I was listening to an actual play of a group playing a game and when a roll provided an advantage the GM asked who rolled what they wanted their advantage to be. Is this normal? I thought the advantage was to be determined by the GM.

Technically the GM has final say, but it is encouraged that all players chime in on proposed ideas for the interpretation of dice rolls.

It varies, but typically the person who rolled the dice determines what the Advantage and Triumphs do, while the other side determines what the Threat and Despairs do.

So if a player rolls, they determine the good stuff and the GM determines the bad stuff, where as if the GM rolls she determines the good stuff and the players determine the bad.

Of course, since this game is cooperative, some collaboration on what everyone thinks would be coolest is always a good idea!

So if someone succeeds with threat, the GM decides what his downside is correct?

When the player rolls Advantage or Triumph, I give them first crack at the narrative options. Likewise if an NPC rolls Threat or Despair, I also give the players first crack. That said, sometimes they want more than is reasonable so adjustments must be made.

So if someone succeeds with threat, the GM decides what his downside is correct?

Correct.

Thanks everyone for clearing that up. I am loving this whole narrative dice over d20 immensely.

The rules on Advantage spending can be found in Chapter 1 of your core rulebook. Players by default choose how to spend their own Advantage/Triumph, and GMs by default choose how to spend any Threat and Despair.

However, this is a collaborative game, and the cooperative spirit should be in place and take precedence over these rules.

So if someone succeeds with threat, the GM decides what his downside is correct?

Typically, though if the player has a good idea and is willing to share it with the GM...

I ask the players all the time what they want to do with their advantage or threat. They often have better ideas then me.

As a player, I'm probably far more dangerous to my party than my GM with regards to threats/despairs.

Player: OK GM, I rolled a success and 3 threat when making the mechanics check to do the manual override to open the turbo lift door in the unpowered and abandoned facility.

GM: Good, well, the success means you got the door open, and three threat...You're all a bit annoyed by how long it took, setback for everyones next check

Player (Me): How about have the threat mean that when he opens the door it creaks open, alerting anything that might be in the facility that someone is at the lift shaft?

GM: Even better, sounds great.

And then of course we have an ambush encounter waiting for us as we climb down the lift shaft.

As a player, I'm probably far more dangerous to my party than my GM with regards to threats/despairs.

Player: OK GM, I rolled a success and 3 threat when making the mechanics check to do the manual override to open the turbo lift door in the unpowered and abandoned facility.

GM: Good, well, the success means you got the door open, and three threat...You're all a bit annoyed by how long it took, setback for everyones next check

Player (Me): How about have the threat mean that when he opens the door it creaks open, alerting anything that might be in the facility that someone is at the lift shaft?

GM: Even better, sounds great.

And then of course we have an ambush encounter waiting for us as we climb down the lift shaft.

Players are their own worst enemies. The sooner they embrace this truth, the more fun will be had by all