Hi everyone, I'm having trouble figuring out how to check a model for curvilinearity in SPSS. The data involves cortisol (stress hormone) and fMRI data in response to faces. I suspect this will be a typical inverted U as cortisol frequently has that kind of effect. What is the best way to check this? Should I run a curve estimation? It's been a while since Stats class and I'm having trouble remembering how to do this.