The Fallout 4 dialogue system is a radical departure from previous titles, featuring a voiced protagonist and a different response selection interface.
When talking to a non-player character, the player will be able to select one of four responses, arranged in a cross pattern. Rather than displaying the full response, each option only has a brief description, often a single world, summarizing the attitude of the response.
The upper selection is usually responsible for questions and other queries, while the left, right, and down options are assigned to different responses, usually sarcasm, yes, no, or persuasion.
If the player does not choose a dialogue option for certain period of time, NPCs will typically have unique dialogue that plays. Look away from an NPC while in conversation will allow the player to stop talking without choosing an available dialogue option.
The biggest change comes from the fact that Fallout 4 does away with skill or perk checks in dialogue. Instead, all persuasion attempts depend entirely on the character's Charisma and applicable perks, like Ladykiller or Black Widow. Persuasion checks are colored from yellow for easy, orange for difficult, and red for hard.
Alternatives to persuasion include learning certain facts in advance. For example, giving Mama Murphy drugs (morality of giving such substances to elderly people aside) will allow the player to learn responses that will allow to bypass difficult combat sequences in the main quest, such as Skinny Malone or Z2-47.