Johns Hopkins School of Medicine

Dr. Dolen reports in Nature that the neuromodulators oxytocin and serotonin act in concert to make social interactions rewarding. In addition, these studies suggest that this type of reinforcement learning may not function properly in the brains of autistic individuals. 

Dolen G, Darvishzadeh, A, Huang, KW, Malenka RC. (2013). Social reward requires coordinated activity of nucleus accumbens oxytocin and serotonin.  Nature Vol 501, pp179-184.

In the news:
http://www.cell.com/abstract/S0092-8674(13)01209-9?utm_source=ECE001&utm_campaign=&utm_content=&utm_medium=email&bid=L41FE5F http://healthland.time.com/2013/09/12/what-the-love-hormone-has-to-do-with-autism/