## 2 Experiment 1: LLM Text Personalization
### Results Experiment 1
#### 2.3.2 Main Effect of LLMs  
The main effect of the models was significant. Linguistic features of modifications from different LLMs differed regardless of reader characteristics. See Table 6 for descriptive statistics and F-values. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Linguistic Features** & \multicolumn{2}{c}{**Claude**} & \multicolumn{2}{c}{**Llama**} & \multicolumn{2}{c}{**Gemini**} & \multicolumn{2}{c}{**ChatGPT**} & \multicolumn{2}{c}{**Main Effects of LLMs**} \\ \cline{2-11}  & **M** & **SD** & **M** & **SD** & **M** & **SD** & **M** & **SD** & **F (3, 320)** & \(p\)** & \(\eta^{2}\) \\ \hline
**FKGL** & 11.13 & 4.34 & 11.87 & 3.18 & 11.23 & 3.91 & 11.72 & 3.53 & 3.35 & 0.02 & 0.03 \\
**Academic Writing** & 44.43 & 34.11 & 54.14 & 32.34 & 45.47 & 34.45 & 45.34 & 31.29 & 4.70 & 0.01 & 0.05 \\
**Idea Development** & 59.97 & 22.63 & 33.77 & 16.90 & 51.52 & 23.93 & 52.91 & 30.29 & 19.58 & \textless{}0.001 & 0.17 \\
**Sentence** & 30.38 & 24.15 & 60.86 & 24.71 & 52.65 & 25.32 & 51.06 & 31.06 & 20.30 & \textless{}0.001 & 0.17 \\
**Noun-to-Verb Ratio** & 2.25 & 0.80 & 2.11 & 0.48 & 2.06 & 0.43 & 2.03 & 0.43 & 6.27 & \textless{}0.001 & 0.06 \\
**Sentence Length** & 14.71 & 3.91 & 18.68 & 5.06 & 18.55 & 4.25 & 18.73 & 6.22 & 17.68 & \textless{}0.001 & 0.16 \\
**Language Variety** & 47.61 & 28.43 & 38.07 & 27.84 & 55.51 & 25.77 & 49.64 & 25.68 & 12.21 & \textless{}0.001 & 0.11 \\
**Sophisticated Word** & 46.21 & 31.90 & 46.55 & 26.74 & 47.58 & 30.07 & 47.43 & 32.51 & 0.15 & 0.93 & 0.00 \\
**Academic Frequency** & 7851.69 & 1465.06 & 9420.10 & 1569.22 & 8646.06 & 1291.46 & 8342.75 & 1412.02 & 21.48 & \textless{}0.001 & 0.18 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Descriptive statistics and main effects of LLMs. Source: authors’ contribution. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Reader 1**} & \multicolumn{2}{c}{**Reader 2**} & \multicolumn{2}{c}{**Reader 3**} & \multicolumn{2}{c}{**Reader 4**} & \multicolumn{2}{c}{**Main Effects of Profile**} \\ \cline{2-11}  & **(High RS/High PK *)** & **(High RS/Low PK *)** & **(Low RS/High PK *)** & **(Low RS/Low PK *)** & **(Low RS/Low PK *)** & **(Low RS/Low PK *)** & **Main Effects of Profile** \\ \cline{2-11}  & **M** & **SD** & **M** & **SD** & **M** & **SD** & **M** & **SD** & **F (3, 320)** & \(p\)** & \(\eta^{2}\) \\ \hline
**FKGL** & 16.97 & 2.36 & 10.63 & 1.76 & 9.84 & 1.89 & 8.50 & 1.39 & 355.64 & \textless{}0.001 & 0.79 \\
**Academic Writing** & 89.93 & 12.53 & 45.08 & 24.86 & 37.20 & 23.25 & 17.17 & 15.95 & 228.05 & \textless{}0.001 & 0.70 \\
**Idea Development** & 57.38 & 28.05 & 47.40 & 25.37 & 48.19 & 23.94 & 45.19 & 23.95 & 4.97 & 0.002 & 0.05 \\
**Sentence** & 55.00 & 32.55 & 50.30 & 29.19 & 40.85 & 23.96 & 48.81 & 26.84 & 2.67 & 0.04 & 0.03 \\
**Cohesion** & & & & & & & & & & & \\
**Noun-to-Verb Ratio** & 2.81 & 0.62 & 1.93 & 0.25 & 1.84 & 0.31 & 1.87 & 0.25 & 133.37 & \textless{}0.001 & 0.58 \\
**Sentence Length** & 20.91 & 6.59 & 18.70 & 4.46 & 14.75 & 3.27 & 16.31 & 3.64 & 30.42 & \textless{}0.001 & 0.24 \\
**Language Variety** & 75.75 & 21.26 & 54.07 & 21.43 & 27.14 & 18.46 & 33.88 & 18.85 & 112.79 & \textless{}0.001 & 0.54 \\
**Sophisticated Word** & 90.23 & 9.97 & 42.87 & 19.35 & 31.17 & 17.71 & 23.50 & 13.59 & 342.11 & \textless{}0.001 & 0.78 \\
**Academic Frequency** & 9591.39 & 1425.57 & 8708.02 & 1328.34 & 7763.13 & 1426.14 & 8016.06 & 1308.47 & 30.42 & \textless{}0.001 & 0.24 \\ \hline \hline \end{tabular}  
* RS = reading skills; PK = prior knowledge.  
\end{table} 
Table 5: Descriptive statistics and main effects of reader profiles. Source: authors’ contribution. [PERSON]'s modifications (\(M\) = 11.87, \(SD\) = 3.18) had significantly higher FKGL compared to modifications by Claude (\(M\) = 11.13, \(SD\) = 4.34), \(p\) < 0.05. [PERSON]'s modifications are significantly higher in academic writing and academic wording compared to modifications by Claude, Gemini, and ChatGPT (all \(p\) < 0.05).