Gravity darkening value as a function of the primary potential, where each point represents an individual binary model. For each model the gravity darkening exponent was determined randomly (between 0.0 and 1.0) and a model generated by fitting the light factor and potential, whilst keeping all other parameters fixed. The points are coloured by the χ²goodness of fit to demonstrate that the outliers are a consequence of an inadequate fit (the lower χ²values denote the better models, here depicted in black).