Similarly, one could plausibly anticipate that larger, more complex, amino acids would present a greater challenge to machine learning as more noisy spectra provide a challenging space for ML algorithms to distinguish patterns. We do not observe this. Rather we see a lack of correlation between size and prediction accuracy, and even (for one measurement and library) the opposite. As for polarity/hydrophobicity, intuition is less clear. Again however, the empirical data show no discernible pattern between this physicochemical property and prediction accuracy.