ResearchResearch paperLarge Language Models · Speech & Audio · Robotics & Embodied AI1 source · Oct 6, 2026

Steering Follows Geometry, Not Labels: Emotion Directions in a Full-Duplex Speech Model

We study emotion steering in Moshi, a fully open sourced full-duplex speech language model, across four emotions, using mean-difference activation steering, which costs only a few vector additions per frame and no retraining.

Key points

  • Full-duplex voice agents need to modulate emotion and delivery during real-time conversations, when de-escalating a complaint, carrying urgency in dispatch, softening a clinical result.
  • Emotion and delivery control is well studied for TTS and turn based models through prompt-conditioned synthesis, reference-conditioned synthesis and activation steering; PersonaPlex controls identity in a duplex model but not affect.
  • We show that emotion is linearly decodable from Moshi's residual stream, but activation steering is only partially achievable, and unevenly so; as happy, angry and surprise steer towards a shared direction while sad is distinctly steerable.
  • We also show that the shared component across the three emotions cannot simply be projected away from all the emotions equally.

Sources (1)

  • [1]Steering Follows Geometry, Not Labels: Emotion Directions in a Full-Duplex Speech Model
    arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 6, 03:29 PM
    We study emotion steering in Moshi, a fully open sourced full-duplex speech language model, across four emotions, using mean-difference activation steering, which costs only a few vector additions per frame and no retraining.
    Full-duplex voice agents need to modulate emotion and delivery during real-time conversations, when de-escalating a complaint, carrying urgency in dispatch, softening a clinical result.

Extractive summary: sentences quoted from the sources.

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