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arxiv: 2412.13050 · v2 · submitted 2024-12-17 · 💻 cs.LG · cs.AI· cs.CL· cs.CV· cs.SD· eess.AS

Modality-Inconsistent Continual Learning of Multimodal Large Language Models

Pith reviewed 2026-05-23 06:44 UTC · model grok-4.3

classification 💻 cs.LG cs.AIcs.CLcs.CVcs.SDeess.AS
keywords continual learningmultimodal large language modelscatastrophic forgettingmodality inconsistencyknowledge distillationpseudo targetstask-type shift
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The pith

MoInCL counters catastrophic forgetting in MLLMs when both input modalities and task types shift across training stages.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper defines a new continual learning problem, MICL, in which multimodal large language models must handle sequences of tasks whose input types (image, audio, video) and output types (captioning versus question-answering) both change. Existing methods fail because modality switches and task-type switches each trigger forgetting of earlier capabilities. MoInCL therefore adds a Pseudo Targets Generation Module that creates synthetic targets for previously seen modalities under new task formats, and an Instruction-based Knowledge Distillation step that keeps the model responsive to old modalities when new ones arrive. Experiments on a six-task benchmark demonstrate that these two additions together produce higher average performance than standard and state-of-the-art continual-learning baselines.

Core claim

MICL is the continual-learning setting that jointly introduces modality inconsistency and task-type inconsistency; MoInCL mitigates the resulting forgetting by generating pseudo targets for old modalities under new task instructions and by distilling knowledge from old-modality instructions, yielding measurable gains on the six-task MICL benchmark over representative continual-learning methods.

What carries the argument

The Pseudo Targets Generation Module together with Instruction-based Knowledge Distillation; the first creates surrogate supervision signals that let the model rehearse earlier modalities under later task formats, while the second transfers modality-specific knowledge via instruction alignment.

If this is right

  • MLLMs can retain captioning and question-answering performance on earlier modalities even after new modalities and task formats are introduced.
  • Instruction-based distillation allows preservation of modality-specific behavior without storing raw past data.
  • The approach separates the handling of task-type forgetting from modality forgetting, allowing modular extension to additional modalities.
  • Average accuracy across the sequence of tasks rises compared with replay-free or modality-incremental baselines.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same pseudo-target and distillation pattern could be tested on sequences that also include text-only or sensor-data tasks.
  • If the pseudo-target generator itself is made task-adaptive, the method might scale to longer task sequences without additional hyper-parameters.
  • The framework suggests that modality-specific instruction tuning can serve as a lightweight rehearsal mechanism for any multimodal model that must evolve over time.

Load-bearing premise

The six-task benchmark is representative of the full range of modality and task-type shifts that will occur in practice, and the added modules do not degrade performance on newly introduced modalities or tasks.

What would settle it

A follow-up experiment on a different collection of modality-task pairs in which MoInCL shows no improvement over baselines or produces lower accuracy on the newest tasks would falsify the central claim.

Figures

Figures reproduced from arXiv: 2412.13050 by Mingrui Liu, Shentong Mo, Shijian Deng, Weiguo Pian, Yapeng Tian, Yunhui Guo.

Figure 1
Figure 1. Figure 1: Illustration of our proposed Modality-Inconsistent Continual Learning (MICL), a novel and practical [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Overview of our proposed MoInCL, which mainly consists of a Multimodal Large Language Model [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Qualitative results of the Fine-tuning method in Order 2. The sample is randomly selected from the test [PITH_FULL_IMAGE:figures/full_fig_p015_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Qualitative results of the LwF (Li and Hoiem, 2017) method in Order 2. The sample is randomly selected from the test set of Task 1 (Image Captioning). The results are generated using models trained after after (a) Task 1, (b) Task 2, (c) Task 3, (d) Task 4, (e) Task 5, and (f) Task 6. 15 [PITH_FULL_IMAGE:figures/full_fig_p015_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Qualitative results of the EWC (Kirkpatrick et al., 2017) method in Order 2. The sample is randomly selected from the test set of Task 1 (Image Captioning). The results are generated using models trained after after (a) Task 1, (b) Task 2, (c) Task 3, (d) Task 4, (e) Task 5, and (f) Task 6. Describe the image. A man in a red jacket plays the guitar on the sidewalk. (a) Describe the image. A man in a red ja… view at source ↗
Figure 6
Figure 6. Figure 6: Qualitative results of the EWF (Xiao et al., 2023) method in Order 2. The sample is randomly selected from the test set of Task 1 (Image Captioning). The results are generated using models trained after after (a) Task 1, (b) Task 2, (c) Task 3, (d) Task 4, (e) Task 5, and (f) Task 6. 16 [PITH_FULL_IMAGE:figures/full_fig_p016_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Qualitative results of the PathWeave (Yu et al., 2024) method in Order 2. The sample is randomly selected from the test set of Task 1 (Image Captioning). The results are generated using models trained after after (a) Task 1, (b) Task 2, (c) Task 3, (d) Task 4, (e) Task 5, and (f) Task 6. Describe the image. A man in a red jacket plays the guitar on the sidewalk. (a) Describe the image. A man in a red jacke… view at source ↗
Figure 8
Figure 8. Figure 8: Qualitative results of our proposed MoInCL in Order 2. The sample is randomly selected from the test set [PITH_FULL_IMAGE:figures/full_fig_p017_8.png] view at source ↗
read the original abstract

In this paper, we introduce Modality-Inconsistent Continual Learning (MICL), a new continual learning scenario for Multimodal Large Language Models (MLLMs) that involves tasks with inconsistent modalities (image, audio, or video) and varying task types (captioning or question-answering). Unlike existing vision-only or modality-incremental settings, MICL combines modality and task type shifts, both of which drive catastrophic forgetting. To address these challenges, we propose MoInCL, which employs a Pseudo Targets Generation Module to mitigate forgetting caused by task type shifts in previously seen modalities. It also incorporates Instruction-based Knowledge Distillation to preserve the model's ability to handle previously learned modalities when new ones are introduced. We benchmark MICL using a total of six tasks and conduct experiments to validate the effectiveness of our MoInCL. The experimental results highlight the superiority of MoInCL, showing significant improvements over representative and state-of-the-art continual learning baselines.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 0 minor

Summary. The paper introduces Modality-Inconsistent Continual Learning (MICL), a new continual learning scenario for Multimodal Large Language Models involving simultaneous shifts in input modalities (image/audio/video) and task types (captioning/question-answering). It proposes MoInCL, which uses a Pseudo Targets Generation Module to address forgetting from task-type changes on seen modalities and Instruction-based Knowledge Distillation to maintain performance on prior modalities when new ones are added. The method is evaluated on a six-task benchmark and asserted to outperform representative and state-of-the-art continual learning baselines.

Significance. If the empirical claims hold after detailed validation, the work would be significant for defining and tackling a realistic MICL setting that combines modality and task-type shifts, both known drivers of forgetting in MLLMs. The two proposed modules target these shifts specifically, and the six-task benchmark could serve as a useful testbed if it adequately exercises the inconsistencies without hidden trade-offs on new modalities.

major comments (1)
  1. [Abstract] Abstract: the central claim that 'the experimental results highlight the superiority of MoInCL, showing significant improvements over representative and state-of-the-art continual learning baselines' is unsupported by any metrics, baseline names, task descriptions, ablation results, or statistical tests. This is load-bearing for the paper's main contribution, as the soundness of the two modules cannot be assessed without quantitative evidence.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for highlighting the need for quantitative support in the abstract. We agree this strengthens the presentation and will revise accordingly while noting that the full experimental details appear in the body of the manuscript.

read point-by-point responses
  1. Referee: [Abstract] Abstract: the central claim that 'the experimental results highlight the superiority of MoInCL, showing significant improvements over representative and state-of-the-art continual learning baselines' is unsupported by any metrics, baseline names, task descriptions, ablation results, or statistical tests. This is load-bearing for the paper's main contribution, as the soundness of the two modules cannot be assessed without quantitative evidence.

    Authors: We agree that the abstract would benefit from including specific quantitative evidence to support the superiority claim. The manuscript body (Sections 4 and 5) already provides the six-task benchmark details, baseline names (e.g., standard CL methods and SOTA variants), metrics, and ablation studies, but these are not referenced in the abstract. We will revise the abstract to incorporate key results, such as average accuracy gains and task-specific improvements, to make the central claim self-contained and substantiated. revision: yes

Circularity Check

0 steps flagged

No significant circularity

full rationale

The paper introduces a new MICL scenario and two modules (Pseudo Targets Generation Module, Instruction-based Knowledge Distillation) whose effectiveness is asserted via six-task experiments on MLLMs. No equations, algorithmic derivations, fitted parameters renamed as predictions, or self-citations appear in the provided text. The central claims rest on empirical comparisons to baselines rather than any reduction to inputs by construction, self-definition, or load-bearing self-citation chains. This is a standard empirical engineering contribution whose validation is external to the method definition itself.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Only the abstract is available; no explicit free parameters, axioms, or invented entities are stated. The central claim rests on the empirical effectiveness of the two introduced modules and the representativeness of the six-task benchmark.

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