Animal models of disease are the cornerstones of medical research, but they are inherently limited in their predictive value of complex human mental behaviors such as mood shifts or cognitive preferences. However, this fact hasn't stopped the scientific community from focusing their finite resources on improving their animal models. 

The current trend, called environmental enrichment (EE), makes the laboratory living environments more complex by outfitting them with objects that stimulate animals' mental and physical growth. The results are relatively obvious:

• The rats housed in an enriched environment had increased activity of neurotransmitters
  
• Brain morphology, an 8% increase in thickness of the cerebral cortex in some studies
  
• Increased number of neurons and synapses.
  
• Increase in the capillaries that carry nutrients and blood to the brain

Although interesting, this still does little to help us undertand human mental behavior.  It’s still impossible to ask a mouse or even a baboon if it is feeling less depressed or more assertive. 

To understand how new treatments will influence human behavior we will need to study the impacts in humans.  The lack of objective measurement tools to analyze and detect the mental health changes will be bolstered by breakthroughs in brain imaging technology and biochips. It is only with these tools that we will begin to significantly increase our knowledge of human behavior.

Update 5/7: The pharmaceutical industry spends most of it's $30B research budget aimed at central nervous system disorders using our friend, Mus musculus.