 argue that Losada's conclusions in previous papers using modelling from fluid dynamics, and those in his paper co-authored with Fredrickson, are not only based on poorly-reported experiments – they argue that it is difficult to draw any conclusions from some previous studies by Losada because critical details are omitted, and "interpretations of results are made with little or no justification" (p. 5) – but are based on elementary errors in the use of differential equations.Fredrickson and others hypothesize that positive emotions undo the cardiovascular effects of negative emotions.When people experience stress, they show increased heart rate, higher blood sugar, immunosuppression, and other adaptations optimized for immediate action.