SRD: Reinforcement-Learned Semantic Perturbation for Backdoor Defense in VLMs

Vision-Language Models (VLMs) have achieved remarkable performance in image captioning, but recent studies show they are vulnerable to backdoor attacks. Attackers can inject imperceptible perturbations-such as local pixel triggers or global semantic phrases-into the training data, causing the model to generate malicious, attacker-controlled captions for specific inputs. These attacks are hard to detect and defend due to their stealthiness and cross-modal nature. By analyzing attack samples, we identify two key vulnerabilities: (1) abnormal attention concentration on specific image regions, and (2) semantic drift and incoherence in generated captions. To counter this, we propose Semantic Reward Defense (SRD), a reinforcement learning framework that mitigates backdoor behavior without prior knowledge of triggers. SRD uses a Deep Q-Network to learn policies for applying discrete perturbations (e.g., occlusion, color masking) to sensitive image regions, aiming to disrupt the activation of malicious pathways. We design a semantic fidelity score as the reward signal, which jointly evaluates semantic consistency and linguistic fluency of the output, guiding the agent toward generating robust yet faithful captions. Experiments across mainstream VLMs and datasets show SRD reduces attack success rates to 5.6%, while preserving caption quality on clean inputs with less than 10% performance drop. SRD offers a trigger-agnostic, interpretable defense paradigm against stealthy backdoor threats in multimodal generative models.

Research on the Laws of Multimodal Perception and Cognition from a Cross-cultural Perspective -- Taking Overseas Chinese Gardens as an Example

This study aims to explore the complex relationship between perceptual and cognitive interactions in multimodal data analysis,with a specific emphasis on spatial experience design in overseas Chinese gardens. It is found that evaluation content and images on social media can reflect individuals' concerns and sentiment responses, providing a rich data base for cognitive research that contains both sentimental and image-based cognitive information. Leveraging deep learning techniques, we analyze textual and visual data from social media, thereby unveiling the relationship between people's perceptions and sentiment cognition within the context of overseas Chinese gardens. In addition, our study introduces a multi-agent system (MAS)alongside AI agents. Each agent explores the laws of aesthetic cognition through chat scene simulation combined with web search. This study goes beyond the traditional approach of translating perceptions into sentiment scores, allowing for an extension of the research methodology in terms of directly analyzing texts and digging deeper into opinion data. This study provides new perspectives for understanding aesthetic experience and its impact on architecture and landscape design across diverse cultural contexts, which is an essential contribution to the field of cultural communication and aesthetic understanding.