Abstract
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 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. 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.
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Publication details
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- Open access
- Green open access
Cite this article
APA 7
Kuli, P. (2026). Steering Follows Geometry, Not Labels: Emotion Directions in a Full-Duplex Speech Model. https://omanscience.com/en/articles/steering-follows-geometry-not-labels-emotion-directions-in-a-full-duplex-speech-model
MLA 9
Kuli, Pulak. "Steering Follows Geometry, Not Labels: Emotion Directions in a Full-Duplex Speech Model." https://omanscience.com/en/articles/steering-follows-geometry-not-labels-emotion-directions-in-a-full-duplex-speech-model.
Chicago (author–date)
Kuli, Pulak. 2026. "Steering Follows Geometry, Not Labels: Emotion Directions in a Full-Duplex Speech Model." https://omanscience.com/en/articles/steering-follows-geometry-not-labels-emotion-directions-in-a-full-duplex-speech-model.
Harvard
Kuli, P. (2026) 'Steering Follows Geometry, Not Labels: Emotion Directions in a Full-Duplex Speech Model', Available at: https://omanscience.com/en/articles/steering-follows-geometry-not-labels-emotion-directions-in-a-full-duplex-speech-model.
Vancouver
Kuli P. Steering Follows Geometry, Not Labels: Emotion Directions in a Full-Duplex Speech Model. https://omanscience.com/en/articles/steering-follows-geometry-not-labels-emotion-directions-in-a-full-duplex-speech-model
IEEE
P. Kuli, "Steering Follows Geometry, Not Labels: Emotion Directions in a Full-Duplex Speech Model," https://omanscience.com/en/articles/steering-follows-geometry-not-labels-emotion-directions-in-a-full-duplex-speech-model.