Branching Dialogue Trees

A dialogue tree is a graph. Each node holds a line of NPC speech and a list of player responses; picking one moves you to another node, and some nodes set flags that alter what is available later or elsewhere. Early implementations used typed keywords rather than menus, so the branching was hidden inside a vocabulary the player had to assemble from rumours, letters and overheard names.

Origin Systems built the technique into Ultima IV: Quest of the Avatar in 1985 because the game needed to test the player's ethics, and a test demands questions with answers. Conversation was the only interface capable of asking. Attribution is genuinely contested: text adventures had accepted typed input for years, and other role-playing games of the period experimented with keyword talk, so Ultima IV is best read as the point where dialogue became a designed structure rather than a parser trick.

Consequences run in two directions. Writing became combinatorial, so cost grew with every branch, and studios learned to fake width with options that quietly converge inside a single scene. Set against that, dialogue trees gave the medium a way to make players responsible for what their character says, which is the precondition for reputation systems, companion relationships and endings that actually differ. Critics have argued ever since that picking from a list is not the same as speaking.