@inproceedings{naber-etal-2026-probing,
    title = "Probing Discrete Speech Tokens of Spoken Language Models",
    author = "Naber, Sven  and
      Koch, Julia  and
      Singh, Pranav  and
      Saponaro, Alberto  and
      Karagianni, Ioanna  and
      Vu, Ngoc Thang",
    editor = "Piperidis, Stelios  and
      Bel, N{\'u}ria  and
      van den Heuvel, Henk  and
      Ide, Nancy  and
      Krek, Simon  and
      Toral, Antonio",
    booktitle = "Proceedings of the Fifteenth Language Resources and Evaluation Conference",
    month = may,
    year = "2026",
    address = "Palma de Mallorca, Spain",
    publisher = "ELRA Language Resource Association",
    url = "https://preview.aclanthology.org/paragraph-normalization/2026.lrec-1.184/",
    doi = "10.63317/4d4kttgdydde",
    pages = "2344--2354",
    abstract = "This paper presents a framework for systematic probing of discrete speech token representations in spoken language models (SLMs). We propose three complementary components: a distributional divergence analysis testing whether an attribute is reflected in token usage, token-based classifiers to quantify recoverability and an attribute-conditioned representation analysis revealing phonetic attribute realizations. As a demonstration we apply these probes to tokenizer outputs and model generations from CosyVoice2 and SparkTTS on LibriTTS-R and VCTK. We find that gender is encoded in their respective tokens but in different forms - the signal is more stable across stages and datasets in CosyVoice2, whereas SparkTTS shows weaker cross-stage consistency and stronger pause/prosody-related effects. Exploratory probes of valence, arousal, and dominance are weaker and less consistent. These results show that discrete speech tokens retain speaker-related information in different ways across architectures and that the proposed framework provides an interpretable basis for comparing token representations across spoken language modeling pipelines."
}