Former Sony research and development director Attila Vass lists work on the "Next Generation PlayStation" from 2010 to 2012 through his LinkedIn profile.
Vass's work was for the system's graphics library and security. He had previously worked on those areas and others for the PlayStation 2, PSP, PS3 and Vita.
The CV shows that Sony has been working on its next generation hardware since at least August 2010.
Earlier this year alleged specs for Sony's next PlayStation console, codenamed 'Orbis', were leaked online.
The PlayStation 4 is expected to launch in 2013, and Sony has said that the firm is confident its console will be released before Microsoft's next Xbox.
Sony recently purchased cloud-gaming service Gaikai, which is rumoured to allow full PlayStation backwards compatibility and may possibly become a crucial part of Sony's next system.