Worthplaying has an E3-based preview of Mass Effect:
As with its Halo 3 and Fable 2 meetings, our meeting with Microsoft for Mass Effect was highly focused, with much of the presentation dealing with the games superb-looking conversation system. Previous BioWare titles have allowed players to dictate their responses to A.I.-instigated queries, but Mass Effect removes the rough edges, presenting such discussions in a highly cinematic way, similar to that of a film or a pre-rendered cut-scene. Using the in-game engine, the camera shifts to an up-close perspective during a discussion, allowing players to focus on facial expressions and attempt to interpret body language.
But conversations in Mass Effect are more about what you say than what you see. As the scene unfolds, conversational options will appear around a small circle on the bottom portion of the screen, allowing the player to choose a response while the NPC is talking. Where previous systems most resembled the exchange of instant messages, discussions in Mass Effect come as close to the ebb and flow of a verbal conversation as we’ve seen in a game. Choices made in the midst of a conversation not only affect the direction of that particular dialogue, but may also lead to decisions that will affect the rest of the game.