S⌃4: Operationalizing Speech Act Theory for Strategic Semi-Structured Psychiatric Interview

Psychiatric interviewing is a strategic, goaloriented interaction that requires proactively steering the conversation to elicit latent information. However, existing methods often degenerate into rigid interrogation or aimless chitchat due to a lack of strategic planning. In this work, we introduce S 4 , a comprehensive framework grounded in Speech Act Theory, modeling the interview as a unified process of internal strategy (Illocution and Perlocution) and external realization (Locution). We synthesize a large-scale dataset with fine-grained psychiatric speech act annotations. Trained on this data, S 4 employs reinforcement learning driven by long-term therapeutic effects to optimize the strategic chaining of atomic acts, aiming to maximally elicit information and maintain patient engagement. Experiments demonstrate that S 4 significantly outperforms baselines, validating the effectiveness of our effectdriven strategic modeling. Action (A) Sample Locution (L) Definition & Intended Perlocution (P) I. Information Seeking (Directives: Eliciting Disclosure) Explore "How have you been sleeping?" Solicit Narrative: Ask open-ended questions to elicit detailed disclosure and expand symptom scope. Probe "Could you tell me more about that?" Deepen Inquiry: Follow up on ambiguity to clarify details and deepen focus. Confirm "Do you feel this way every day?" Pinpoint Fact: Ask closed-ended questions to verify diagnostic criteria. Clarify "By 'fatigue', I mean tiredness." Resolve Confusion: Provide explanations to align cognition and correct misunderstandings. II. Affective Regulation (Expressives: Modifying State) Validate "That sounds incredibly hard." Affirm Emotion: Acknowledge patient distress to lower defensiveness and build trust. Support "I understand. Please go on." Maintain Flow: Use back-channeling to demonstrate active listening and boost efficacy. Ease "Do you have any hobbies?" Reduce Tension: Engage in non-clinical conversation to de-escalate anxiety and humanize the agent. III. Interview Management (Representatives: Setting Frame) Initiate "Hi, I'm your AI counselor." Set Frame: Establish professional boundaries and the purpose of the session. Conclude "Thanks for sharing. Take care." Ensure Closure: Formally end the session to provide a safe exit and consolidation.