A term from improv comedy. Shorthand for a heuristic for a "move" in a collective improvisation in which one accepts the new material in another's preceding move and elaborates on it. It would seem to be relevant to WikiZenhood.
The AntiPattern is called "denial". A classic example from Del Close (inventor of the Harold, a long-form group improvisation that becomes a three-act play) occurred in an improvised scene between himself and Joan Rivers in an early Second City show:
The purpose of YesAnd is to collaboratively create a consistent reality, and to do so efficiently--that is, no "waste." (In the scene above, Joan, through her denial, wastes Del's attempt to add information to the reality--the fact that the couple has kids.)
Denial isn't always an AntiPattern, it's just that it should be used judiciously. It actually pops up frequently in improv, when, all by itself, it gets a laugh because of a silly incongruity it creates. But doing it randomly is just being uncooperative, so of course things fall apart.
Whether done randomly or for a laugh, however, the burden of the next move to keep things going falls on the performer who did the denial, since it usually prevents the other(s) from having a smooth continuation. So you could say that it's an AntiPattern to do just the denial, and wait expectantly, leaving the partner gasping for air. The speechless discomfiture is sometimes funny (although not very friendly), but it has to quickly move on in some way.
See:
See also: ExpandToContractContributors: ApoorvaMuralidhara, AnonymousDonor(s)
Also a DungeonsAndDragons DM guideline. Suppose your party is hunting for the evil Lich who keeps sending minions after them. A Lich is an undead Wizard who tried one too many immortality spells. The party might think to find the nearest Wizards Guild, to look for historical records of the wizard who might have Lich'd-out.
The Dungeon Master should not just say "you can't find a nearby Wizards guild", if the DM did not prep for this line of inquiry. The DM should instead roll d6, where 6 == the guild is in a fortress beyond some savage mountain frontier, and 1 == the humble peasants' inn where the party is staying is secretly a front for the guild, literally under the party's feet. The DM then fleshes out this scenario, on the spot (using random dungeon and NPC generation rules), and these could lead to permanent fixtures of the DM's campaign.
I don't know about anywhere else but certainly in the UK "Yes, And..." is a sarcastic/also humorous denial of the importance of a persons statement. But here it's more of a "and this, and this, and this..." sort of statement
You can't interpret these things out of context. It is quite possible to say "Yes, and..." in British English without being sarcastic. Here, the question is merely what the page creator was trying to say, that's all. YesAnd is an abbreviation of a large concept, not something you can figure out purely from those two words.
Similarly the single word "so" all by itself can take on many meanings depending on tone of voice. Similarly with many things.
If you follow the link he provided, it is even more clear that this is not about sarcasm.
so it's not about tone but more about semantics, "yes" being the controlling aspect (I acknkowledge what you are saying) and the "And" putting the speaker back in control of the improtance i.e. I'll add to that by saying bla bla bla. I met someone who conducted every conversation that way, but with a 'better that you'' clause to each addaitve eg. A: I met Bruce Springrstein once. B: I met him to and I got his autograph A: I did to, we sat and had drinks once. B: yes and I played fencing with him that day. A: really, I did that too. B: yes and I have his jacket. A: we swaped phone numbers b: and he wrote his email address on the back... and so on... " he was quite an annoying person.
YesAnd can be a healthy and practical means of offering palatable disagreement to managers. Contrast with NoBut?, which gives you a reputation for being negative and obstructionist--NotaTeamPlayer.
From the Extreme Programming yahoogroup:
One trick I stole from improvisational theater training is known there as "Yes And".
When practicing "Yes And", the game is to never say no, to never say anything that sounds negative at all. But this doesn't mean you should be mindlessly compliant. (In improv the fun comes in how far you can twist things while still saying yes. In real life, though, stick to your more serious goals.) You have two ways you can steer the conversation: one is in picking which portion you say yes too, and the other is what comes after "and".
For example, you could say, "Yes, an initiative to improve quality would be great! And experts say the three top techniques for that are unit testing, pair programming, and acceptance testing! So let's get started today!"
Now you'll note that gushes enthusiasm. There's nothing even slightly negative about it. But note also that you haven't agreed to their implied diagnosis of the problem or accepted their mandate. However, if the things you agree to are important principles or goals that you both share, they will rarely notice and never care that the plan is, eventually, completely different.
In real life, of course, you rarely can switch things around with three quick sentences. But patient application of "Yes And" can often get you much farther than rational disagreement, even if the logical content is the same.