After publication of (Abrams 2013), I discovered errors in two formulas in the settle-nets paragraphs of the POPCO main loop section in Methods (page 13 in the PDF file). I correct these errors here. In the definition of the weighted sum ni of input activations aj from nodes j to node i across links with weights wij, the direction of the inequality was reversed. The definition of ni should read: (Formula presented.). There were also errors in the definition of si, the weighted sum of a node’s current activation ai and its summed inputs pi and ni across positively and negatively weighted links, respectively. The definition of si should read as follows: (Formula presented.). I regret these errors and hope that they do not cause confusion. Full source code for the version of POPCO used in Abrams (2013) can be found at https://github.com/mars0i/ popco.