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Generative artificial intelligences like ChatGPT or Google Bard are reshaping how we write. But how can we tell if a passage comes from a human mind or an algorithm? A research team built a machine‑learning model that can differentiate student‑written texts from those produced by five different LLMs. The approach uses two steps: binary classification (human vs. AI) and multiclass classification (human vs. each of the five models). They tested traditional algorithms such as Random Forest and recurrent neural networks, achieving 98.5% accuracyβ€”far higher than the well‑known GPTZero (78.3%).

To understand *why* the model works, the authors applied Explainable AI (XAI), which highlights the most decisive features for each decision. These include sentence length, lexical variety, and recurring syntactic patterns. Such β€œstylistic fingerprints” create a unique profile for every author, human or artificial, aiding plagiarism detection and ensuring content originality. In practice, the system not only says β€œit’s AI” but also explains which traits led to that conclusion. This approach could become a key tool for schools, publishers, and online platforms, where transparency about text provenance is increasingly vital.

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The proposed approach blends supervised classification techniques with interpretable feature analysis. Random Forest, thanks to its ability to handle heterogeneous data, provides variable importance based on reduced impurity, highlighting which attributes (e.g., n‑grams, readability scores, rare word frequency) most contribute to the distinction. RNNs, particularly LSTM networks, capture long‑term dependencies in the text flow, allowing detection of recurring patterns typical of LLMs, such as a tendency to produce balanced yet less variable sentence structures. XAI, implemented via SHAP (SHapley Additive exPlanations), assigns each feature a positive or negative contribution value for the prediction. Examining average SHAP values per class revealed that LLMs tend to use a more uniform distribution of common words, whereas students exhibit spikes of specialist vocabulary linked to academic context. Moreover, lexical cohesion (measured with Coh‑Metrix) is higher in AI‑generated texts, likely due to coherence‑optimizing algorithms. These findings not only boost classifier accuracy but also provide a theoretical basis for developing more robust textual authenticity metrics, useful in educational and publishing settings.

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Authors:
Ayat A. NajjarHuthaifa I. AshqarOmar DarwishEman Hammad
Date Published:
Original Article www.mdpi.com
Fact-check verified on 27/04/2026
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Creative Commons License CC BY-NC-SA 4.0

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