What models and software are suited to modelling human decision making? I'd like to model a set of processes. The processes in question are related to human-decision making, so the model will need a measure of input, processing, and then, finally, output.
Ideally, the model would be implemented in something like R (which I know quite well) or Python (which I know less well). 
Questions:


*

*Where is the best place to start with something like this? 

*What tools are available?

*What software or language is suited to writing the model in?

*What method would be suited to testing that model against data I've collected from real humans?

 A: For models of speeded decision tasks, check out the diffusion model and the linear ballistic accumulator; Donkin et al (2011, pdf) provide a good overview of these models and their different behaviours. There is R code out there for both these models. You might also do a literature search using the keyword "Decision Field Theory", which seems to be a specific instantiation of the principles of diffusion models for high-level decisions like consumer choices, etc (in contrast, the diffusion model proper and linear ballistic accumulator are more typically used for simpler perceptual discrimination tasks). Finally, possibly related are Neural Field models.
For models of semantics, check out BEAGLE. For a related model of memory encoding/retrieval, check out Mehort & Johns (2005, pdf)'s Iterative Resonance Model.
A: Have you thought about agent based modeling/social simulation? It's not that clear from your question what exactly you're trying to achieve but ABM may be suitable for your purposes as it does lend itself to modelling human decision making as you can programme agents with different characteristics. It's also very good for spatial problems.
You could either use the data you have already gained on the population under study and use that to programme your agents and then you can forecast into the future and compare to what happens in the real life population. This can be repeatedly tested with different environmental factors say with an economic model on the decision to invest with the environmental effect of different tax rates. Alternatively you could set up a model and compare it to your real life data.
While chapter 26 of The R Book is on Simulation Models you may be better off with Netlogo than with R which is also free and especially designed for agent based modelling.
http://ccl.northwestern.edu/netlogo/
The Journal of Artificial Societies and Social Simulation is a great open source journal covering this area.
http://jasss.soc.surrey.ac.uk/JASSS.html
