In order to reduce the repetitive investment in the competition for subsequent improvements to the patented technology, the prospect theory implies that widening patents scope is necessary for the initial inventors. On the contrary, the post-invention competition theory suggests that narrowing patent scope could retain more incentives for subsequent improvements. Rent dissipation theory proposes that invention competition prior to the granting of broad patents would probably result in rent dissipation; it has not been paid the adequate attention by prospect theory. It is suggested that although prospect theory has dominated the academic research on patent scope as well as patent policy in some countries, new factors and perspectives should be considered for pursuing optimal patent scope in order to promote the innovation in the new fields of technology.