Organizations: University of Technology Sydney · Alibaba Cloud Computing · Stony Brook University · East China Normal University · Shanghai Jiao Tong University · The Education University of Hong Kong
Multimodal large language models (MLLMs) have demonstrated remarkable progress on cross-modal reasoning tasks, yet they continue to suffer from hallucinations in long-chain reasoning processes. In this work, we revisit hallucination in MLLMs from the perspective of reasoning generation dynamics. We argue that entropy is not merely a static measure of uncertainty but a structured signal that reflects how modality information is integrated throughout decoding. Through systematic analysis, we identify two characteristic entropy patterns associated with hallucination behaviors: (1) a generally high-confidence regime corresponds to premature convergence to inappropriate multimodal interactions; and (2) local abrupt entropy transitions are associated with reasoning instability and hallucination onset. Building on these observations, we propose an entropy-aware self-introspective framework for MLLM reasoning. Our method continuously tracks entropy dynamics during decoding and performs targeted visual re-alignment when suspicious hallucination states are detected, encouraging the model to re-examine salient visual evidence at critical reasoning stages. Extensive experiments across six multimodal reasoning benchmarks spanning nine distinct evaluation settings demonstrate that our approach delivers robust improvements in reasoning accuracy and hallucination robustness, while providing new insights into the generation dynamics underlying MLLM failures. The code is available at: https://github.com/jden4524/SelfRetrospectiveDecoding.
Figures & tables
Figure 1: Comparison of generation dynamics between correct and incorrect multimodal reasoning trajectories. (a) Average reasoning entropy across the generation process over samples, where correct predictions consistently maintain higher entropy than incorrect ones. (b) Evolution of visual attention during CoT generation, showing that correct reasoning trajectories preserve stronger visual grounding at the early stage of reasoning, while incorrect trajectories exhibit progressively weakened but still higher attention to visual evidence. Shaded regions denote standard deviations.
Figure 2: A case study illustrating hallucination emergence during MLLM reasoning. The left panel shows entropy over generated tokens, while the right panel visualizes the corresponding visual attention patterns at selected reasoning steps (P5–P8). The gray region denotes the span of incorrect generation. Hallucinated reasoning coincides with sharp entropy spikes (P8) and progressively strong but diffused visual attention. More examples can be found in Appendix A .
ΔH @onset
Low-entropy duration
Spike frequency
Max ΔH
Correct ( n=465 )
0.012
17.6
0.085
1.762
Hallucinated ( n=763 )
0.245
21.4
0.101
1.974
p -value
4×10−4
<10−35
<10−9
<10−16
Table 1: Population-level entropy statistics on 1,228 VQA trajectories (Qwen3-VL-8B). ΔH @onset is the mean entropy change at the aligned hallucination onset ( p=0 ); the remaining columns are per-trajectory statistics. p -values are from two-sided Mann–Whitney U tests.
Figure 3: Framework overview of the proposed SEED . The figure presents three parts: (a) A standard MLLM architecture processes system instructions and visual tokens through stacked decoder layers to perform multimodal reasoning. (b) A self-introspective mechanism monitors token-level entropy dynamics throughout the decoding process, capturing locally important spikes that signal shifts in reasoning dynamics. (c) When both detection conditions are met, our method performs an attention intervention during decoding to rectify the multimodal interaction. We refer to this process as Visual Attention Re-alignment Decoding.
Method
Multimodal Reasoning & Understanding
Summary Δ (%) / improved
VStar ↑
MMVP ↑
VisOnly s ↑
VisOnly r ↑
M 3 CoT ↑
Qwen3-VL-8B
73.82
76.23
42.20
54.60
78.21
–
+ VCD
54.45( -19.4 )
80.00( +3.8 )
42.57( +0.4 )
55.71( +1.1 )
77.68( -0.5 )
−2.93 / 3/5
+ MemVR
74.87( +1.0 )
80.67( +4.4 )
41.86( -0.3 )
54.44( -0.2 )
77.68( -0.5 )
+0.89 / 2/5
+ SEED (Ours)
83.25( +9.4 )
76.33( +0.1 )
47.00( +4.8 )
54.37( -0.2 )
79.97( +1.8 )
+3.17 / 4/5
Qwen3-VL-4B
68.06
76.33
42.14
52.22
76.79
–
Table 2: Comparisons across general reasoning benchmarks. The summary column reports the macro-average change in percentage points and the number of strictly positive changes over available settings. Base MLLMs use the default CoT setting.
Method
Multimodal Hallucination
Summary Δ (%) / improved
HalluBench ↑
POPE-R ↑
POPE-P ↑
POPE-A ↑
Qwen3-VL-8B
58.50
90.25
87.53
86.42
–
+ VCD
56.24( -2.3 )
91.67( +1.4 )
87.03( -0.5 )
86.30( -0.1 )
−0.37 / 1/4
+ MemVR
55.87( -2.6 )
90.63( +0.4 )
88.12( +0.6 )
86.85( +0.4 )
−0.31 / 3/4
+ SEED (Ours)
59.28( +0.8 )
97.39( +7.1 )
90.94( +3.4 )
85.07( -1.3 )
+2.49 / 3/4
Qwen3-VL-4B
54.80
90.92
88.64
87.96
–
Table 3: Comparisons across hallucination benchmarks. The summary column reports the macro-average change in percentage points and the number of positive changes over available settings. Base MLLMs use the default CoT setting.
Attention Intervention Strategy
Qwen3-VL-8B
Qwen3-VL-4B
Accuracy ↑
Efficiency ↑
Accuracy ↑
Efficiency ↑
None (baseline)
78.21
0.20
76.79
0.22
+ Equal attention
80.24(+2.0)
0.05( × 0.25)
78.02(+1.2)
0.07( × 0.32)
+ Truncated SVD Project
54.28(-23.9)
0.17( × 0.85)
50.23(-26.6)
0.18( × 0.82)
+ ViT attention intervene
60.32(-17.9)
0.15( × 0.75)
55.36(-21.4)
0.16( × 0.73)
+ SEED (Ours)
79.97 (+1.8)
0.19( × 0.95)
78.03 (+1.2)
0.21( × 0.95)
Table 4: Comparison of attention intervention strategies across backbones on M 3 CoT ( Chen et al., 2024 ) . Each backbone is evaluated in terms of accuracy and efficiency (instance/s). All hyperparameters are kept consistent. The best and second-best results are highlighted in green and blue, respectively.
Appendix figures & tables10 assets
Supplementary material from the paper’s appendix.
Appendix
Figure 4: More examples illustrating hallucination emergence during MLLM reasoning. The left panel shows entropy over generated tokens, while the right panel visualizes the corresponding visual attention patterns at selected reasoning steps. The gray region denotes the span of incorrect generation. Hallucinated reasoning coincides with regions containing sharp entropy spikes and increasingly strong yet diffuse visual attention.
Figure 5: Statistical analysis of wrong reasoning span sizes. The reasoning processes of 270 VQA samples are recorded. Results show that wrong reasoning claims concentrate in the first 20% of the generation process.
p
−20∼−11
−5
−4
−3
−2
−1
0
+1
+2∼+5
+6∼+20
Hallucinated
0.0020
0.0560
0.0011
0.0188
− 0.0423
0.0065
0.2447
− 0.1728
− 0.0227 ∼ 0.0081
− 0.0025
Correct
0.0007
0.0119
0.0140
− 0.0010
− 0.0109
0.0047
0.0117
− 0.0125
− 0.0404 ∼ 0.0265
0.0007
Appendix
Table 5: Mean token-to-token entropy change ΔH aligned to the hallucination onset ( p=0 ). For ranges, the mean over the range (or its min–max) is reported.
Method
Latency ↓ (ms/token)
Throughput ↑ (instance/s)
Time Cost ↓ (min)
Greedy
3.30 ( × 1.00)
0.941 ( × 1.00)
20.0 ( × 1.00)
OPERA
14.28 ( × 4.33)
0.224 ( × 0.24)
85.0 ( × 4.25)
VCD
5.08 ( × 1.54)
0.598 ( × 0.63)
31.5 ( × 1.58)
MemVR
8.47 ( × 2.57)
0.359 ( × 0.38)
52.5 ( × 2.63)
SEED
3.45 ( × 1.05)
0.897 ( × 0.95)
21.0 ( × 1.05)
Appendix
Table 6: Performance comparison of SOTA methods and SEED in latency, throughput, and time cost. All methods are built on the Qwen3-VL-8B-Instruct backbone. The experiment is conducted on M3CoT and all models are prompted to generate CoT. Note that all results are evaluated under an inference acceleration framework.
Transition
Interpretation
Count
Rate
Trigger ratio
Avg. triggers
Avg. span
Correct → Wrong
Harmful intervention
454
15.13%
46.26%
2.04
7.95
Wrong → Correct
Successful correction
408
13.60%
43.38%
2.20
8.69
Wrong → Wrong
Unresolved error
729
24.30%
60.22%
2.93
11.84
Appendix
Table 7: Paired transition analysis between the base model and SEED on POPE-Adversarial with Llama-3.2-11B-Vision.
Figure 6: Hyperparameter analysis of injection ratios (left) and entropy threshold (right).
α
0.40
0.45
0.50
0.70
78.30 (+0.09)
78.79 (+0.58)
79.89 (+1.68)
78.21 (+0.00)
τrise
0.225
0.250
0.275
0.300
78.42 (+0.21)
79.89 (+1.68)
79.20 (+0.99)
78.53 (+0.32)
t1
40
50
60
70
79.12 (+0.91)
79.48 (+1.27)
79.89 (+1.68)
78.91 (+0.70)
Appendix
Table 8: Hyperparameter sensitivity on M 3 CoT with Qwen3-VL-8B (base model: 78.21). Gains over the base model are shown in parentheses.
Figure 7: Additional hyperparameter analysis of the entropy threshold, injection ratio, and the start and end steps of the monitoring window.
Figure 8: A case study illustrating that SEED not only improves final answer accuracy but also produces more reliable intermediate reasoning steps. Hallucinated content is highlighted in purple, while correct reasoning is highlighted in yellow.
Figure 9: Full analysis on one example to demonstrate the effectiveness of SEED. The hallucination related text is highlighted in yellow and the statement related to correct reasoning is highlighted in blue.
University of Science and Technology of China, Hefei, China · Huawei Foundation Model Department, Shanghai, China · The Chinese University of Hong Kong, Hong Kong, China +1