Differential equations in psychology I am wondering (and searching with no success) if there are any examples of differential equations in psychology? 

I mean, no tutorial explaining what is differenetial equations or even partial differential equations, but a research (like in emotions or social psychology, or cognitive psychology) by psychologists that use these equations to model the data? 

[update, 29.05.2016] Stack Community always reminds me that the quality of the answers depends on the question asked. Just as a good question is half of the problem.
I'll try to make myself clear with an example. I thought about an article in psychology, say about cognitive dissonance, emotions, coping or else, that use differential equations to decribe phenomenon without invoking physics or chemistry or other hard science. Article by Deboeck &amp; Bergeman introduces pendulum model(Christiaan's comment). But I don't have to refer to physics when doing ordinary squares regression, so that's why I thought it is possible to use differential equations without explicite references to physical models. 

June 2, 2016: I never suggested we could "use differential equations without explicit reference to physical models". I have always said the same: the mathematical interpretation of cellular processes has lost prominence (owing to further research). The biological processes obviously remain; the interpretation has not been able to hold.  Teresa Pelka
The Hodgkin and Huxley model of neuronal firing is based on non-linear differential equations. A significant portion of research on sensation and perception is based on such models.