We report experimental results on one-shot two person 3x3 constant sum games played by non-economists without previous experience in the laboratory. Although strategically our games are very similar to previous experiments in which game theory predictions fail dramatically, 80% of actions taken in our ex- periment coincided with the prediction of the unique Nash equilibrium in pure strategies and 73% of actions were best responses to elicited beliefs. We argue how social preferences, presentation effects and belief elicitation procedures may influence how subjects play in simple but non trivial games and explain the diferences we observe with respect to previous work.Experimental Funding was provided by the ESRC Centre for Evolutionary Learning and Social Evolution (ELSE) and Ministerio de Ciencia y Tecnología (BEC2003-01131). Financial support from Generalitat de Catalunya (2005SGR-00836) and Barcelona Economics-XREA is gratefully acknowledged.