I think that. When I drink socially, I'm engaging with other people and things like slurring speech become readily apparent. I can tell when I'm stumbling over words and having trouble saying what I mean. It's very obvious. When I drink alone, I'm not talking to anyone. The voice in my head never gets noticeable inebriated. I'm typically not moving around as much so can't rely on my sense of balance to judge intoxication as reliably either. And with social drinking, it's pretty easy to compare the rate at which I'm knocking back drinks versus everyone else. You tend to order in waves with others which slows folks like me down quite a bit.