Everybody has been on that slow tip from time to time. Some people are stuck on that slow tip. Others are only temporarily intoxicated, distracted, or just not feelin it.
You may notice the person isn't all there or doesn't seem aware of people growing impatient around him. Whether he is painstakingly counting and recounting his change at McDonald's before giving up and handing over another dollar bill; taking forever to pack a bowl while sober bitches around him start walking away; or can't stop talking about a movie that everyone else saw 2 years ago; the fool ain't dumb, he just be on that slow tip.