# Vocabulary Retention Under Multimodal Coupling Strength Index (MCSI): Insights from Eye Tracking
## 1 Introduction  
Vocabulary acquisition is essential for mastering any language, and researchers have developed various techniques to improve it. Traditional approaches often involve repetitive memorization, which tends to be tedious and less effective for lasting memory. Newer studies indicate that combining different senses--like seeing pictures while hearing words--makes vocabulary stick better in memory. Research by [PERSON] shows that without reinforcement, people forget words quickly, remembering only about 33% after one day [1]. [PERSON], [PERSON] mentioned that although learning words in meaningful sentences improves retention by activating meaning-related brain networks, this method still relies on just one type of input, missing the opportunity to engage the brain's natural ability to process multiple senses together [2].  
Brain research by [PERSON] et al. reveals that a specific area called the superior temporal sulcus (STS) acts as a central hub where sights and sounds come together [3]. This biological process supports the Dual-Coding Theory mentioned by [PERSON] [4], which explains why combining images and sounds strengthens memory--it creates two linked mental records. Modern eye-tracking technology now allows us to measure exactly where people look while learning, giving new insights into how multisensory learning works.  
Although we have strong theories, current studies still have gaps. Most importantly, there are no good ways to measure in real time how single-sense learning (like just seeingimages) compares to multi-sense learning (seeing and hearing together) for vocabulary. Also, existing research mainly uses simple performance measures that do not reveal how the brain combines sights and sounds to boost learning. To address these gaps, this study introduces a novel Multimodal Coupling Strength Index (MCSI) that synergizes eye-tracking metrics with memory performance, thereby establishing a real-time indicator of audiovisual integration efficiency.  
The core research aims to resolve two pivotal questions: Firstly, how do unimodal (auditory-only, visual-only) and multimodal (audiovisual) conditions comparatively influence lexical memory? Secondly, can the proposed MCSI model dynamically quantify and validate crossmodal integration efficiency during vocabulary learning? To address these questions, we implement a rigorous experimental design comparing four sensory conditions: Group A (no sound and image), Group B (image-only), Group C (sound-only), and Group D (sound and image).  
The study makes key advances: It is the first to directly compare these four learning conditions using eye tracking to understand the cognitive processes. The MCSI model is a new tool that combines attention shifts (how eyes move) and memory results to precisely measure the synergy between senses. Our results also provide strong evidence for brain-based learning theories by showing how eye movements link to memory success.  
The article systematically unfolds these contributions across five sections. Following this Introduction, Section 2 synthesizes the theoretical foundations and identifies research gaps. Section 3 details the experimental methodology, including eye-tracking protocols and MCSI formulation. Section 4 presents empirical findings on memory accuracy and multimodal integration effects. Section 5 discusses theoretical implications and practical applications, while Section 6 addresses limitations and future research directions.