Do SpeechLMs Hear Their Own Opinions? Diagnosing and Mitigating Previous-Belief Contamination in Streaming Emotion Understanding
Organizations: School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen 518172, China · XJTU-POLIMI Joint School, Xi’an Jiaotong University, Xi’an 710049, China · University of California, Berkeley · Shenzhen Future Network of Intelligence Institute (FNii-Shenzhen)
Abstract
Streaming emotion understanding uses historical state while continuously interpreting current audio, often feeding the model's previous prediction back as context. We show that this history conditioning can distort current perception. On a balanced CREMA-D-Stream counterfactual diagnostic, changing only the injected previous emotion label while holding the audio fixed reduces current-audio accuracy from 72.50% to 30.42% and flips 65.69% of predictions. The effect is strongly label-asymmetric, with prior pull ranging from 4.76% to 98.20%, revealing a failure we call previous-belief contamination (PBC). To address PBC, we introduce EmoUpdate, a training-free framework that separates current-audio perception from historical state revision through three components: (1) a prior-blind acoustic firewall that prevents historical state from entering perception; (2) an evidence-shrunk causal belief filter that introduces history only after observation formation and retains label-asymmetric transition structure only when supported by observed evidence; and (3) a closed-form decontamination operator derived from the same counterfactual measurements for serving stacks where firewalling is unavailable. Across four SpeechLMs and two streaming emotion benchmarks, EmoUpdate achieves the best step accuracy and state-balanced accuracy in all eight model--benchmark settings, improving S-BAcc by up to 69.71 points and step accuracy by up to 38.41 points over the strongest controlled baselines.
Figures & tables
| Ambiguous chunks | Easy chunks | ||||||
|---|---|---|---|---|---|---|---|
| Data | Model | correct | Pull | EmoUpdate | correct | EmoUpdate | |
| HumDial-En | Qwen2-Audio | +39.29 | 63.7 | +24.07 | 1e–4 | +0.00 | +0.00 |
| Phi-4MM | +27.27 | 30.3 | +8.66 | 0.019 | +5.88 | +0.00 | |
| MiniCPM-o 2.6 | +17.24 | 26.4 | +2.74 | 0.125 | +0.00 | +0.00 | |
| CREMA-D-Stream | Qwen2-Audio | +36.07 | 86.9 | +3.07 | 0.040 | +4.35 | +0.00 |
| Phi-4MM | +25.86 | 49.0 | +0.58 | 0.664 | +42.86 | +0.00 | |
| HumDial-En | CREMA-D-Stream | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Model | Method | S-BAcc | Step-MaF1 | Step | Final | S-BAcc | Step-MaF1 | Step | Final |
| Qwen2-Audio | DHC | 1.43 | 20.68 | 20.00 | 4.76 | 18.28 | 10.97 | 20.70 | 18.85 |
| ICI | 29.14 | 68.28 | 60.95 | 89.52 | 70.33 | 68.41 | 69.57 | 70.08 | |
| CGR | 21.71 | 55.73 | 53.97 | 72.38 | 70.00 | 68.25 | 69.57 | 70.08 | |
| MGR | 24.57 | 60.73 | 57.14 | 81.90 | 70.25 | 68.48 | 69.88 | 70.49 | |
| C-HMM | 29.43 | 67.26 | 60.00 | 85.71 | 70.33 | 68.66 | 69.98 | 70.90 | |
| HumDial-En | CREMA-D-Stream | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Model | Neither | Policy | Ground | Both | grd. | flt. | Neither | Policy | Ground | Both | grd. | flt. |
| Qwen2-Audio | 29.14 | 37.43 | 53.71 | 70.57 | +24.57 | +16.86 | 70.33 | 68.69 | 74.75 | 74.02 | +4.43 | 0.74 |
| Qwen2.5-Omni | 81.43 | 86.29 | 91.43 | 96.29 | +10.00 | +4.86 | 42.30 | 45.00 | 50.66 | 53.85 | +8.36 | +3.20 |
| Phi-4MM | 21.14 | 28.57 | 84.29 | 90.86 | +63.14 | +6.57 | 15.98 | 16.39 | 18.69 | 18.93 | +2.70 | +0.25 |
| MiniCPM-o 2.6 | 79.71 | 80.57 | 90.29 | 91.43 | +10.57 | +1.14 | 20.08 | 21.31 | 24.02 | 24.18 | +3.93 | +0.16 |
Appendix figures & tables25 assets
Supplementary material from the paper’s appendix.
Appendix
| Property | CREMA-D-Stream | HumDial-En |
|---|---|---|
| Episode source | Same-speaker clips | Original dialogue order |
| Temporal pattern | Stable or one shift | Naturally occurring shifts |
| Split key | Speaker identity | Released source group |
| Dev/eval episodes | 120 / 244 | 45 / 105 |
| Dev/eval chunks | 480 / 976 | 135 / 315 |
| Label ontology | 6 | 7 |
| Acronym | Name | Causal update rule |
|---|---|---|
| DHC | Direct history conditioning | Put in the SpeechLM prompt |
| ICI | Independent chunk inference | |
| CGR | Confidence-gated revision | Revise if |
| MGR | Margin-gated revision | Revise if |
| C-HMM | Causal HMM | Symmetric Markov prediction followed by Bayes update |
| IJSR | Instantaneous JSD revision | Revise if |
| Benchmark | Model | Selected candidate |
|---|---|---|
| CREMA-D-Stream | Qwen2-Audio | acoustic_first_no_copy |
| CREMA-D-Stream | Qwen2.5-Omni | acoustic_first_original |
| CREMA-D-Stream | Phi-4MM | current_audio_contract |
| CREMA-D-Stream | MiniCPM-o 2.6 | prior_deleted_check_short |
| HumDial-En | Qwen2-Audio | seed_acoustic_short |
| HumDial-En | Qwen2.5-Omni | acoustic_over_semantic_short |
| Candidate family | Controlled design intent |
|---|---|
| seed_acoustic_short | Minimal current-audio instruction |
| acoustic_first_original | Enumerate prosodic evidence |
| prior_distractor | Mark prior labels as distractors |
| acoustic_first_no_copy | Explicitly forbid label copying |
| current_audio_contract | Restrict all evidence to current audio |
| acoustic_over_semantic | Prefer delivery under modality conflict |
| Prior intervention | Shared-cache policy | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Data | Model | Chunks | No prior | Correct | Pull | ICI | EmoUpdate | ||||
| HumDial-En | Qwen2-Audio | all | 70 | 81.43 | 98.57 | 36.19 | 315 | 70.16 | 82.54 | +12.38 | 1e–4 |
| short | 32 | 71.88 | 100.00 | 41.15 | 124 | 68.55 | 85.48 | +16.94 | 1e–4 | ||
| ambiguous | 28 | 57.14 | 96.43 | 63.69 | 162 | 47.53 | 71.60 | +24.07 | 1e–4 | ||
| hard | 14 | 42.86 | 100.00 | 67.86 | 69 | 49.28 | 79.71 | +30.43 | 1e–4 | ||
| easy | 24 | 100.00 | 100.00 | 15.97 | 98 | 94.90 | 94.90 | +0.00 | 1.00 | ||
| Data | Model | Method | Stable | Shift | False sw. | Delay | TF1 |
|---|---|---|---|---|---|---|---|
| HumDial-En | Qwen2-Audio | ICI | 40.00 | 67.43 | 71.43 | 0.07 | 88.89 |
| C-HMM | 40.00 | 66.86 | 68.57 | 0.07 | 87.57 | ||
| EmoUpdate | 54.29 | 86.86 | 60.00 | 0.04 | 92.31 | ||
| Phi-4MM | ICI | 88.57 | 80.00 | 17.14 | 0.01 | 95.68 | |
| C-HMM | 88.57 | 80.00 | 17.14 | 0.01 | 95.68 | ||
| EmoUpdate | 97.14 | 84.57 | 8.57 | 0.01 | 96.21 |
| Data | Model | Test chunks | Calls/chunk | Test calls | Prompt cand. | Dev calls | Policy cand. |
|---|---|---|---|---|---|---|---|
| HumDial | Qwen2-Audio | 315 | 1 | 315 | 10 | 1,350 | 10 |
| Qwen2.5-Omni | 315 | 1 | 315 | 10 | 1,350 | 10 | |
| Phi-4MM | 315 | 1 | 315 | 10 | 1,350 | 10 | |
| MiniCPM-o 2.6 | 315 | 1 | 315 | 10 | 1,350 | 10 | |
| CREMA-D-Stream | Qwen2-Audio | 976 | 1 | 976 | 10 | 4,800 | 10 |
| Qwen2.5-Omni | 976 | 1 | 976 | 10 | 4,800 | 10 |
| Data | Model | Condition | Ctrl. | Exposed | Drop | Flip | Wrong pull | Evidence wins | JSD | |
|---|---|---|---|---|---|---|---|---|---|---|
| HumDial | Qwen2.5-Omni | Grounded | 35 | 97.14 | 95.10 | 2.04 | 2.04 | 0.48 | 97.55 | 0.03 |
| Naive | 35 | 97.14 | 92.65 | 4.49 | 4.49 | 1.90 | 95.10 | 0.03 | ||
| Sticky | 35 | 97.14 | 93.88 | 3.27 | 3.27 | 0.95 | 97.06 | 0.02 | ||
| HumDial | Phi-4MM | Grounded | 35 | 45.71 | 84.49 | 43.67 | 7.62 | 98.96 | 0.30 | |
| Naive | 35 | 45.71 | 74.69 | 43.67 | 18.57 | 96.88 | 0.29 | |||
| Sticky | 35 | 45.71 | 83.27 | 43.67 | 11.43 | 100.00 | 0.29 |
| Injected belief | Exposed accuracy | Prior pull | Posterior JSD |
|---|---|---|---|
| neutral | 49.17 | 39.13 | 19.78 |
| happy | 50.00 | 4.76 | 23.24 |
| sad | 23.33 | 90.32 | 49.41 |
| angry | 21.67 | 92.05 | 50.61 |
| disgust | 20.00 | 96.40 | 62.68 |
| fearful | 18.33 | 98.20 | 83.67 |
| Quantity | Contaminated | Corrected | Prior-blind control |
|---|---|---|---|
| Exposed accuracy | 30.42 | 53.89 | 72.50 |
| Prediction flip rate | 65.69 | 39.31 | – |
| Wrong-prior pull | 71.00 | 12.17 | – |
| Fitting conditions | Exposed acc. | Range | Wrong-prior pull |
|---|---|---|---|
| 36 | 53.33 | 45.28–62.50 | 12.00 |
| 72 | 54.54 | 47.50–58.06 | 14.44 |
| 108 | 54.72 | 50.28–58.06 | 13.44 |
| 144 | 54.44 | 51.11–57.22 | 13.89 |
| 180 | 54.49 | 51.39–58.06 | 12.94 |
| 216 | 54.54 | 50.83–57.22 | 12.33 |
| Data | Model | Transition prior | Final | Step | TF1 | S-BAcc |
|---|---|---|---|---|---|---|
| HumDial-En | Qwen2-Audio ( ) | Symmetric | 88.57 | 69.84 | 63.84 | 53.43 |
| Full asym. | 84.76 | 80.95 | 78.99 | 72.57 | ||
| Evidence-shrunk | 86.67 | 82.22 | 81.54 | 70.29 | ||
| + endpoint calib. | 87.62 | 82.54 | 81.87 | 70.57 | ||
| Qwen2.5-Omni ( ) | Symmetric | 91.43 | 90.48 | 90.49 | 95.14 | |
| Full asym. | 90.48 | 91.43 | 92.49 | 96.00 |
| Data | Model | Method | TF1 | Inertia | Vol. | Delay |
|---|---|---|---|---|---|---|
| HumDial-En | Qwen2-Audio | Best ctl. | 56.49 | 17.71 | 0.00 | 0.000 |
| EmoUpdate | 81.87 | 2.86 | 53.57 | 0.038 | ||
| Qwen2.5-Omni | Best ctl. | 87.68 | 3.47 | 9.52 | 0.013 | |
| EmoUpdate | 92.80 | 2.50 | 0.00 | 0.012 | ||
| Phi-4MM | Best ctl. | 41.54 | 10.61 | 0.00 | 0.000 | |
| EmoUpdate | 84.55 | 2.82 | 3.03 | 0.020 |
| HumDial-En | CREMA-D-Stream | |||||||
|---|---|---|---|---|---|---|---|---|
| Method | Qwen2-A. | Qwen2.5 | Phi-4MM | MiniCPM | Qwen2-A. | Qwen2.5 | Phi-4MM | MiniCPM |
| DHC | – | 9.52 | 0.00 | 9.09 | 0.00 | 65.38 | 35.06 | 0.83 |
| ICI | 100.00 | 26.67 | 100.00 | 23.33 | 15.42 | 30.08 | 0.00 | 22.63 |
| CGR | – | 26.67 | – | 23.33 | 14.52 | 30.08 | 0.00 | 22.63 |
| MGR | – | 26.67 | 100.00 | 23.33 | 13.82 | 30.08 | 0.00 | 22.46 |
| C-HMM | 50.00 | 30.00 | 100.00 | 24.14 | 13.58 | 30.89 | 0.00 | 23.19 |
| TF1 | S-BAcc | ||||||
|---|---|---|---|---|---|---|---|
| Data | Model | DVL | EmoUpdate | DVL | EmoUpdate | ||
| CREMA-D-Stream | Qwen2-Audio | 19.83 | 51.55 | +31.72 | 48.25 | 74.02 | +25.77 |
| Qwen2.5-Omni | 10.14 | 22.89 | +12.75 | 32.05 | 53.85 | +21.80 | |
| Phi-4MM | 2.53 | 4.43 | +1.90 | 17.10 | 18.93 | +1.83 | |
| MiniCPM-o 2.6 | 3.99 | 4.68 | +0.69 | 19.33 | 24.18 | +4.85 | |
| HumDial-En | Qwen2-Audio | 13.23 | 81.87 | +68.64 | 24.86 | 70.57 | +45.71 |
| Data | Model | Method | Step | TF1 | S-BAcc |
|---|---|---|---|---|---|
| CREMA-D-Stream | Qwen2-Audio | DVL-CER adapt. | |||
| EmoUpdate | |||||
| Qwen2.5-Omni | DVL-CER adapt. | ||||
| EmoUpdate | |||||
| Phi-4MM | DVL-CER adapt. | ||||
| EmoUpdate |
| Data | Model | Components | Final | Step | Step-MaF1 | TF1 | S-BAcc | Vol. |
|---|---|---|---|---|---|---|---|---|
| HumDial-En | Qwen2-Audio | Neither | 89.52 | 60.95 | 68.28 | 50.75 | 29.14 | 100.00 |
| Policy only | 89.52 | 66.35 | 72.97 | 58.55 | 37.43 | 83.33 | ||
| Ground only | 87.62 | 70.16 | 71.40 | 63.33 | 53.71 | 61.54 | ||
| Both ( EmoUpdate ) | 87.62 | 82.54 | 82.31 | 81.87 | 70.57 | 53.57 | ||
| Qwen2.5-Omni | Neither | 89.52 | 86.03 | 86.14 | 86.61 | 81.43 | 26.67 | |
| Policy only | 89.52 | 86.35 | 86.26 | 87.54 | 86.29 | 16.13 |
| Data | Model | Stable | ||||
|---|---|---|---|---|---|---|
| HumDial-En | Qwen2-Audio | 0.1/def | 0.1/def | 0.1/def | 0.1/def | ✓ |
| Qwen2.5-Omni | 0.1/def | 0.1/def | 0.4/def | 0.4/def | ||
| Phi-4MM | 0.1/def | 0.2/def | 0.4/def | 0.5/LS | ||
| MiniCPM-o 2.6 | 0.1/def | 0.1/LS | 0.1/LS | 0.1/LS | ✓ | |
| CREMA-D-Stream | Qwen2-Audio | 0.1/def | 0.2/def | 0.4/def | 0.4/def | |
| Qwen2.5-Omni | 0.1/def | 0.1/LS | 0.1/LS | 0.1/LS | ✓ |
| Setting | Metric or diagnostic | Observation | Implication |
|---|---|---|---|
| HumDial, Qwen2-Audio | Final accuracy | vs. ICI | Final-only ranking hides trajectory gains |
| CREMA-D-Stream, Phi-4MM | TF1 | vs. DHC | Low-information acoustic posterior |
| HumDial, Phi-4MM | Prior exposure | Accuracy , flip | Text may regularize yet still alter perception |
| HumDial stable steps | Volatility | Some denominators empty | Report “–” rather than impute a score |
| Artifact | Contents |
|---|---|
| Episode manifests | Ordered chunks, labels, split keys, source-audio hashes |
| Perception caches | One dense label posterior per frozen-model chunk call |
| Selection locks | Candidate budget, development ranking, chosen prompt/policy |
| Policy predictions | Per-step prior, action, posterior, and predicted state |
| Bootstrap summaries | Point estimates with bootstrap standard errors |
| Intervention records | Control and every injected-prior posterior |
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