Noise decreases the number of phenotypes accessible by real-valued networks.

<p>Number of unique phenotypes <i>U</i> accessed for different numbers of gene expression states <i>k</i> and varying degrees of noise <i>σ</i>, for (A) random networks and (B) networks pre-selected for stability. Networks are real-valued, <i>W</i>_<i>r</i>, network size <i>N</i> = 4, <i>s</i>_off = 0, maximum of <i>T</i> = 100 iterations, and sample size <i>λ</i> = 1.7 × 10⁶. Jitter was added to values on the x-axis to avoid overlap of markers. Dashed lines represent the size of phenotype space: _<i>max</i> = <i>k</i>⁴.