influence

act of bringing about a desired result

OR

incentive-

Serving to induce or motivat

OR

stimulus-

Something causing or regarded as causing a response.

catalyst

noun

1. (chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected [ant: anticatalyst]

2. something that causes an important event to happen; “the invasion acted as a catalyst to unite the country”

RE:
whats the definition of catalyst?
what do you like about coffee?

– it's a good social catalyst meaning that it brings people together.

does that make sence??

or is there another way of sayin this?

Something which speeds up a chemical reaction