There's a fairly common scenario where negative signals are given in a "positive" form.

Example: You've spent the day with friends and they are dropping you off at your house. One party, usually the husband, not knowing the code says "com'on in for dinner (or a beer)". The other, usually the wife, knowing that the house is a mess and that she was preparing leftovers for dinner says, "Oh yes, won't you come in". The husband of the couple dropping you off says, "sure", however, the wife of the couple dropping you off, also knowing the code, immediately says "oh thank you very much, but we have to get back". That usually ends it. I've always known this process as "knowing the social code", but there may be a better, more concise, term.