當代教育中，合作問題解決(Collaborative Problem Solving, CPS)已成為 二十一世紀學生不可或缺的核心能力之一。2025 年，國際學生能力評量計畫 (Program for International Student Assessment, PISA)提出的「數位世界中的學習」 (Learning in the Digital World)強調運用計算工具進行學習的重要性，因此， 「在數位世界中共同學習」(co-learn)成為本研究的核心概念。過去關於 CPS 的 研究多半依賴行為表現與自陳式量表來評估學生的學習成效，但這類方法常被批 評具有主觀性，且缺乏即時性與準確性。既有的數位 CPS 研究亦顯示，對於任務 難度如何影響學習者的心理狀態(包含心理負荷、投入程度、情緒與疲勞)以及 腦際同步(inter-brain synchrony, IBS)的探討仍存在研究缺口。本研究旨在透過 神經生理指標，探討任務需求、心理負荷與參與者之間神經同步性之動態關係， 以填補上述研究缺口。為了檢驗任務難度是否會影響數位 CPS 的表現，本研究進 行了一項腦波同步量測(Hyperscanning EEG)實驗，共招募四十組雙人組 (dyads)，參與三種不同難度層級(簡單、中等與困難)的問題解決任務。首先， 我們計算三種任務的通過率;接著，利用 EEG 指標評估心理負荷、投入程度、情 緒與疲勞狀態，並以加權相位延遲指數(weighted Phase Lag Index, wPLI)量測成 對參與者之間的腦際同步。此外，也蒐集任務完成時間等行為資料，並與生理指 標進行關聯分析。在行為結果方面，從簡單到困難任務，其完成時間(秒)與通 過率分別為:252.55 秒(90%)、498.40 秒(45%)以及 558.40 秒(32.5%)。在 生理結果方面，我們發現中等難度任務下的腦際同步程度最高，而簡單與困難任 務則呈現較低的 IBS 水準。任務難度與 IBS 之間呈現非線性關係，符合 Yerkes- Dodson 定律。此外，研究結果亦顯示，額葉、頂葉與顳葉在數位 CPS 的歷程中 扮演重要角色。總結而言，本研究運用 Hyperscanning EEG 技術，為數位世界中 合作問題解決的歷程提供了客觀的神經生理證據。

Collaborative Problem Solving (CPS) has become a crucial skill for students in the 21st century due to its increasing importance in education. In 2025, “Learning in the Digital World,” proposed by the Program for International Student Assessment (PISA) 2025, highlights the significance of learning with computational tools. Therefore, “co-learn” in the digital world is the main concept introduced in this study. Previous research mainly relied on behavioral outcomes and self-reported measures to assess students’ learning in CPS. However, these measures were often criticized for being subjective and lacking real-time accuracy. Past studies on digital CPS reveal research gaps regarding how task difficulty influences mental states, including mental workload, engagement, emotion, and fatigue, as well as inter-brain synchrony in such environments. This study aims to address this gap by using neurophysiological measures to examine the dynamic relationship between task demands, mental workload, and neural synchrony among participants. To determine whether task difficulty affects the outcomes of digital CPS, we conducted a Hyperscanning Electroencephalography (EEG) experiment involving forty dyads engaged in three types of problem-solving tasks with varying difficulty levels: easy, intermediate, and hard. First, we calculated the passing rates of three tasks. Then, EEG indices were used to assess mental workload, engagement, emotion, and fatigue, while the weighted Phase Lag Index (wPLI) was used to measure inter-brain synchrony (IBS) between pairs. Furthermore, behavioral data on task completion time were collected to correlate with physiological results. For behavioral data, the results showed that from the easy to the difficult level, the completion time (seconds) and passing rates are 252.55 (90%), 498.40 (45%), and 558.40 (32.5%). For the physiological results, we found that in intermediate difficulty, IBS is at the highest level. In contrast, both easy and difficult tasks were associated with lower IBS levels. The nonlinear relationship between task difficulty and IBS follows the Yerkes-Dodson law. We also found that frontal, parietal, and temporal regions are associated with the process of digital CPS. In conclusion, our study used the technique of Hyperscanning EEG to provide objective evidence during the process of CPS in the digital world.